Rain gardens

This article is about planted installations designed to capture surface runoff in an amended soil. 
For more highly engineered systems, see Bioretention. 
Image:Rain garden.png|thumb|700 px|An image of a typical rain garden, with various vegetation, shrub species, and perennials to increase infiltration, filter out pollutants and reduce runoff/overland flow directed into the facility from rainwater collected from a building's roof. Rain gardens also provide food and shelter for pollinators, bird species, and other wildlife. More complex rain gardens with drainage systems and amended soils are often referred to as bioretention facilities. A note: The following is an "image map", feel free to explore the image with your cursor and click on highlighted labels that appear to take you to corresponding pages on the Wiki.
circle 408 129 106 Shrubs
circle 394 921 102 Shrubs 
poly 219 169 295 150 334 218 316 261 218 264 Stone
poly 211 265 211 342 245 384 282 345 332 360 371 298 414 299 445 329 499 315 523 327 524 278 468 223 411 244 346 221 319 264 Mulch
poly 138 1017 172 1073 405 1121 509 1124 617 1074 627 1016 521 1066 382 1069 Amended soil
poly 286 1100 431 1170 519 1162 618 1080 522 1123 412 1123 Sand
circle 536 215 52 Perennials
circle 591 321 51 Perennials
circle 173 213 53 Grasses
circle 154 312 55 Grasses
circle 187 399 52 Grasses
rect 108 904 256 986 Grasses
rect 216 989 307 1036 Downspout disconnection
poly 150 6 253 156 230 162 128 20 Downspout disconnection 
poly 506 905 495 963 472 997 445 1022 391 1062 517 1058 628 1007 617 928 Perennials
==Overview==
Rain gardens capture roof, lawn and driveway runoff from low to medium density residential lots. These can be simple gardens constructed by the homeowner as a retrofit, or they can be professionally designed into a residential development. 
The fundamental components of a rain garden are:
*An amended soil mix
*Suitable planting
Additional components may include:
*A splash pad of stone to prevent the downspout flow from eroding the soil
*A simple overflow swale to another area of the garden
==Planning Considerations==
Raingardens look like typical gardens. However, their infiltration and bioretention functions are much greater than normal gardens. By landscaping areas to include a surface depression of approximately 150 mm, rain gardens allow runoff from residential properties to collect and to easily absorb into the ground. Within the rain garden, special types of soil, 'filter media' or soil amendments increase the amount of water absorbed by the garden and infiltrated into native soils.
Location is very important to a functioning rain garden. When looking at potential locations, look for low areas where runoff can be easily be directed into the garden. Rain gardens are a great option for residential LID retrofits because homeowners can customize the garden to suit their desired styles. They can be planted with a variety of vegetation including shrubs, grasses and flowers.
A well-designed rain garden can be maintained with minimal care, which is a great marketing point for persuading homeowners. In the first two years, the plants will need watering to ensure they become established. After this establishment period, the garden should only need simple maintenance, e.g. weeding.
For a table summarizing information on planning considerations and site constraints see Site considerations.
==Design==
===Plant Selection===
The design of a rain garden allows for several different planting zones. 
*A variety of plant material can be selected based on the desired aesthetic, including turf grass, ornamental grasses and perennial flowers, shrubs, and trees.
*The aesthetic can range from very naturalistic to quite formal, depending on the planting plan.
*Vegetation must also be capable of tolerating prolonged wet and dry periods unless an irrigation plan is in place
*If the facility is intended to be relatively inconspicuous, then the tallest plant material should be placed into the deepest part of the rain garden. Otherwise, choose taller plants for the back of the garden tapering the height down to the front of the garden. Peel Fusion Landscaping
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Since rain gardens are typically smaller scale homeowner projects smaller stock plants may be considered. Smaller containers may be easier to purchase, transport, and plant, but it may take longer to have a fully vegetated garden. Plant material per Canadian Standards for Nursery Stock, Eighth Edition. Seed planting is not recommended for rain gardens. Plants should be container grown, balled and burlapped or wire basket. 
Below are recommended plant sizes for planting rain garden features:
 
Deciduous Shrubs - 60 - 80 cm height
Coniferous Shrubs / Broadleaf Evergreens - 40 cm spread (roughly #3 or 3 gal. container) 
Perennials/Grasses - 15 cm to #1 or 1 gal. container stock
Ground Cover/ Vines - 10 cm to #1 or 1 gal. container stock 
====Hydric Zone Criteria====
Low Zone 	Often referred to as the extended detention or shoreline fringe area. This area is frequently inundated during storm events, and is well-drained between rainfall events.
Mid Zone 	Often referred to as the flood fringe area. This zone is inundated less frequently (2 – 100 year storm events) and has periodically high levels of moisture in the soil. The ecology of this zone is a transition from the Mineral Meadow Marsh/Beach-type community to an upland community.
High Zone	Often referred to as upland area. The ecology of this zone is terrestrial due to its elevation in relation to the filter bed. The zone most closely resembles a Cultural Meadow or a Cultural Thicket community, depending on the mix of grasses, herbaceous material, shrubs and trees utilized.
[[File:Soil moisture zones levels.PNG|600px|thumb|A simplified schematic depicting the three primary zones associated with soil moisture levels and the appropriate plant species selected for each zone's specific soil characteristics, best adapted to the area's growing conditions. (Source: CVC, 2022)CVC. 2022. Native Plants for Rain-ready Landscapes> plant these native wildflowers, grasses, shrubs and groundcovers to help manage stormwater - beautifully. cvc.ca/GreenYourProperty. https://cvc.ca/wp-content/uploads/2022/03/com_lo_rain-ready-guide_20220328-FINAL3.pdf]]
Low Zone
*Mineral Meadow Marsh plant community 
*Grasses, Sedges, rushes, wildflowers, ferns and shrubs that have an ‘Obligate’ to ‘Facultative’ designation 
*Wetland ‘Obligate’ species that are flood tolerant as they will persist in average years and flourish in wetter years.
*Plants that are likely to occur in wetlands or adjacent to wetlands. 
*Plants with dense root structure and /or vegetative cover are favoured for their ability to act as pollution filters and tendency to slow water velocity
*Be advised these practices are not constructed wetlands and are designed to fully drain within 48 hours.
Mid Zone
*Plants able to survive in soils that are seasonally saturated, yet can also tolerate periodic drought. 
*Species include grasses and groundcovers, as well as low shrub species.
High Zone
*Plants should have deep roots for structure, be drought-tolerant and capable of withstanding occasional soil saturation. 
*Trees and large shrubs planted in this zone will aid in the infiltration and absorption of stormwater.
*This area can be considered a transition area into other landscape or site areas.
*A variety (min. five) species should be used to prevent a monoculture.
==Landscaping Design Consideration==
*In natural areas, a diversity of plant types not only adds beauty but also create a thick underground root matrix that keeps the entire plant community in balance. In fact, 80% of the plant mass in native prairie communities is underground. Once the rain garden has matured and your sedges, rushes and grasses have established a deep, thick root system, there will be less change in species location from year to year, and weeds will naturally decline. Appendix D - Low Impact Development Concepts, Rain Gardens: A how-to manual for homeowners, Wisconsin Department of Natural Resources, Page 15.
 
*Smooth out any sharp corners to create flow in your garden. 
*Neat edges can be established using pavers, walls or bands of turf create an attractive amenity within the residential landscape.
For adoption on residential properties see TRCA's A Complete Guide to Maintaining a Rain Garden
==See Also==
*Bioretention
*Downspout disconnection
==External Links==
*Raingarden tour
*RainScapeTO
==Gallery==
==References==
category:infiltration