While it might seem a little odd to discuss rain-friendly plants and stormwater gardens while wildfires rage and much of the country experiences drought, it’s good to be prepared. And rain gardens are the types of installations that are intended for the purpose of preparedness.
No matter what your particular microclimate offers, it’s a safe bet that there are periods of little rainfall, followed by moisture, either in the form of a gentle rain or a downpour. (Torrential rains resulting in disastrous flooding, such as much of the South has experienced this year, are still considered to be rare events, despite their seemingly increasing occurrence.) Even a 1-inch storm – during which 1 inch of rain is produced in a 24-hour period – can result in standing water and/or runoff. And that runoff may take some of the soil with it.
To help manage that wet-and-dry roller coaster, a rain garden may be just the ticket.
What is a rain garden?
Simply put, a rain garden is one that helps to mitigate rainfall and stormwater runoff by employing appropriate design – the right location – and appropriate plants. Right plant, right place? Precisely. But this a garden that’s designed with a twist.
The ideal rain garden is intended to withstand extremes, including periods of dry conditions followed by periods of inundation. Along with that inundation may come hours of standing water, often loaded with concentrated nutrients (such as nitrogen and phosphorus) found in stormwater runoff.
In addition, when properly sited, a rain garden may serve to slow stormwater runoff, allowing the moisture to percolate into the soil and preventing it from washing away the soil downslope. Plus, the plants that are specified for a rain garden help to clean the water of excess nutrients. It’s a win-win.
There are several types of rain gardens, ranging from simple catch basins featuring plants that don’t mind getting their feet wet, to those highly engineered sites that require grading and that employ below ground drainage systems. The design and installation of these gardens are fodder for another story; here we’ll address the plants.
Putting plants to work
The plants that perform well in a rain garden are myriad, ranging from perennials to grasses to small trees and shrubs. What they have in common is the ability to tolerate wet roots for the amount of time that it takes the rainwater to drain, which can be anywhere from a few hours to two days.
Plants in any garden should be pleasing; that’s a given. Pretty to look at is one thing; utilitarian is another. The perennial plants selected for a rain garden must be both.
Often selected to help leach nitrogen and phosphorus from the soil, thus preventing a nutrient overload, rain garden-ready perennials vary from region to region, from hardiness zone to hardiness zone. But there are hundreds of selections from which to choose.
Let’s take a look at what’s recommended around the country.
The Cooperative Extension Service of North Carolina State University and North Carolina A&T State University recommends the following perennials:
- Amsonia tabernaemontana (blue star)
- Asclepias incarnata (swamp milkweed)
- Aster carolinianus (climbing aster)
- Baptisia species (false indigo)
- Boltonia asteriodes (boltonia)
- Chelone glabra (turtlehead)
- Coreopsis lanceolata (tickseed)
- Eupatorium dubium (Joe Pye weed)
- Helianthus angustifolius (swamp sunflower)
- Hibiscus moscheutos (swamp mallow)
- Hibiscus coccineus (Texas star)
- Kosteletskya virginica (seashore mallow)
- Liatris spicata (gayfeather)
- Lobelia cardinalis (cardinal flower)
- Phlox paniculata (garden phlox)
- Rudbeckia fulgida (rudbeckia)
- Rudbeckia laciniata (green-headed coneflower)
- Solidago rugosa (goldenrod)
- Stokesia laevis (Stoke’s aster)
- Vernonia novaboracensis (ironweed)
- Verbena canadensis (verbena)
Up in western Pennsylvania, the Three Rivers Rain Garden Alliance recommends the following:
- Armeria maritima (sea thrift)
- Artemisia × ‘Powis Castle’ (‘Powis Castle’ artemisia)
- Artemisia schmidtiana ‘Silver Mound’ (silver mound artemisia)
- Hemerocallis spp. (daylily)
- Hosta plantaginea (hosta)
- Iberis sempervirens (candytuft)
- Limonium latifolium (sea lavender)
- Liriope spicata (lilyturf )
- Sedum spectabile ‘Autumn Joy’ (‘Autumn Joy’ sedum)
- Yucca filamentosa (Adam’s-needle yucca)
Over in Texas, Texas A&M’s AgriLife Extension offers a whopping 64 recommended perennials; we’ll include here a few of those not mentioned by Virginia or Pennsylvania.
- Achillea millefolium (yarrow)
- Acorus calamus (sweet flag)
- Adiantum capillus-veneris (Southern maidenhair)
- Alstromeria pulchella (Peruvian lily)
- Amorpha fruticosa (false indigo)
- Anisacanthus quadrifidus var. wrightii (flame acanthus)
- Aquilegia spp. (columbine)
- Aspidistra elatior (cast iron plant)
- Calyptocarpus vialis (horseherb)
- Canna generalis (canna)
- Crinum americanum (crinum lily)
- Delphinium virescens (prairie larkspur)
- Dichondra argentea ‘Silver Falls’ (silver falls)
- Echinacea purpurea (purple coneflower)
- Gaillardia spp. (blanketflower)
- Habranthus spp. (copper lily)
- Heliopsis helianthoides (ox-eyed sunflower)
- Iris spp. (iris)
- Kosteletzkya virginica (marsh mallow)
- Malvaviscus arboreus (giant Turk’s cap)
- Monarda didyma (bee balm)
- Oxalis bowiei (wood sorrel)
- Oenothera speciosa (pink evening primrose)
- Physostegia spp. (obedient plant)
- Ruellia spp. (Mexican petunia)
- Setcreasea pallida (purple heart)
- Sisyrinchium angustifolium (blue-eyed grass)
- Stachys byzantine (lamb’s ear)
- Tagetes lucida (Mexican mint marigold)
- Tradescantia occidentalis (spiderwort)
- Zephyranthes spp. (rain lily)
In the drylands of Colorado, Colorado State University’s Stormwater Center recommends the following natives:
- Achillea lanulosa (white yarrow)
- Aquilegia chrysantha (golden columbine)
- Dalea purpurea (purple prairie clover)
- Eriogonum umbellatum (sulphur flower)
- Gaillardia aristata (blanket flower)
- Ratibida columnifera (prairie coneflower)
And reaching out to the West Coast, the University of California’s Sonoma County Extension folks offer the following:
- Aralia californica (elk clover)
- Aristolochia californica (California pipevine)
- Darmera peltata (umbrella plant)
- Dicentra formosa (Pacific bleeding heart)
- Epipactis gigantean (stream orchid)
- Epilobium canum latifolium (California fuchsia)
- Erigeron glaucus (beach aster)
- Mimulus spp. (monkey flower)
- Mirabilis multiflora (giant four o’clock)
- Penstemon heterophyllus (beard tongue)
- Polypodium californicum (California polypody)
- Romneya coulteri (Matilija poppy)
- Salvia spp. (sage)