perennials distressed or dying

Question: A number of perennials are displaying signs of distress-stems bending down, newer leaves on tops of plants are smaller, blooms are deformed, newer buds on black-eyed Susans are brown and appear to be dead.  Affected plants include:
goldenrods, coneflowers, cardinal flower, phlox, black-eyed Susans

responder: Pat - MGV Cuyahoga County  Replied August 10, 2024, 9:28 AM EDT
response: If there are no other signs of pest or disease damage, the plants are probably suffering from heat stress. Plants are sensitive to both air and soil surface temperatures. Temperatures ranging from 60° to 85°F are optimum for plant growth and development.   Plants have limited ability to regulate temperature and begin to experience stress as air temperatures rise above 86°F.   Water evaporation through pores in the leaves is the primary cooling mechanism used by plants. If a plant doesn’t have enough water, the pores in the leaves close and the plant can no longer keep itself cool. When temperatures are exceptionally high and prolonged, plants can lose water through evaporation much faster than the roots can absorb it.  Wilted, drooping leaves, resulting from a combination of excess water loss and high internal temperatures, are often the first signs of heat stress.   Sunburn is another type of heat damage caused by excessive exposure to direct sunlight. Sunburned leaves and stems become discolored and appear scorched.  Plants experiencing continued heat stress will be unable to maintain the processes necessary for growth and development and will become stunted and vulnerable to insect attack.  So what can be done to minimize effects of heat stress:  Water thoroughly in the morning on days when high temperatures are expected, to help plants cope with excess heat. In general, when watering plants, do it deeply and infrequently so that they put their energy into sending roots down into the lower depths of the soil. During a period of drought, the roots are then able to access moisture reserves deeper in the soil.  If plants are watered too lightly, then the moisture only penetrates the top layer of soil, resulting in plants with shallow root systems.  During a heatwave, the water in the top inch of soil quickly evaporates, so heat-stressed plants also need deep watering.If discovered in time during a heat wave, a drooping wilted plant can often be revived with additional water.   Watch for radiant heat - Pay special attention to plants next to walkways, patios, and other structures that radiate heat. They may be the first to show signs of heat stress and the need for extra water.  Add mulch - Apply two to four inches of organic mulch over the root areas around garden plants, trees, and shrubs. This will lower soil temperature and diminish moisture loss.  Provide shade - Use shade cloth to provide direct sun protection and reduce the air temperature around sun and heat-exposed plants.   Avoid applying fertilizers during extreme heat as they stimulate growth and add to plant stress. Fertilizers also absorb moisture from the root zone.  Many plants will stop blooming during extreme heat. Removing the spent flowers can improve the plant's appearance, keep plants from spending precious resources on fruit and seed development, and set the plant up to bloom again once the heat wave passes.  Following is a link to Iowa State Univ Extension with more info about managing the garden in a heat wave: https://yardandgarden.extension.iastate.edu/how-to/managing-garden-extreme-heat

responder: The Question Asker Replied August 10, 2024, 11:55 AM EDT
response: Thanks for your prompt response. I'm sorry I provided you with very skimpy information.  These plants and the damage are confined to one area; other areas of unaffected so far.  We do follow the watering tips and do not fertilize the native pollinators.  Does this point to a fungal disease?  How can I identify whether or not it is a fungal disease?  If it is, what are the treatment options?   Thank you!

responder: Pat - MGV Cuyahoga County  Replied August 10, 2024, 1:42 PM EDT
response: If you think it might be a fungal disease it would be helpful if you could send some close-up pictures of leaves that might be spotted or discolored as well as pictures of deformed flowers. The close-ups would help in identifying problem other than heat wilt. Following are a few links to University Extension sites that provide more info on common fungal diseases with pictures that may help you determine if your plants are affected. Many if not most fungal diseases show up on the leaves. https://www.extension.iastate.edu/news/yard-and-garden-common-diseases-perennials https://extension.umd.edu/resource/fungal-leaf-spot-disease-flowers/ https://extension.psu.edu/key-herbaceous-plants-and-key-pathogens-diseases

responder: The Question Asker Replied August 10, 2024, 6:54 PM EDT
response: Thank you!  This is very helpful.  I will send some photos tomorrow (Sunday).   On Sat, Aug 10, 2024 at 1:42 PM Ask Extension <<personal data hidden>> wrote:

responder: The Question Asker Replied August 12, 2024, 11:26 AM EDT
response: Attached are three photos.

responder: The Question Asker Replied August 12, 2024, 11:58 AM EDT
response: Attached are three photos showing some leaf damage.  That seemed to be the maximum I could attach.  Please let me know if it would help you if I sent additional photos. Thank you!

responder: Pat - MGV Cuyahoga County  Replied August 12, 2024, 7:37 PM EDT
response: Fungi can cause the leaf spots showing up in picture #3. Purple Coneflower (Echinacea) is susceptible to fungal leaf spots. Fungal diseases usually start with the lower leaves then move up the plant. Septoria Leaf Spot is common. Remove diseased parts of the plant, avoid overhead watering, do not over mulch and spray with a fungicide that contains one or more of the following ingredients: copper, chlorothalonil, Captan, Mancozeb, Propiconazole, Tebuconazole.   Following are a few University Extension links with more info on Purple Cone Flower diseases: https://extension.psu.edu/echinacea-diseases https://henderson.ces.ncsu.edu/2022/07/pest-alert-coneflower-issues/  The picture of the goldenrod shows browning at the tips of the leaves which is probably heat stress but goldenrod can also suffer from fungal diseases. Following is a link to Penn State Extension with info about Goldenrod diseases:  https://extension.psu.edu/goldenrod-solidago-diseases

responder: The Question Asker Replied August 13, 2024, 10:26 AM EDT
response: Thank you for this helpful information. A question about the other plants that show heat stress:  the newer leaves and flowers at the tops of the plants are stunted.  Should they be pruned back to the normal-sized leaves?  Will that encourage growth of normal leaves and flowering?

responder: Pat - MGV Cuyahoga County  Replied August 13, 2024, 10:50 AM EDT
response: Remove dead flowers, leaves and stems. Leave enough green leaves so the plant is capable of photosynthesis. Keep watered. You may or may not get new leaves or blooms this year but if the roots remain healthy, you should have a healthy plant in the spring.

responder: The Question Asker Replied August 13, 2024, 11:14 AM EDT
response: Thanks so much.  That makes sense for some plants.  There are many that are still green, with the newer growth being smaller and blooms that look deformed.  Should they be pruned back to where the leaves are a normal size?  If not pruned back, will they continue to grow and bloom as they typically would?  We are adjusting our watering to manage the heat stress that apparently has caused the problem. I appreciate your responses very much!  Thanks again!On Tue, Aug 13, 2024 at 10:50 AM Ask Extension <<personal data hidden>> wrote:

responder: Pat - MGV Cuyahoga County  Replied August 13, 2024, 1:49 PM EDT
response: If the leaves are green I would leave them even if they are smaller. I would prune deformed flowers or flower buds. There is no guarantee that they will produce normal sized leaves or flowers this season but if the roots survive, you should have a normal plant next season. If you have not fertilized recently, it wouldn't hurt.

responder: The Question Asker Replied August 13, 2024, 2:17 PM EDT
response: Thank you for answering my questions.  On Tue, Aug 13, 2024 at 1:49 PM Ask Extension <<personal data hidden>> wrote: