In areas where runoff rainwater or overflow is a concern for causing soil erosion and the possible spread of chemical pollutants, pesticides, or sediment into the watertable, stormwater catchment allows for precipitation to be redirected into the landscape to benefit plantings of perennials tolerant of “wet feet”. One strategy for stormwater catchment is the installation of rain gardens–sunken basins which capture and absorb runoff in the landscape. Rain gardens are typically planted with water-loving and fibrous-rooted plants such as iris (Iris versicolor) and calamus (Acorus calamus), and trees such as Black Gum (Nyssa sylvatica), but edible plants can be included as well. The Philadelphia Orchard Project has been involved with pilot projects incorporating fruiting and edible plant materials into rain garden plantings at some of its partner schools. In 2009, POP worked with Greening Greenfield and the Philadelphia Water Department (PWD) on a project that incorporated juneberries (Amelanchier spp) and paw paws (Asimina triloba) into rain garden beds at Greenfield Elementary in Center City. This fall, POP collaborated with Greening Lea, PWD, the Netter Center, and other partners on a project that incorporated blueberries (Vaccinium), chokeberries (Aronia), paw paws, and fiddlehead ferns (Matteuccia) into new rain gardens at Lea Elementary School in West Philadelphia. What could be better than replacing paved schoolyards with multi-functional green infrastructure?
There are several primary types of rain gardens. The simplest consist of terraformed basins sunk below the level of the surrounding landscape, while others include subsurface gravel pits and/or cisterns for additional water storage. Depending on the size and scale, some engineering is required to calculate capacity and ensure effective stormwater management.
Rainwater harvesting using rain barrels, cisterns, or other means of storage is another effective strategy for stormwater management that can aid in transforming the negative effects of runoff into a positive resource. If rainfall in the eastern United States amounts to 40 inches annually, as estimated in Gaia’s Garden: A Guide to Home-Scale Permaculture, it’s calculated that that the average 1,000 square-foot residential roof will save 25,000 gallons of water annually – enough to keep a 1,000 square-foot garden watered for 250 days of drought! (p 106)
Various types of stormwater catchment barrels
Storage drums and tanks needn’t be an eyesore, either! Some are designed as planters from the outset to lend a distinctive look to a garden. Others, if buried to be half-recessed in the ground, can be overplanted with showy ornamentals to make the tank less obtrusive. Hooked up to a roof’s downspout, barrels collect water (oftentimes topped with metal screening to prevent debris and insects from entry), and hoses and drip irrigation water lines can be connected to carry the collected water out and into the garden.
Many resources exist online for such systems, such as the Harvest H20 community, which provides lots of information on choosing a tank, working with purification filters, and shares success stories of homeowners, schools, and civic buildings that have made use of stormwater management, achieving beneficial results in terms of lessening water use and consumption.
In Philadelphia, free 55-gallon water barrels are available to interested residents along with education, planters, and porous pavers, as part of Rain Check, a Philadelphia Water Department program now managed through PHS that helps residents manage stormwater at their homes. Since June 2011, 1,100 barrels have been incorporated throughout the city, and it’s estimated that stormwater pollution will have been reduced by 85 percent!
Edible Rain Gardens and Water-Loving Perennials
Rain gardens that draw upon the five-fold combination of rich compost to hold moisture, contours that allow for runoff to be held and disbursed through underground channels, swales (shallow trenches that can become saturated with water), and dense and well-mulched plantings that keep the soil cool and prevent plants’ transpiration are a key strategy for conserving water until it’s absorbed by the soil.
Choosing a wide variety of native plants, attractive ornamentals, and pollinator-friendly plants, in addition to edibles and medicinals, contributes to a healthy and vital ecosystem that honors the balance of resources and relationships and provides the greatest benefit for filtering stormwater and runoff. LowImpactDevelopment.org is a great resource for those planning a rain garden, providing sample templates, designs, and plant lists.
Choose plants that are suited to the drainage your soil receives! A distinguishing characteristic of rain gardens is that plants contained within must withstand wet roots that take anywhere from 24 to 48 hours to drain. Consider adding the following water-loving species to your rain garden:
Fruiting Edibles: Chokeberry (Aronia spp.), Cranberry (Vaccinium macrocarpon), Elderberry (Sambucus spp.), High-bush blueberry (Vaccinium corymbosum), High-bush cranberry (Viburnum trilobum), Paw paw (Asimina triloba), Currants (Ribes rubrum/ nigrum), Gooseberries (Ribes uva-crispa,), Jostaberries (Cross between Currants and Gooseberries), Raspberries (Rubus spp.), Cranberry (Vaccinium macrocarpom), Salmonberries (Rubus spectabilis), Huckleberries (Vaccinium ovatum), Elderberry (Sambucus caerulea/nigrum), Salal (Gaultheria shallon), Wild Ginger (Asarum caudatum)
Herbaceous edibles: Ostrich Fern (Matteuccia struthiopteris), Cattail (Typha spp.), Asparagus (Asparagus officinalis), Daylily (Hemerocallis fulva), Taro (Colocasia esculenta)
Medicinals: Comfrey (Symphytum officinale), Horsetail (Equisetum spp.), Sweet Flag (Acorus calamus), Taro (Colocasia esculenta), Daylily (Hemerocallis fulva), Hawthorn (Crataegus spp.), Yaupon (Ilex vomitorium)
For more information on water conservation and constructing a resilient ecosystem in the face of runoff, consult the following resources:
Gaia’s Garden: A Guide to Homescale Permaculture: 2nd Edition by Toby Hemenway
This edition of POP Tips researched and compiled by 2015 POP Outreach Intern, Alyssa Schimmel.