Rain Gardens and Bio-swales

Rain Gardens and Bio-swales can be a large part of sustainable Low Impact Development. Incorporating these design elements into your landscapes will help to take up excess water and filter it before it enters groundwater systems.

These areas mimic wetland natural areas and sometimes natural forested areas, with the mix and placement of plants. The effect is quiet lovely. Rain gardens and bio-swales can include a variety of plants including trees, shrubs, grasses and herbaceous plants. See our list below for more details.

Rain Gardens

A rain garden is a shallow landscape depression with native soil or a soil mix and plants that can capture stormwater from small, adjacent contributing areas. They generally are areas with sloping sides so different plants can be employed at various levels, depending on how much moisture they can retain and use. Plants in rain gardens can withstand standing water and often have systems that work to absorb excess water, rather than allowing it to runoff and erode native soils.

Bio-swales

Biorention swales are similar to rain gardens in that they are a depressed area of plants and soil, used to catch excess stormwater and runoff. Bio-swales are designed with even more drainage solutions in mind, as part of a system that can handle large quantities of runoff when other systems are flooded. Bio-swales are often built in low-lying areas where water tends to naturally collect. Plants can be used to take up some of the excess and to create a handsome and hospitable landscape environment. However, optional under-drains can be included to help direct excess water to proper storm drains. Additionally, gradient controls, such as check dams, gravel mulch and catch basins, are used to reduce flow and manage erosion and sediment buildup.

Where to Use Them

Rain gardens and bio-swales can be employed on a small or large scale. These can be used in both residential and commercial properties to prevent flooding, improve drainage and deal with excess water on a property. They do not need to take up much space. Rain gardens can be installed in parking lot and round-about islands. They work well in landscaped areas of apartment complexes and shopping centers. Bio-swales work well along road ways and ditches, where water naturally pools.

Order Now

Take a look at our list of perennials, grasses, shrubs and other plants that are compatible with Low Impact Development. You can order any of these plants today. Give us a call with your orders and questions at 1-866-816-5080

Zone 1 Trees

Species/Common Name	Exposure	Mature Size	Bloom Time	Comments
Alnus rubra Red alder	Sun/part shade	30′-120′ high and 25′ wide		Highly adaptable, drought tolerant, nitrogen fixer
Salix lucida Pacific willow	Sun	40′-60′ high and 30′ wide		Tolerates seasonal flooding, do not plant near pavement or underground structures
Fraxinus latifolia Oregon ash	Sun/part shade	40′-80′ high and 30′ wide		Flood tolerant, small green-white flowers
Malus fusca Pacific crabapple	Sun/part shade	To 40′ high and 35′ wide	Spring	Tolerant of soil saturation, produces fruit, not recommended to get in larger than #5 pot.

Zone 1 Shrubs

Species/Common Name	Exposure	Mature Size	Bloom Time	Comments
Lonicera involucrata Black twinberry	Part shade/shade	2′-8′ high	April-May	Tolerant of shallow flooding, yellow tubular flowers attract hummingbirds
*Myrica californica Pacific wax myrtle	Sun/part shade	To 30′ high	May-June	Inconspicuous spring flowers, drought tolerant once established
Physocarpus capitatus Pacific ninebark	Sun/part shade	6′-13′ high	May-June	Drought tolerant, white flowers, seeds persist into winter
Rosa pisocarpa Clustered wild rose	Sun/part shade	6′-8′ high	May-July	Tolerates seasonal flooding but also tolerant of dry conditions, pink clustered flowers
Salix purpurea ‘Nana’ Dwarf arctic willow	Sun/part shade	3′-5′ high		Grows well in poor soils, moderately drought tolerant, small yellow flowers
Spiraea douglasii Douglas spiraea	Sun/part shade	4′-7′ high		Takes seasonal inundation, spikes of small pink flower clusters

Zone 1 Emergents

Species/Common Name	Exposure	Mature Size	Bloom Time	Comments
Carex obnupta Slough sedge	Sun/part shade	1′-5′ high		Takes seasonally saturated soils, shiny foliage, excellent soil binder and drought tolerant
Carex stipata Sawbeak sedge	Part shade	10”-3′ high		Takes wet soil, excellent soil binder
*Juncus effuses Common rush	Sun/part shade	1′-2′ high	Summer	Hardy and adaptable, drought tolerant, small non showy flowers
Juncus ensifolius Daggerleaf rush	Sun	12”-18” high		Wet soils, shallow water, excellent soil binder
Juncus tenuis Slender rush	Sun	.5′-2.5′ high		Moist soils, tufted perennial
Scirpus acutus Hardstem bulrush	Sun	4′-8′ high		Favors prolonged inundation, excellent soil binder
Scirpus microcarpus Small-fruited bulrush	Sun/shade	2′-4′ high		Tolerates prolonged inundation, good soil binder, drought tolerant

