Bibliography Introduction Much of the scenic beauty of nature has been replaced by densely populated areas that sprawl for miles from urban centers. This visual pollution affects us all and leaves us with a longing for a closer connection with nature. We spend about 90 percent of our time indoors. Interior plants are an ideal way to create attractive and restful settings while enhancing our sense of well being. In addition, houseplants can be a satisfying hobby and can help purify the air in our homes. Indoor plants not only convert carbon dioxide to oxygen, but they also trap and absorb many pollutants. Many of these chemical compounds, which are released into our air through a process called “off-gassing,” come from everyday items present in our homes and offices. To be a successful indoor gardener, you need to understand how the interior environment affects plant growth and how cultivation differs from growing plants outdoors. Factors Affecting Plant Growth Plant growth is affected by light, temperature, humidity, water, nutrition, and soil. Light Of all of the factors affecting plant growth in interiors, adequate light is by far the most important. Light is needed for plants to produce food and survive — generally, the more light available, the more food produced for growth.

Light is measured in units called foot candles. One footcandle (ft-c) is the amount of light cast by a candle on a white surface 1 foot away in a completely dark room. Outdoors, the light levels on a bright day range from 10,000 ft-c in an open sunny area to 250 ft-c or less in the shade of a large tree. It is very helpful to have a general idea of how much light is present in a given location in your house. You can get a fairly good estimate with a handheld light meter, or you can use a 35 mm camera and do the following: Set the film speed indicator to ASA 25 and the shutter speed to 1/60th second. Place a piece of white paper where you want to measure the light levels, aim the camera toward the paper close enough to fill the view, and adjust the f/stop so that the meter indicates a correct exposure. Read the approximate light level from Table 1. Table 1.

Indoor light levels and appropriate f/stop settings f/stop Setting f/16 2,400 ft-c With the help of this table, you can obtain the light intensity reading from anywhere in your home. For example, if the f/stop setting is f/16, the approximate light level is 2,400 ft-c. Using the light readings, your home can be divided into four areas, which have the following light levels for 8 hours per day: Low-light areas: 25 ft-c – 75 ft-c Medium-light areas: 75 ft-c – 200 ft-c High-light areas: over 200 ft-c but not direct sunlight Sunny light areas: at least 4 hours of direct sunlight Figure 1. Many foliage plants are native to tropical rain forests, where light levels are low. These plants can be easily injured if exposed to strong light. Symptoms of over-exposure are upright leaves and bleached, scorched leaves. Do not place high-light sensitive plants in direct sunlight (on a porch or in front of a window).

In this example, Chinese Evergreen (Aglaonema) and Dumb Cane (Dieffenbachia) show symptoms of high-light damage. In your home, the amount of light in a given location is variable — it is affected by the presence of trees outdoors (may shade at certain times), roof overhangs (may shade at certain times), wall color (reflectance), window curtains, day length, time of day, and time of year. When shopping for indoor plants, select plants for a given location based on the approximate light levels in the spot. The plant’s label will usually contain information on the light requirements of the plant. If the plant label lists “high light” but the selected area in the home does not provide adequate light, artificial light sources such as fluorescent and/or special incandescent lights may be used to supplement the natural light. Increasing the number of hours of light exposure can also help—for example, 16 hours of light and 8 hours of dark. This extends the number of hours during which plants receive light. While adequate light is crucial for plant growth, too much light can be damaging (Figure 1). Indoor plants are classified according to the amount of light needed for growth.

(A list of plants and their light requirements is provided in Table 3.) Look for this information in general terms on the plant’s label: Low: minimum 25 ft-c – 75 ft-c, 75ft-c – 200 ft-c for good growth Medium: minimum 75 ft-c – 150 ft-c, 200 ft-c – 500 ft-c preferred High: minimum 150 ft-c – 1,000 ft-c, 500 ft-c – 1,000 ft-c preferred Very high: minimum 1,000 ft-c, 1,000+ ft-c preferred Windows with eastern exposure within the home generally provide the best light and temperature conditions for most indoor plant growth because plants receive direct morning light from sunrise until nearly midday. Footcandle readings at these windows can reach 5,000-8,000. As the morning progresses, the direct sun recedes from the room. An eastern room is cooler than southern or western rooms because the house absorbs less radiant heat.

Light from the east is cooler than that from the south or the west, and thus it causes less water loss from the plants. Windows with southern exposure give the largest variation of light and temperature conditions. The low winter sun shines across the room for most of the daylight hours. In the summer, when the sun is farther north than it is in the winter, the sun rises at a sharp angle in the morning and is high in the sky by noon. Direct light comes into a south window only at midday. If there is a wide overhang covering the windows outside, the sun may not enter the room at all. The sun at noon on a summer day may measure 10,000 ft-c. Indoors, however, a southern window with wide eaves on the outside will receive about the same amount of light as a window with northern exposure. Southern and western exposures are interchangeable for most plants. In the winter, most plants, except those with definite preference for northern exposure, can be placed in a room with southern exposure. Windows with northern exposure provide the least light and the lowest temperature. Because the United States is in the northern hemisphere, it receives most of its sunlight from the south.

Out of the four exposures, the northern exposure receives the least light and heat year round. Figure 2. Within your home, changes in natural light penetration occur with the seasons. Because of the low-light levels, maintaining healthy plants can be a challenge. A northern windowsill can measure light levels as low as 200 ft-c on a clear winter day, which is optimal for some plants, such as the African violet. This exposure is best for plants with green foliage because the coloration on variegated foliage tends to disappear under low-light conditions. Although most plants grown indoors will not grow in a northern room, they may tolerate it for short periods of time. Seasons change the amount of natural light entering through windows. For example, the summer sun reaches a higher zenith compared to the winter sun (Figure 2). Therefore, sunlight penetrates farther into a room during winter. How can you tell if your plant is not receiving adequate light? The plant does not grow. The internodes (spaces between the leaves) on the new growth are much longer than the internodes on the older part of the plant. The new leaves are smaller than the older leaves. The leaf color is a lighter green on the newer foliage than on the older foliage.

