Urban Water-Quality Management: Rain Garden Plants
ID
426-043
A rain garden is a landscaped area specially designed to collect rainfall and storm-water runoff. The plants and soil in the rain garden clean pollutants from the water as it seeps into the ground and evaporates back into the atmosphere. For a rain garden to work, plants must be selected, installed, and maintained properly.
Plant Selection
- Choose plants tolerant of both occasional flooding as well as dry periods.
- Choose noninvasive plants that are adapted to the local environment.
- Choose a mixture of species. A good rule of thumb is one plant species for every 10 to 0 square feet. For example – a 140-square-foot garden would have 7 to 14 different plant species.
- Choose plants for vertical layering – a mix of tall-, medium-, and low-growing species.
Plant Installation
- Install plants in their proper moisture zones (see Fig. 1).
- Plant shrubs and perennials in groups of three to five of the same species. Trees can be planted in groups or individually.
- Plant taller and larger plants in the center or at one end of the garden, depending on the views.
- Plant shorter plants where they can be seen easily, around the garden edges, in front of larger plants, or underneath taller plants.
- Space and plant perennials so that their canopies will grow together and cover the ground to minimize weeds.
- Space and plant trees and shrubs according to their mature size. For example – beautyberry shrubs, that grow to six feet wide, should be planted three feet apart.
- Planting outside and around the rain garden area helps the garden blend into the overall landscape.
- More information can be found in Tree and Shrub Planting Guidelines, Virginia Cooperative Extension publication 430-295.
Figure 1. Rain garden.
Maintenance
- Add two to four inches of organic mulch to the entire newly planted rain garden. Do not cover the crowns of the perennials. Replenish mulch in the fall as needed.
- Avoid fine cut or lighter weight mulches as they tend to float in wet conditions.
- Prune any dead, diseased, or damaged plants as soon as the problem is noticed. More information on pruning woody plants can be found in Virginia Cooperative Extension publications 430-455 through 430-462 (see References).
- Prune the foliage of perennials when they die back for the winter and ornamental grasses before new growth begins in the spring.
- Remove or spot treat weeds as necessary.
- Water the garden during its establishment and extended dry periods. One inch of water per week is recommended.
Plant Lists
Trees, shrubs, and perennials are listed with both their common and scientific names. Ask at local garden centers for specific cultivars, varieties, and size at maturity.
Trees Alder Alnus serrulata (glutinosa) Shrubs | Perennials Ferns Grasses and Grass-like Groundcovers |
References
Rain Gardens, A Landscape Tool to Improve Water Quality; Virginia Department of Forestry Publication VDOF 000127, http://www.dof.virginia.gov/
Rain Gardens, Virginia Department of Forestry, http://www.dof.virginia.gov/rfb/rain-gardens.shtml
Backyard Rain Gardens, North Carolina Cooperative Extension, http://www.bae.ncsu.edu/topic/raingarden/
Rain Gardens, University of Wisconsi-Extension, http://clean-water.uwex.edu/pubs/raingarden/index.html
Rain Gardens, Rainscapes, http://209.142.214.237/rainscapes/garden.htm
Rain Gardens of West Michigan, http://www.raingardens.org/Index.php
Tree and Shrub Planting Guidelines, Virginia Cooperative Extension publication 430-295, http://pubs.ext.vt.edu/430-295/
A Guide to Successful Pruning: Pruning Basics and Tools, Virginia Cooperative Extension publication 430-455, http://pubs.ext.vt.edu/430-455/
A Guide to Successful Pruning, Pruning Deciduous Trees, Virginia Cooperative Extension publication 430-456, http://pubs.ext.vt.edu/430-456/
A Guide to Successful Pruning, Pruning Evergreen Trees, Virginia Cooperative Extension publication 430-457, http://pubs.ext.vt.edu/430-457/
A Guide to Successful Pruning: Stop Topping Trees!, Virginia Cooperative Extension publication 430-458, http://pubs.ext.vt.edu/430-458/
A Guide to Successful Pruning, Pruning Shrubs, Virginia Cooperative Extension publication 430-459, http://pubs.ext.vt.edu/430-459/
A Guide to Successful Pruning, Decidous Tree Pruning Calendar, Virginia Cooperative Extension publication 430-460, http://pubs.ext.vt.edu/430-460/
A Guide to Successful Pruning, Evergreen Tree Pruning Calendar, Virginia Cooperative Extension publication 430-461, http://pubs.ext.vt.edu/430-461/
A Guide to Successful Pruning, Shrub Pruning Calendar, Virginia Cooperative Extension publication 430-462, http://pubs.ext.vt.edu/430-462/
Editorial Contributors
Barry Fox, Extension Specialist, Virginia State University
Adria Bordas, Virginia Cooperative Extension Agent Fairfax County
Karen Carter, Virginia Cooperative Extension Agent Henrico County
JoAnne Gordon, Horticulturist, City of Norfolk
Rights
Virginia Cooperative Extension materials are available for public use, re-print, or citation without further permission, provided the use includes credit to the author and to Virginia Cooperative Extension, Virginia Tech, and Virginia State University.
Publisher
Issued in furtherance of Cooperative Extension work, Virginia Polytechnic Institute and State University, Virginia State University, and the U.S. Department of Agriculture cooperating. Alan L. Grant, Dean, College of Agriculture and Life Sciences; Edwin J. Jones, Director, Virginia Cooperative Extension, Virginia Tech, Blacksburg; Jewel E. Hairston, Administrator, 1890 Extension Program, Virginia State, Petersburg.
Date
May 1, 2009