Urban Water-Quality Management: Rain Garden Plants

Authors: Mike Andruczyk, Extension Agent, Chesapeake; Lynnette Swanson, Extension Agent, Norfolk; Laurie Fox, Horticulture Associate, Hampton Roads Agricultural Research and Extension Center; Susan French, Extension Agent, Virginia Beach; Traci Gilland, Extension Agent, Portsmouth.

Publication Number 426-043, Posted July 2006.

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 fl ooding 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 fi ve 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 Use trees only in rain gardens larger than 150 square feet. Alder Alnus serrulata (glutinosa) Arborvitae Thuja occidentalis Atlantic White Cedar Chamaecyparis thyoides Austrian Pine Pinus nigra Bald Cypress Taxodium distichum Black Gum Nyssa sylvatica Carolina Silverbell Halesia tetraptera Common Persimmon Diospyros virginicus Dawn Redwood Metasequoia glyptostroboides Downy Serviceberry Amelanchier arborea Eastern Redbud Cercis canadensis Eastern Red Cedar Juniperus virginiana Green Ash Fraxinus pennsylvanica Hackberry Celtis occidentalis Hornbeam Carpinus caroliniana Japanese Cryptomeria Cryptomeria japonica Japanese Zelkova Zelkova serrata Katsura Tree Cercidiphyllum japonicum Lacebark Elm Ulmus parvifolia Loblolly Pine Pinus taeda Planetrees (Sycamores) Platanus spp. Red Maple Acer rubrum River Birch Betula nigra Swamp White Oak Quercus bicolor Sweetbay Magnolia Magnolia virginiana Sweetgum Liquidambar styraciflua Water Oak Quercus nigra Weeping Willow Salix babylonica/alba Willow Oak Quercus phellos Witch Hazel Hamamelis virginiana Yaupon Holly Ilex vomitoria Shrubs American Beautyberry Callicarpa americana Anise Illicium parvifolium Arrowwood Viburnum dentatum Bottlebrush Buckeye Aesculus parviflora Buttonbush Cephalanthus occidentalis Carolina Allspice Calycanthus floridus Chokeberry Aronia arbutifolia Cranberrybushes Viburnum opulus/trilobum Devilwood Osmanthus americana Dogwoods Cornus amomum/racemosam/ sericea Elderberry Sambucus canadensis False Indigo Amorpha fruticosa Fetterbush Leucothoe racemosa Groundsel Bush Baccharis halimifolia Highbush Blueberry Vaccinium corymbosum Inkberry Ilex glabra Leucothoes Leucothoe axillaris/fontanesiana Oakleaf Hydrangea Hydrangea quercifolia Possumhaw Ilex decidua Rose of Sharon Hibiscus syriacus Shadblow Serviceberry Amelanchier canadensis Spicebush Lindera benzoin Steeplebush Spiraea tomentosa Summersweet Clethra Clethra alnifolia Swamp Azalea Rhododendron viscosum Swamp Rose Rosa palustris Virginia Sweetspire Itea virginica Wax Myrtles Myrica cerifera/pennsylvanicum Willows Salix caprea/discolor/matsudana sachalinensis/purpurea Winterberry Ilex verticillata

Perennials Arrowhead Sagittaria latifola Asters Aster spp. Beardtongue Penstemon digitalis Beebalm Monarda didyma Blackeyed Susan Rudbeckia hirta Blue Lobelia Lobelia siphilitica Bluestar Amsonia tabernaemontana Calla Lily Zantedeschia spp. Canna Lily Canna spp. Cardinal Flower Lobelia cardinalis Crinum Lily Crinum spp. Daylilies Hemerocallis spp. Gingers Hedychium spp. Goldenrod Solidago flexicaulis Hardy Begonia Begonia grandis Hibiscus Hibiscus coccineus/moscheutos Ironweed Vernonia noveboracensis Irises Iris lousiana/pseudacorus/versicolor/ virginica Joe-Pye Weed Eupatorium spp. Leopard Plant Ligularia tussilaginea Liatris Liatris spicata Lilyturf Liriope muscari Lizard Tail Saururus cernuus Lungwort Pulmonaria spp. Marsh Marigold Caltha palustris Monkey Flower Mimulus ringens Obedient Plant Physotegia virginiana Pickerelweed Pontederia cordata Plantain Lily Hosta spp. Primroses Primula spp. Rain Lilies Zephyranthes spp. Red Columbine Aquilegia canadensis Siberian Bugloss Brunnera macrophylla Spiderwort Tradescantia spp. Strawberry Begonia Saxifraga stolonifera Swamp Milkweed Asclepias incarnata Swamp Sunflower Helianthus angustifolius Turtleheads Chelone lyonii/obliqua Virginia Bluebells Mertensia virginica Wild Ginger Asarum canadense Windflowers Anemone Ferns Christmas Fern Polystichum acrostichoides Cinnamon Fern Osmunda cinnamomea Holly Fern Cyrtomium falcatum Japanese Painted Fern Athyrium nipponicum Lady Fern Athyrium felix-femina Royal Fern Osmunda regalis Tassel Fern Polystichum braunii Wood Ferns Dryopteris spp. Grasses and Grass-like Broom Sedge Andropogon virginicus Feather Reed Grass Calamagrostis acutiflora Foxtail Grass Alopecurus pratensis Rushes Juncus spp. Sedges Carex spp. Sweetflag Acorus spp. Switchgrass Panicum virgatum Groundcovers Bugleweed Ajuga spp. Foamflower Tiarella cordifolia Green and Gold Chrysogonum virginianum Lilyturf Liriope spicata Mazus Mazus reptans Plumbago Ceratostigma plumbaginoides St. Johnswort Hypericum calycinum

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://www.ext.vt.edu/pubs/trees/430-295/430-295.html

A Guide to Successful Pruning: Pruning Basics and Tools, Virginia Cooperative Extension publication 430-455, http://www.ext.vt.edu/pubs/nursery/430-455/430-455.html

A Guide to Successful Pruning, Pruning Deciduous Trees, Virginia Cooperative Extension publication 430-456, http://www.ext.vt.edu/pubs/nursery/430-456/430-456.html

A Guide to Successful Pruning, Pruning Evergreen Trees, Virginia Cooperative Extension publication 430-457, http://www.ext.vt.edu/pubs/nursery/430-457/430-457.html

A Guide to Successful Pruning: Stop Topping Trees!, Virginia Cooperative Extension publication 430-458, http://www.ext.vt.edu/pubs/nursery/430-458/430-458.html

A Guide to Successful Pruning, Pruning Shrubs, Virginia Cooperative Extension publication 430-459, http://www.ext.vt.edu/pubs/nursery/430-459/430-459.html

A Guide to Successful Pruning, Decidous Tree Pruning Calendar, Virginia Cooperative Extension publication 430- 460, http://www.ext.vt.edu/pubs/nursery/430-460/430-460.html

A Guide to Successful Pruning, Evergreen Tree Pruning Calendar, Virginia Cooperative Extension publication 430- 461, http://www.ext.vt.edu/pubs/nursery/430-461/430-461.html

A Guide to Successful Pruning, Shrub Pruning Calendar, Virginia Cooperative Extension publication 430-462, http://www.ext.vt.edu/pubs/nursery/430-462/430-462.html

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 .

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