The older leaves are dead. Temperature Temperature is the second most important factor influencing plant growth in interior environments. People feel comfortable in the range of 72 degrees F-82 degrees F, and interior plants can tolerate and grow well in the 58 degrees F-86 degrees F range because most indoor plants originate from tropical and subtropical areas of the world. Temperature and light are linked through the processes of photosynthesis and respiration. These processes can be thought of as the “yin and yang” of plant life — two parts of a circle. Photosynthesis builds sugars and starch, which are then broken down by respiration to provide energy for the development of new tissues (growth) and the maintenance of existing ones. High temperature speeds up respiration. If the plant is not producing sufficient sugars (as under low light), then high temperatures may break down what little sugars are made, leaving little to none for growth. Maintenance takes precedence over growth; therefore, under insufficient light, plants do not grow. If light is so low that sugars produced are insufficient for maintenance, the plant eventually dies. When sugar levels are low, the plant takes nutrients and sugars from older leaves to maintain new leaves.

To help plants in an indoor environment, two options are available: (1) raise light levels to increase photosynthesis and sugar production or (2) reduce night temperature to lower respiration rates and allow more sugars for growth. What temperatures are likely to occur in homes? During the summer, air conditioning that may have been turned off at night or weekend thermostat settings that may have been raised result in higher than desirable night temperatures. During the winter, heating that may have been turned off at night or weekend thermostat settings that may have been lowered may result in lower night temperatures. Be especially careful not to allow temperatures to drop below 50 degrees F, or chill damage will result on some sensitive foliage plants (e.g., Chinese Evergreen, Aglaonema). Chill damage is manifested with the yellowing of lower leaves and/or defoliation. Plants vary in their minimum and maximum temperature requirements. Examples of cool-loving plants suitable for locations where temperatures drop to the low 50s at night and 60s during the day are Cyclamen, Wonder Plant, Fatshedera, Japanese Aralia, and Fatsia. A list of plants and their temperature requirements is provided in Table 3 .

Not all interior plants have the same temperature requirements for optimal growth. For example, Cast Iron Plant, Aspidistra, and ferns actually grow better with cooler temperatures (72°F), while other tropical plants grow best if the temperatures are 90 degrees F – 95 degrees F. Such temperatures are rarely allowed indoors. The best temperature range for indoor plants is 70 degrees F – 80 degrees F day and 65 degrees F – 70 degrees F night. Relative Humidity Relative humidity is the amount of moisture contained in the air. For interior plants, relative humidity below 20 percent is considered low, 40 percent – 50 percent is medium, and above 50 percent is high. Relative humidity is a very important factor, but it is easily overlooked. In a greenhouse, relative humidity is 50 percent or higher. Rapid transpiration and water loss may result when newly purchased plants are placed in the 10 percent – 20 percent relative humidity typical of most homes (Figure 3). Most indoor plants come from the tropics where high relative humidity is common. Therefore, take the following steps to help your plants adjust to the low relative humidity in your home.

Figure 3a. The lower the humidity, the more water is lost from a leaf. At the same temperature of 70ºF, a leaf placed in 10% relative humidity loses more water compared with the leaf placed in 50% relative humidity. Figure 3b. The higher the temperature, the more water vapor the air can hold, and the more water will be lost from the plant. At the same humidity of 50%, a leaf placed in 90ºF air loses more water compared with the leaf placed in 70ºF air. Place plants close together to create a microenvironment with a higher relative humidity. Use a shallow container filled with water and lava rocks or gravel, which will provide evaporation from a large surface area and increase relative humidity. Use a humidifier. Use mist bottles to spray water around the plant; however, in reality, you would need to mist every few minutes for an indefinite amount of time to make a difference in relative humidity around the plant. The foliage and flowers of plants with hairy leaves should not be sprayed with water. Water on such leaves may stay longer, providing opportunities for disease spores to germinate.

Water Water Quantity Learning to water is one of the most important skills in plant care. Applying too much water can suffocate plant roots and too little water causes growth to become erratic and stunted. Watering frequency will depend on the conditions under which the plants are growing. When dealing with how much water to apply, consider the following: Plant type: A list of plants and their moisture requirements is provided in Table 3 . Not all plants are similar in their water requirements. This information, along with the light preference, is usually included on the plant label. For example, a croton, which prefers high light, will likely need more frequent watering compared with a succulent plant such as Opuntia cactus. Both have similar light needs but dissimilar water requirements. Plant size: Larger plants need more water compared to smaller plants. Container volume: If the growing container is too small, watering may be required more frequently. Soil moisture: The amount of water already present in the growing medium will also affect your watering frequency. Light intensity: Plants under high light transpire more water compared with plants under low light. Improper watering causes many problems. Containers with saucers may cause an excessive build-up of soluble salts (from the applied fertilizer).

High levels of soluble salts can cause damage to plant roots and a decline in growth. Discard any water that had drained in the saucer after irrigation, and apply large quantities of water to the soil to leach the accumulated soluble salts. In deciding when you should water, feel the soil by pushing a finger an inch or so below the surface. If the soil is still moist, no further water is needed. Water devices or water meters are also available to simplify watering. Water Quality The quality of the irrigation water is an issue with plants that are susceptible to fluorine and chlorine, such as Corn Plant (Dracaena), Ti Plant (Cordyline), Peacock Plant (Maranta), and Rattlesnake Plant (Calathea) (Figure 4). Alleviate this problem by letting the water stand for several days — so that some chlorine and fluorine will be released from it — before applying the water to the plants. Move susceptible plants away from the edge of the pool to prevent water splashes from reaching the foliage. Do not use susceptible plants around enclosed pools. In general, plants with long linear leaves (such as the Spider Plant) are more susceptible to fluorine. Figure 4a.

Symptoms of fluorine damage on the Corn Plant include tip and leaf scorching. Figure 4b. Symptoms of fluorine damage on the Ti Plant include tip and leaf scorching. Nutrition Many indoor gardeners have the same problem with fertilizer that they have with water — they want to give their plants too much. Danger from over-fertilization occurs because any fertilizer used, whether in liquid, powder, or tablet form, will dissolve in soil water and will form salts in the water. When you over-fertilize, the water in the soil becomes so salty that it “burns” the plant’s roots by removing water from them (Figure 5). Excess soluble salts accumulate as a whitish crust on the surface of the growing medium and/or near the rim of the container. Figure 5a. Soluble salt burn is manifested as leaf martinal and tip burn. Dead roots also invite root diseases. Figure 5b. Soluble salts can burn roots; notice that the healthy roots are white, while the dead roots are brown. Dead roots also invite root diseases.

Before feeding plants, consider the following: Plant type: Some plants are heavy feeders (e.g., Ficus species), while others need little or no additional fertilizer for months (e.g., succulents). Volume of soil: The growing medium that is present — smaller pots require less fertilizer compared with larger pots because they contain less soil. Light intensity: The higher the light levels, the more nutrients needed for plant growth. A newly purchased, healthy plant rarely needs an immediate application of fertilizer. In most cases, the amount of fertilizer applied by the commercial producer will supply enough nutrients for two to three months in the home. This rule is flexible — if deficiency symptoms are evident, fertilizer application is desirable. The secret to fertilizing plants indoors is to apply small amounts of fertilizer as the plant grows. Without new growth, the plant has a limited need for more fertilizer. During the winter when light levels are low, a plant’s need for fertilizer reduces. During the summer when light levels increase and the plant is actively growing, its need for fertilizer increases. As a starting point, use about one-fourth the label rate for monthly applications. If the overall plant color becomes lighter green, fertilize every two weeks.

If the new growth is dark green but the leaves are small and internodes seem longer than on the older growth, decrease the fertilizer rate. Varying fertilizer formulations are available to the indoor gardener. Many fertilizers come in specially designed formulas for indoor plants. Generally, they contain a lower percentage of the required mineral elements to prevent over-fertilization problems. Soil/Growing Medium The growing medium provides anchorage, water, and minerals. When repotting plants, make sure that the new mix is well drained and aerated, holds water and nutrients well, and is within the right pH range (5.0-6.5). A good potting mix provides ample amounts of oxygen to the root system. Most professional mixes are good to use. Some plants require special mixes, e.g., bromeliads, orchids, and African violets. Either purchase these mixes or prepare your own. Below are some formulas that can be used to prepare a homemade potting mix.

Growing Mix for Flowering House Plants The following potting mix will grow acceptable flowering plants in most homes for most gardeners: 1 part garden loam or potting soil 1 part sand or perlite or vermiculite 1 part peat moss Add 2 to 3 ounces of 20 percent superphosphate and ¾ ounce of either bonemeal or dolomitic limestone (by weight) to 4 gallons of potting mix. After sterilizing the soil (see “How to Sterilize Soil”), add 3 tablespoons of a 6-6-6 or similarly balanced fertilizer to every 4 gallons (½ bushel) of mix. Add a minor element formulation according to the manufacturer’s recommendations. Growing Mixes for Foliage Plants Although most foliage plants will grow satisfactorily in the growing mix recommended for flowering house plants, they will grow better if the mix contains a higher percentage of organic matter. 1 part garden loam or potting soil 1 part sand or 2 parts peat moss OR 1 part pine bark 1 part peat moss Add 2 to 3 ounces (dry weight) of dolomitic limestone to 4 gallons (½ bushel) of mix.

For fluoride-sensitive plants, adjust the pH so it is no lower than pH 6.5. Superphosphate contains enough fluoride to cause foliar burn on sensitive plants. After sterilizing the soil, add 3 tablespoons of a 6-6-6 or another fertilizer such as 5-10-5 to each ½ bushel. Plastic-coated fertilizers also can be used; most of them require about 2 ounces per ½ bushel. Add a minor element formulation to the potting mix per the manufacturer’s recommendation. Growing Mixes for Bromeliads Bromeliads are plants from Central and South America, which are either epiphytic (they grow on tree branches or in the crotches of trees) or terrestrial (they grow in the ground). Although most of the bromeliads can be grown successfully in foliage plant mixes, most grow better in specially designed soil mixes. Any mix for bromeliads must be well aerated and drained. 2 parts peat moss 1 part pine bark 1 part cypress shavings Add 2 ounces of dolomitic limestone to 4 gallons (½ bushel) of soil mix and a minor element mix.

Dissolve 1 ounce of 10-10-10 water-soluble fertilizer in 3 gallons of water. Use this solution after repotting and again monthly when watering. Also, add enough water to fill the vase formed by the overlapping leaf bases. Growing Mixes for Orchids Orchids have a great deal in common with bromeliads because they also grow on trees as epiphytes and on the ground as terrestrials. A mix for orchids should have excellent drainage and aeration, too. Some soil mixes that can be used are: 3 parts osmunda tree fern fiber (moisten before use by soaking in water for 12 hours) 1 part redwood bark 5 parts fir bark 1 part perlite Tree fern slabs may also be used to grow epiphytic orchids.Add 1 ounce (dry weight) of dolomitic limestone per 4 gallons (½ bushel) of soil mix. Do not add fertilizer to the mix.

After the plants are potted, add ¼ ounce of liquid 10-10-10 with minor elements per gallon of water and fertilize once every 6 weeks (if the plants are growing in osmunda fern fibers). If plants are growing in fir bark, use a liquid 30-10-10 with minor elements every 6 weeks instead of a 10-10-10 fertilizer. Growing Mix for Succulents and Cacti Cacti and other succulents grow best in a well-drained and aerated soil. 2 parts garden loam or potting soil 2 parts sand 2 parts peat 1 part perlite (crushed charcoal can be substituted) Add 2 ounces (dry weight) of dolomitic limestone to 4 gallons (½ bushel) of soil mix, 2 ounces (by weight) of bonemeal, and ½ ounce of superphosphate. After sterilizing the soil, add a minor element supplement according to the manufacturer’s recommendation. Growing Mix for Ferns Ferns grow well in most recommended mixes that have a high proportion of organic matter with good soil aeration and drainage characteristics. Use any of the suggested foliage plant mixes.

However, most ferns kept indoors grow better in the following mix: 1 part garden loam or potting soil 1 part peat moss 1 part pine bark 1 part coarse sand Add 2 ounces (dry weight) of dolomitic limestone to each ½ bushel (4 gallons) of soil mix and ½ ounce of either bonemeal or 20 percent superphosphate. After pasteurizing the soil mix, add minor elements to the mix. Add 1 tablespoon of a 6-6-6 or similarly balanced fertilizer to each ½ bushel of soil mix. Growing Mix for African Violets Any number of soil mixes for African violets exist, and most of them will grow high quality plants. A good mix should be well drained and aerated. 2 parts peat moss 1 part vermiculite 1 part perlite Add 2½ tablespoons of dolomite and 1½ tablespoons of 20 percent superphosphate to each ½ bushel of soil mix. Add 3 tablespoons of a high phosphorous fertilizer such as 5-10-5 or a similar ratio of fertilizer.

How to Sterilize Soil Sterilization reduces the number of diseased organisms and weeds present in the soil. First, mix the soil with an equal portion of vermiculite or peat moss (otherwise, the soil will become very hard). Next, moisten the mixture and place it in the oven. Allow it to “bake” at 180 degrees F–200 degrees F for 1 hour. Once the soil cools, it is ready to use. To treat soil in the microwave, first mix the portion with an equal amount of vermiculite or peat moss and moisten. Place the mixture in a plastic bag. Next, consult the manufacturer’s manual to determine the amount of time and power level needed to heat the quantity of soil to about 180 degrees F (most portions of soil will generally require about 10 to 15 minutes). Insert a probe into the soil and make sure it has heated to 180 degrees F – 200 degrees F. Allow the soil to cool before using it or storing it for future use. Make sure that the soil or potting mix you want to sterilize does not contain perlite.

At high temperatures, toxic levels of fluoride may be released and subsequently damage your plants. Acclimatization Figure 6. The two sides of acclimatization — the above-ground (light acclimatization) involves adaptation to low light, which means less growth and less need for nutrients. The below-ground (soil acclimatization) involves reduction of nutrients and water. Acclimatization is the adaptation of a plant to a new environment, and it is very important for the health and growth of indoor plants. In greenhouses, plants are accustomed to high light, nutrition, water supply, temperatures, and relative humidity — conditions ideal for fast growth (Figure 6). Residential homes, with low-light interiors and low relative humidity, will most likely produce a stressful experience for plants — the greater the difference between the previous environment and the environment of the house, the greater the stress the plant endures. Acclimatization is generally done in the greenhouse or the nursery. Plants are grown for a period of time under low-light levels and with fewer nutrients. Because this slows down plant growth, acclimatized plants are not ready for the market as early as nonacclimatized plants.

Acclimatized plants cost more compared to nonacclimatized plants, but this is money well spent. Figure 7 and Table 2 describe the symptoms and appearance of acclimatized plants. Figure 7. Acclimatized Weeping Fig; notice the large, dark green leaves and the elongated internodes. To acclimatize plants at home, place newly purchased plants in bright areas for at least 3 to 4 weeks and then move them to their final location. Porches and patios are ideal bright places for your plants in the warm months, as long as the plants are not in direct sunlight. The most common symptom occurring in plants placed indoors is defoliation. As long as it is not extensive and it slows down after a few weeks, the plants will adjust to the particular location. Keep in mind, however, that each time the plant is moved around, it will experience an acclimatization period, and such changes may become evident. Learn as much as possible about the extent of acclimatization of the chosen plants. The retailer should be able to provide this information. When shopping for plants at a garden center, ask if the plants have been acclimatized.

Remember that the most important factors of indoor plant growth are adequate light, fertilizer, and water at reduced rates. Table 2. Symptoms of acclimatized plants vs. nonacclimatized plants Acclimatized Plants What to Look for When Shopping for Indoor Plants Figure 8. Healthy roots are typically white without any discolorations. Purchase only healthy looking plants with medium to dark green foliage (unless foliage is supposed to be a different color). Avoid plants with unnaturally spotted, yellow, or brown leaves. If the plant is unhealthy at the nursery, chances are that it will die soon after consumer purchase. Look for pests on the undersides of leaves. Remove the plant from the pot and examine the root system. Healthy roots generally are and should be visible along the outside of the soil ball and should have an earthy smell (Figure 8). Any discolorations, generally brown or blackened roots, are signs of problems. Some plants, such as Dracaenas, have roots with colors other than white. Unhealthy roots also may smell foul. If shopping for ferns, do not be alarmed if you see brown-colored spots or long rows of structures on the lower leaf surface; these “spots” are reproductive structures called spores.

Selecting Containers Planters can enhance the decorative value of the plants. Consider the following when selecting a planter: Suitability for the plant’s needs Suitability for the needs of the individual and the environment Cost and availability Drainage Weight The style, shape, and size of the container should complement the plants grown. Small containers are best for small slow-growing plants, while fast-growing plants are better suited for large containers. Containers can be made from a wide range of materials — terra cotta, clay, plastic, or ceramic. Terra cotta pots, made of fired clay, are some of the most popular choices, with designs ranging from plain to ornate. Plants perform very well in terra cotta pots, as the porous surface allows good air exchange between the plant roots and the environment. Other clay containers (not considered terra cotta) range from gray to brown in color, depending on the clay used. Clay pots can be glazed or unglazed. The glazed pots restrict air exchange but offer more design choices. Unglazed pots evaporate water faster and plants in them may need more frequent watering. Disadvantages of clay containers include their weight (especially large pots) and the chance they will chip or break.

Constructed of materials such as polyethylene, polyurethane, recycled plastic, and fiberglass, plastic pots have evolved from very simple to quite elaborate. They have the advantage of being lightweight as well as chip- and break-resistant. Air exchange and water evaporation rates are generally lower in plastic containers compared with clay containers. Plants in plastic pots will not dry out as quickly as plants in clay pots, increasing the danger of over-watering. In general, there are two types of containers — ones with drainage holes and ones without. Do not allow plants in containers with drainage holes to sit in saucers filled with water, unless the plant is suspended above the water level by a layer of rocks. To avoid salt buildup, leach the soil once a month by applying a gallon of water to every cubic foot of potting medium; after a few hours, follow with ½ gallon of water. If the potting medium contains garden soil, apply 5 gallons of water per every cubic foot of growing medium. Containers without drainage holes work well for plants such as the Peace Lily (Spathiphyllum), which needs plenty of water, but they should not be used for cacti and succulents.

Pruning, Grooming, Cleaning, and Repotting When is the best time to prune? “When the knife is sharp” goes the old saying, and it means using the natural life cycles as a guide. For example, when the plant is growing rapidly and you want to maintain a certain size, prune lightly and frequently, removing shoots or shoot tips when they are small. When removing the very immature tips, the practice is known as pinching. Pinching and light pruning also increase branching of the stem and result in a stockier, fuller plant. When the plant has outgrown its container, root pruning is advisable. Pull roots away from the root mass then cut them back to within 1 inch of the soil mass. An alternative method is to make three or four vertical cuts 1 inch deep in the soil ball on the opposite sides of the root ball. If you are re-using containers, make sure that they are clean by washing out any old compost, chemical, or paint residues. Sterilize the container by placing it in a 10 percent bleach solution and rinse well. A clean plant is a healthy plant. Water flow causes salt accumulation along the leaf margins and/or tips, creating necrotic areas.

Dust dulls normal leaf coloration, lessening plant value, but it also shades plant surfaces, reflecting light that can be used in photosynthesis. Dust on lower leaf surfaces may clog stomata (specialized cells involved in water transpiration), inhibiting gas exchange within the leaf. Leaves with thick, shiny cuticles (Croton, Ficus, Peace Lily, Bromeliads) should be cleaned with a damp sponge. Figure 9. Properly repotted plant. If the plant is small, dip the foliage in tepid water and swirl it around. Water should not be used when cleaning cacti, African violet leaves, and other plants with hairy leaves. Instead, use a clean, small paintbrush brush to remove dust. Remove dead flowers and leaves regularly. Leaves with tip and/or marginal necrosis, such as fluoride damage, should be trimmed to the healthy part. If the plant has been growing well, it will likely need repotting. The decision to repot should be based on plant appearance—if it is top-heavy, if it fills the container with new shoots, or if it has extensive root growth out of the pot’s drainage holes. Ideally, plants should be repotted in 1 inch increments.

Planting into too large a container will give the roots more soil than they initially need. The excess soil will hold extra moisture, creating overly wet conditions. Increase pot size through smaller increments rather than doubling the pot size in one step (Figure 9). Pest Management Figure 10. Various scales. Very few plants stay pest-free forever. Pest insects are more likely to be encountered on indoor plants than diseases because the interior environment rarely offers favorable conditions for foliar diseases to develop. However, when plants are grown under stressful conditions (such as low light and excess water), soil-borne pathogens often develop. Figure 11. Various scales. Scales are ⅛ inch to ⅓ inch long with various colors, depending upon the species. The three main families of scales are armored (the body covering can be separated from the body), soft (the body covering cannot be separated from the body), and mealybugs. Scales suck plant juices from leaves and stems, causing stunting, leaf discoloration, and death of the tissue. As a result of their feeding, sticky “honeydew” (digested plant sap) is excreted (the exception is armored scales).

Honeydew offers a growing medium for a fungus called sooty mold, which, when present, can detract from the plant appearance and block light from reaching the leaf surface. Scales are usually inconspicuous; by the time infestation is noticed, the population is usually very large (Figure 10 and Figure 11). Mealybugs are soft bodied, 1/5 inch to 1/3 inch long, and covered by white, waxy filaments, giving them a white, cottony appearance. Insects are frequently found on the new growth at the stem apex, where they suck plant juices, causing leaf wilting and abscission (Figure 12). Some species of mealybugs appear first on the undersides of leaves. Mealybugs excrete sticky honeydew, which attracts sooty mold. Figure 12. Mealybugs are the major pest problem for houseplants. Figure 13. Aphids. Aphids are soft bodied, pear shaped, 1/25 inch to 1/8 inch long, and are usually green in color (but may be pink, blue, brown, yellow, or black).

Aphids reside on new growth or on the underside of young leaves, where they suck plant juices, causing deformed, curled growth of new leaves, buds, and flowers. Aphids also excrete honeydew. Aphids are usually wingless but develop winged forms when colonies become too large (Figure 13). Spider mites are the second most common pest problem on houseplants (Figure 14). The adult females are about 1/50 inch long, hardly visible with the unaided eye. Mites feed on the undersides of young leaves. Infected areas are grayish or yellow speckled. Webs form as a means of dispersal. Spider mites thrive in hot and dry conditions. Figure 14. Spider mites with webbing. Figure 15. Thrips. Thrips, while uncommon on houseplants, predominantly feed on plants in patios and other outdoor areas (Figure 15). Thrips are small, slender, 1/25 inch to 1/12 inch long, and tan, black, or brown in color, with lighter markings. Adults and larvae feed on shoot tips, flowers, and leaves by sucking sap and cell contents.

Injured tissue has a whitish or silver-flecked appearance due to the light reflecting from the empty cell walls of the dead cells. What to Do for Plant Problems Pests The best method is prevention — purchase pest-free plants. Remove a light infestation of mealybugs or aphids with a cotton swab dipped in rubbing alcohol. If outdoor conditions permit, take the affected houseplant outside in a protected area, where natural predators will eventually come and rid the plant of the pest. Treat with insecticidal soap. The best results occur on plants that have been hardened off in the interior environment. New plants, if they have not been acclimatized (accustomed to lower light, fertilizer, and water levels), are going to be tender and should be treated after the first couple of weeks. Add 2 teaspoons of insecticidal soap per gallon of water and wipe foliage and stems with the soapy water and soft cloth. Heavy infestations may be too extensive to treat. Discard these plants and do not place them in your compost pile. Do not introduce beneficial insects indoors! They may work great in the greenhouse with a large number of plants and pests, but there is just not enough food in your home to sustain their population.

Most pests can be controlled culturally on indoor plants without the use of chemicals. Another potential problem in the indoor garden is the occurrence of various diseases. For a disease to happen, three factors must be present: (1) a susceptible plant, (2) a viable pathogen, and (3) a favorable environment. Because the home has very low relative humidity and water is often applied directly to the growing medium (thus keeping the foliage dry), chances of a foliar disease occurring are minimal. Leaf spots are the most common problem, but they are usually not caused by a disease. For example, leaf scalds occur when water droplets on the leaves act as lenses and focus excessive light in one spot, bleaching the chlorophyll and killing the underlying tissue. Spots with patterns are signs of a disease, including a tan center, dark borders, and/or light-colored borders called “halos.” Dark structures may be present on the underside; these contain a means of dispersal called spores. Figure 16. Bacterial diseases cause spots, soft spots, and wilts. The signs of a fungal disease are sooty molds, rusts, mildews, rots, cankers, spots, and wilts.

Viral diseases cause mottling, distortion, and dwarfing. Most importantly, avoid causing stress to plants. A healthy plant is much more likely to fight off a disease than a stressed one. Use a simplified key for identifying the causal agent for a disease (Figure 16). Soil-borne pathogens are commonly found on stressed plants. Soil-borne pathogens affect plants at or below the soil line; disease development is usually well underway before symptoms are noted on plant parts aboveground. Soil-borne diseases commonly occur when the growing medium is kept excessively moist and fertility levels are high. Low light and over-watering create favorable environments for soil-borne diseases indoors. The most common causes of stress in interiors are low light and over-watering. Summary of Cultural Care Table 3 provides a listing of more than 200 plants and their cultural requirements. To summarize cultural care guidelines, the following abbreviations and coding numbers are used. These guidelines apply to actively growing indoor plants.

L = Light Sunny light areas: At least 4 hours of direct sun High-light areas: Over 200 ft-c, but not direct sun Medium-light areas: 75 ft-c to 200 ft-c Low-light areas: 25 ft-c to 75 ft-c T = Temperature Cool: 50°F night, 65°F day temperatures Average: 65°F night, 75°F day temperatures Warm: 70°F night, 85°F day temperatures H = Relative Humidity How to Select the Best Grow Light for Indoor Growing - Urban Organic Gardener How to Select the Best Grow Light for Indoor Growing Posted on Feb 10 2012 - 1:04am by Mike Lieberman Not all light is the same. Plants respond differently to different colors of light. Light on either end of the spectrum, blue light or red light, have the greatest impact on photosynthesis. Kinds of Light Blue light, referred to as cool light, encourages compact bushy growth. Red light, on the opposite end of the spectrum, triggers a hormone response which creates blooms.

Grow lights producing the orange and reddish light typically produce substantial heat, however, some lights are able to produce full spectrum light without the heat. Grow lights come in all shapes, sizes and price ranges. As a general rule, inexpensive lights to purchase tend to be the most expensive to operate and the least effective. While price is not necessarily an indicator of performance, many of the efficient grow lights require ballasts as well as specialized fixtures. Image of vegetable being grown indoors under artificial light is via fortikur.com. Check out SeedsNow.com if you’re looking to grow organic vegetable and herbs from seed. Click here to read more about what GMOs are. It’s really easy for you to grow all kinds of vegetables, herbs, and sprouts inside. All year long! Invest in a grow light and you’ll be happy. Basic Types of Grow Lights These lights run the gamut of performance and price range. Incandescent Lights. The least expensive lights to purchase cost around $30. These incandescent lights work well for specific plants where the light is placed a minimum of 24” from the plant. These lights get extremely hot so they must be used with care.

Spot grow bulbs, color corrected incandescent lights, install easily and are good for use with a specific plant or a small grouping of plants. Most spot incandescent bulbs last less than 1,000 hours. Some light fixtures come with a clip handle so you can put them exactly where they’re needed. Fluorescent Grow Lights. They are a common choice for homeowners. Fluorescent lights are reasonably energy efficient and relatively easy to install. A typical fluorescent bulb will last approximately 20,000 hours. Fluorescent light is typically on the blue end of the spectrum. Blue light encourages bushy compact growth which makes them perfect for seed starting. Blue light is also cool to the touch making it possible to place lights within just a few inches of the seedlings. New Full-Spectrum Fluorescent Lights. Provide the red spectrum as well to encourage blooming. Combining the lights in a fixture makes for even, all around growth. The next generation in fluorescent lighting includes the new T-5 lights. These new lights have extremely high output but are energy efficient and long lasting. The T-5 lights triple the light output of normal fluorescent lights without increasing the wattage.

Plants absorb a high percentage of T-5 lighting because the fixtures function well very close to plants. High output bulbs require a high output fixture to operate, so the bulbs and normal fluorescent fixtures will not work together. LED Lights The newest type of grow lights use LED technology. One major advantage to the LED lights is the small size. LED lights are only a few inches in diameter and are easy to mount. In some greenhouses, LED lights may be the only practical light option. Hanging most grow lights requires a strong greenhouse structure and a place to hang the lights. LED lights weigh a fraction of other lights and are easy to configure where needed. According to LED manufacturers, LED grow lights maximize blue and red light to provide and excellent balance for plants. They do not have much green-yellow light. Since humans see green-yellow light best LED grow lights appear dim to our eyes. This is an exciting new technology that will be interesting to watch as it develops. The Best Grow Light Option Now that I’ve given you a good rundown on greenhouse lighting options, it’s also important to mention darkness. Almost all plants benefit from a period of six hours or more of darkness.

It’s a good idea to know how much light your plants need, but unlike commercial growers, hobbyists often have a wide variety of plants so they need to take a broad approach to lighting. Fluorescent lights offer excellent overall lighting options. Other Considerations If you chose to use any type of fluorescent lighting, you will need to account for plant growth. Fluorescent lights perform best when positioned very close to plants. As plants grow into the light, it is important to raise the fixture. Generally only the plants touching the lights will burn, but be prepared because they grow quickly. Adjustable hangers are a good solution. These hangers move easily allowing you to make quick adjustments. If you’re looking for non-gmo seeds that grow well using hydroponic systems, click here . Your Turn Are you currently using grow lights to grow indoors? What kind? What are you growing? Do you plan on growing indoors using grow lights? Let me know in the comments below. Michelle A. Great lighting tips. We want to bring our garden indoors and this will help. We have a tiny greenhouse attached to our home which gets lots of good natural light during the year, but when the weather turns we’ll need better lighting. Thanks!

😉 Mike Lieberman Glad you found it useful! Susan Thank you for the very helpful post! Tris Cool post, Mike! The hubby and I are really interested in the LED lights right now. We’ve already switched to LED Christmas lights for the tree and have several LED flashlights that you hand crank…no batteries! Looks like this is the next step for our seedlings and houseplants. Right now, I have cool blue flourescents in shop style fixtures for the houseplants and keep them on a timer. It works ok but we have to hang on to the burnt out ones until there is a recycling event near us because you can’t just toss those in the trash. Big no no! Mike Lieberman Glad you found it useful. Mike Lieberman Sounds like you are on your way and doing a great job! Sandra Whitlock Dwan I have what I think are fluorescent bulbs installed under my cabinets in my kitchen to provide extra light to the counter workspace ~ the long tube like bulbs. Would it be OK to use those? And could I install full-spectrum fluorescent bulbs in them?

I also am slowly changing my CFL’s to LED’s in the house and have some in my kitchen so would the plants benefit from them or are the LED’s used for plants a specific kind of LED? What makes it a “grow light” vs. just a normal light bulb you might use in your home? Thanks! Angela at Frugal Gardening Great ideas. However, I find creating my own grow lights units very rewarding. ScottfromtheBK I set up a grow light system last year and will definitely be using it again this year. I have a fluorescent system (with T-5s) that I found online; the fixture and bulbs were a little pricey, but I searched around and found a better deal from a lighting distributor than from any of the gardening sites. I figured that a little more investment up front would save me in the long run. The system is set up in the top of a bookshelf because I don’t have much space in my NYC apartment for a dedicated seed-starting area. I screwed some hooks into the underside of the top of the bookshelf, took out a shelf, and hung the grow light from the hooks.

I bought a cheap light timer and set the time increment to 18 hours; with the timer I don’t have to worry about remembering to turn the lights off and on (because I would definitely forget). I also have a capillary mat that I set my seedlings on so I don’t have to worry about watering either. Overall, I think my lazy-man’s system works pretty well. I’ll try to post a picture when I get some seeds up and going… Mike Lieberman That’s great. Mike Lieberman Sounds dope. Gonna be putting some stuff together myself. Def share the pics when you get started. Mike Lieberman Thanks for the question Sandra. I am not a grow light specialist and have asked someone at The Greenhouse Catalog to chime in with a response. Kathy Sandra, you should be able to replace your standard fluorescent bulbs with full-spectrum grow lights as long as you make sure they are the same size as the bulbs you currently have in your fixture (most commonly T12). If you grow under your kitchen cabinet, I recommend that you make a platform for your plants/seedlings to sit on, so the top leaves are just a few inches below the fixture.

You will need to adjust the platform as the plants grow. Your home’s LED lights are designed for visual appeal (a limited spectrum of light) and not for growing. LED’s designed as grow lights have full-spectrum light with a lot of reds and blues for plant growth, but they are not visually appealing as a house light. ScottfromtheBK Here are pics of my setup. Pretty self explanatory, but let me know if there are any questions. I planted the seeds in coir in the biodegradeable tray which sits on a capillary mat with a water reservoir below. The coir is working out awesome – I definitely recommend it as seed-starting medium. In this tray I have (from left to right): genevese basil, citrus basil, mini bell peppers, cilantro (the empty row was cilantro too… I wonder if I just forgot that row… d’oh!), and cherry tomatoes. Hit me up if you have any questions. Mike Lieberman Nice bro. Good isht! Andre Ferchau I’ve worked with LEDs since they were invented (about 1975). What people don’t realize is they are not at all like any other light source except, and only barely like, fluorescent.

They and fluorescents and HIDs output less than a full spectrum. So no matter what you read about full spectrum only exists in the incandescent bulbs and ideally the halogen bulb. Why? The Sun is what we define as full spectrum. It has ‘all the colors’ of the rainbow. No light but halogens (and to a limited extent any incandescent) bulb has this same full spectrum. OK but so what? Have you ever used induction lighting Amie Hello! We plan to grow indoors come frosty weather… part of our food source comes form the food t that I grow. I do can and preserve what i know how to do …..canned is good, dehydrated is good……but fresh is best. We want to start aquaponics in our garage……and use the space around the tanks as a growing in house, (all in the garage). Any suggestions on how many lights? our garage is 14X10……. and we open it everyday for fresh air and what not ~that the plants need. i have to self pollinate which is timely…or “time consuming’…. but IF the lights are good and don’t cost a fortune……thats the wat for our winters.

`please advise. amoja Help me. I have a LOT of rather gigantic houseplants, lit mainly by costly CFL’s. I have been looking to replace them with blue, red & cool white LED light bulbs. Or perhaps some LED string lights. I understand (I think) that a white LED needs to be 450 lumens, but I need to know how many lumens a blue LED bulb needs to be effective. Or a red one. I need about 30 white bulbs, 4 or 5 red ones, & maybe 8 to 10 blue ones. I think. Not a lot of $ going on here, so I’m looking for an inexpensive source. Plain, screw-into-lamp socket bulbs. Any suggestions will be much appreciated. Namaste’. chickenscratch Only thing I can say is stay away from The Greenhouse Catalog I ordered some lights from them and they did not work- DOA. No refund or replacement offered or anything. They tried to claim I was using them wrong. Come on, really? chickenscratch Seriously though, this article is riddled with cheap plugs.

devideaster Proper lighting is the most important factor that should be considered at the time of growing any types of plant. I am really impressed by the way you have explained about best grow light options. Michelle Hi my name is Michelle and i was trying to get my own garden started indoor. I needed a few tips on lighting Michelle Even wanting to grow fruits and vegetables will i have to use a certain type of lighting? David Have you tried the lights from Illumitex? They’ve got some incredible plant growth science behind their LED grow lights. Aarielle Aaers Wow, great comment, really appreciated it. Thanks! I love Halogens. Although the bulb is more expensive, the light is most beautiful. And, we use 12V so they’re very inexpensive. : ) Hydroponic Lights Can we decorate our home easily with using grow light ??? iris In fact, for growing your plants, the lamp must be with red and blue led, and you need to know your indoor garden area, then you can chose the right lamp for your room.

iris this lamp was use to promot plants grow quick,dear friend Danny im using t5 lights in an industrial sized hydroponics system, but do different seeds need different hights to germanate plus do they need different lux levels, please help just starting out and dont want to get it wrong Stephen Wadding Quality information has been shared by you. If you are bit confuse to choose which is a better grow light then read this stuff and be sure about it. I think LED lights are best grow lights. Loulou My experience with halogen is they release a lot of heat< I have just converted to LED, need a few weeks to see how it work. Tom Thanks for a clear explantion of grow lights it is the best and clearest i have seen and I will not have to spend a ton of money to start our seeds. Rob Thank you for the info. I just planted some organic seeds into little cells, and currently have an incandescent light on them, but Im going to put a fluorescent light on them now that I’ve read your article.

The packages say to start indoors, Im growing some chilli peppers, cayenne peppers, and two types of tomatoes, and the label says to keep them warm and under a light. Is fluorescent a good choice? Do they need sunlight? And a few hours of darkness is good for them right? Puchong Vongthongdee May i used White LED for Grow Light ? because my pot is small and i want it light Color friendly for human eyes. As i know plant love blue and red. but white led are contain RGB color but they are some RGB LED also all 3 color build in 1 LED which one this the best for human eye and plant danilekk what is most important when to buy a grow light? there are two type: led panel light or led UFO, which it better? Erich Hi how many light bulbs do I need ? how do I know I have enough Light ? bill there is a new light on market called the sun engine built in ohio it is said to be the only grow light which duplicates the sun . do you know any thing about it .where can you buy them K B I’m trying to do a better job of getting my potted plants from outdoors to make it through the winter, indoors.

The lack of light is part of the problem. I can usually get most of them through, but they look so scraggly by Spring. I can group them together pretty well in one place, but they are all different sizes. After reading the advice above, I don’t think a fluorescent will work. I’m asking now so I can have everything ready when I bring them inside again this fall. cunt durrrrrrrrrrrr DirtyDarlene I want to try growing veggies indoors this winter. I have an all glass south facing sunroom. It currently has an awning-like covering over the top which I can roll back for optimal sunlight. It has windows about 3-4ft from floor that crank out. It has two ceiling fans. It has a heat or air unit inside it. I have been trying to study the best options for me to get setup. I get so many different opinions that I am still unsure. I have a plan for the stands. Could you offer your opinion for my winter garden? I enjoy a very nice organic garden through the summer months.

bill blizzard can i grow ginseng and golden seal root inside with grow light system,if so please give me some instructions and what i need to get started Lana Critchfield Barton I picked up an incandescent plant light bulb today for a plant that is struggling in a northeast window. It’s all my little local store had. Is this bulb enough or do you recommend a florescent bulb when I’m able to get to a bigger town. I live very rural so I can’t always get the best right away. peteski72 I’m trying to reduce my cost while growing indoors. The major expense is electricity. I went all out in he begging and bought a 600 w MH and HPS light. All was well, even sucking up the cost, eventually it became to much to bare. Now I am all over the map trying to come up with one light or to use a combination of lights I have and possible adding a LED. I have a 4 tube HO fluorescent ballast. I have four tubes for Vegetation and four for the flowering stages.

Also, I have numerous CFL’s 55w equivalent 200w replacement I see LED’s are getting better and the price is dropping along the way. What I don’t know is; is a $250 168 w x3 sufficient? I have a very small area in which I can utilize it’s basically a 4 sq.ft area. It is a small operation and intended to be for the time being. It is crazy to be spending $100 to $150 a month. I am open to any/all suggestions. I need clarity before I proceed. Tank you so much for your time and attention to my matter. Peter Cindy what lights are ok for wheatgrass? Cindy How long do i leave the light on for wheatgrass? Ted K What kind of lights I need to grow tomato plants in side michael92064 Investigating LED grow lights. Some have LEDs of different colors arranged together and some have LEDs all the same (whiteish) I just want a cost effective solution to starting my vegetables early before planting outside. Bill Flynn HELLO, I AM NEW TO GREENHOUSE GARDENING, I LIVE IN NYC .

THE GREENHOUSE (SHED TYPE) IS 80 SQ/FT FOOTPRINT. I PLAN TO GROW PRIMARILY TOMATOES, VARIOUS HERBS AND GARDEN FLOWERS. I AM PREPARING TO GET SEEDS STARTED AND WILL DO SO IN THE BASEMENT. AFTER READING YOUR INFO HERE, I WOULD GUESS I COULD START WITH A 4′ T5 SETUP. I WAS PLANNING A 2 TRAY ATTEMPT AT GROWING SEEDLINGS ( TO TRANSPLANT TO G/H IN MARCH/APRIL? WOULD YOU ALSO SAY A HEATING MAT IS A GOOD IDEA? I AM INTERESTED IN ANY TIPS SHARED….THANK YOU. Steve where to I find the GMO seeds? Sherri Lucas-Gibson Google gardening in small spaces.. Aquaponics is a great addition to a greenhouse Sherri Lucas-Gibson It depends on the money you want to spend, room size and plants you want to harvest.. I do indoor and outdoor both veggies and medicinal marijuana.. It is all about light spectrum.. Plants see a different light than we do.. And they don’t see green at all..

That is the colour bounced off of them.. That is why we see them as green.. Because of that light refraction we have no real idea of a plants true colour Sherri Lucas-Gibson You can’t miss with full spectrum.. If there is no blossoming needed.. A blue spectrum sounds better.. Red is for blossoming Bill Flynn Thanks for taking the time to reply……mine is a small greenhouse 80 sq/ft in NYC outer boro……will check out Google. Happy planting! Bill Alex Storey You can, But you do realize that ginseng can take up to 6 years to grow right? Jeff Hello, considering switching to LED lighting. would a 90 watt LED light used for lighting up a public parking garage put out the same blue and red spectrum the plant LED lights put out? Laura in Ohio Strangely enough I want to grow dandelions and other weeds (all year) for my tortoises to eat. I live near Cincinnati, Ohio so summers are hot and winters are very cold (and snowy) … I inherited a small garden set up of 4 shelves with a plastic cover that goes over it …. So, it could be inside or outside (weather permitting) ..

but with “shelves” how could a ” on the top” light shine down on all shelves? Are there side lights or some way to give all the shelves grow lights? Laura You could hang a light on the underside of each shelf (except the bottom) with adjustable hangers (a lot of people use chains) and put the plants on the shelf below. I don’t think that using just one light will get the job done. I have also seen the plastic covering the greenhouse lined with tinfoil or mylar (something reflective) to reflect extra light back on the plants Niko Hey! I’m moving into a small room Boston soon with NO windows to the outside. I’m considering having a few hanging plants that live in low light, like English Ivy and Boston Ferns. What would be ideal lighting for me, if anyone can help? Im trying to figure out what bulb to use and I only have a 1.5′ square (width and length) by 6′ (height) space open for plants. fernis I will like to move the bananas plants to the basement, for the winter time.What kind of light would be for this plants?

Nicolle Toth-Braunberger My place is floor to ceiling windows and a new condo building is going up next door. The amount of sun will be almost nil in about a month – are there bulbs that I can use in my existing fixtures that can help my plants stay healthy? Thank you! I’m starting to panic. Jennifer I have a large Ficus Tree, a spider plant, and two different kinds of peace lilies. Oh and a huge Mother-in-law tounge. My natural lite in my living room is awful. I have put up a 18″ under counter florescent lite above my plants. They always start looking bad by the time I can move them back to the porch. Should this help them or do I need to buy a special bulb. I always worry about my Ficus. I’ve had it for about 18 years. It was two feet tall when I got it and it is now almost six feet tall. It went crazy this summer and got bushier. I don’t want it to start doing poorly. John Butler Can you mix lights… I have florescent now, I have LEDs ordered…. can I use both in same room.. Bob

Question: What kind of plants grow where they are not wanted?
Answer: weeds