Zone 2 Trees

Species/Common Name	Exposure	Mature Size	Bloom Time	Comments
Acer truncatum Pacific, sunset maple	Sun	To 25′ high and 20′ wide		Drought tolerant, very cold hardy, moderate growth rate
Amelanchier alnifolia Western serviceberry	Sun/part shade	10′-20′ high and 25′ wide	April – May	Drought tolerant, large white flowers, purple to black berries, rust can be a big problem
Corylus cornuta Beaked hazelnut	Sun/part shade	20′-30′ high and 15′ wide	April – May	Edible nuts, intolerant of saturated soils, catkins hold through winter
Crataegus douglasii Black hawthorn	Sun/part shade	20′-30′ high and 25′ wide	Spring	Gravelly soils, small white flowers, black berries, 1” spines forms thickets
Fraxinus oxycarpa Raywood ash	Sun	25′-50′ high and 25′ wide	Spring	Drought tolerant, grows in variety of soil types, can take extreme temperatures will not tolerate constant wind or fog, resists pests and disease
Rhamnus purshiana Cascara	Sun/shade	20′-40′ high and 25′ wide		Small greenish-yellow flowers, sensitive to air pollution, yellow fall color
Salix scouleriana Scouler willow	Sun/part shade	6′-40′ high and 25′ wide		Drought tolerant, do not plant near paved surfaces or underground structures
Salix sitchensis Sitka willow	Sun/part shade	3′-26′ high and 25′ wide		Tolerates seasonal flooding, do not plant near paved surfaces or underground structures
*Thuja plicata Western red cedar	Part shade/shade	200’+ and 60′ wide		Tolerates seasonal flooding and saturated soils, long lived and prefers shade when young

Zone 2 Shrubs

Species/Common Name	Exposure	Mature Size	Bloom Time	Comments
Acer circinatum Vine maple	Filtered sun/shade	To 25′	Spring	Tolerant of shade and clay soils, excellent soil binder, beautiful fall color
Hamamellis intermedia Diane witchhazel	Sun/part shade	10′-20′ high and 10′ wide	January-March	Showy fall color, yellow orange, long lasting, fragrant coppery-red flowers, not drought tolerant, requires watering
Oemleria cerasiformis Indian plum/Osoberry	Sun/part shade	5′-16′ high	February-March	Prefers shade, tolerates fluctuating water table
Philadelphus x lemoinei ‘Belle Etoile’ Mock Orange	Sun/part shade	5′-6′ high	May-June	Soil and pH adaptable, easily transplanted and established, fragrant, large white flowers, tinged red at base.  Variety is hard to find but species is not
Ribes lacustre Black swamp gooseberry	Part shade	1.5′-3′ high		Reddish flowers in drooping clusters, dark purple berries
Rosa nutkana Nootka rose	Sun/part shade	6′-10′ high	April-June	Tolerates inundation and saturated soils, aggressive spreader, fruits persist, less thorny then R. rugosa
Rosa rugosa Rugosa rose varieties	Sun	To 8′ high		Drought resistant, hardy, vigorous and aggressive, highly prickly, fragrant white to purple flowers, fruits persist
Rubus parviflorus Thimbleberry	Sun/part shade	4′-10′ high	May-June	White flowers, red berries, will make thickets and spreads easily
Rubus spectabilis Salmonberry	Part sun/shade	5′-10′ high	February-April	Good soil binder, magenta flowers, yellow/orange fruit, early nectar source for hummingbirds, makes thickets
Sambucus racemosa Red elderberry	Part sun/part shade	To 20′ high	April-May	Small white flowers, bright red berries, vase shaped, pithy stems lead to messy form, prune for tidiness
Symphoricarpos albus Snowberry	Sun/part shade	2′-6′ high		Excellent soil binder, drought and urban air tolerant, provides good erosion control, spreads well in sun
Vaccinium parviolium Red huckleberry	Part shade/shade	4′-10′ high		Prefers loamy, acid soils or rotting wood, tolerant of dry, shady areas, red fruit, trick to transplant, low availability

Zone 2 Herbaceous

Species/Common Name	Exposure	Mature Size	Bloom Time	Comments
Aquilegia formosa Western columbine	Sun/part shade	1′-3′ high	Spring	Tolerant of seasonal flooding, red and yellow flowers attract hummingbirds and butterflies
Asarum caudatum Wild ginger	Part shade/shade	To 10” high	Mid spring	Heart shaped leaves, reddish brown flowers
Aster chilensis Common California aster	Sun	1.5′-3′ high	June-September	Moist soils, white to purple flowers
Aster subspicatus Douglas aster	Sun	.5′-2.5′ high	June-September	Moist soils, blue to purple flowers
Camassia quamash Common camas	Sun/part shade	To 2.5′ high	May-June	Lots of watering needed to establish, loose clusters of deep blue flowers
Camassia leichtilnii Giant camas		2′-4′ high	May-June	Need lots of watering to establish, large clusters of white, blue or greenish-yellow flowers
Iris douglasiana Pacific coast iris	Sun/part shade	1′-2′ high	Spring	Withstands summer drought and seasonal flooding, white, yellow, blue, reddish-purple flowers, fast growing
Iris foetidissima Gladwin iris	Sun/part shade	1′-2′ high	May	Well drained soils, pale lilac flower, also called stinking iris
Juncus tenuis Slender rush	Sun	.5′-2.5′ high		Moist soils, yellow flowers
Iris siberica Siberian Iris	Sun	1′-2.5′ high	Late spring	Moist soils, deep blue, purple to white flowers
Tellima grandiflora Fringecup	Part sun/shade	1′-3′ high	March-June	Prefers moist soils, yellowish-green to pink flowers
Tiarella trifoliate Foamflower	Part sun/shade	To 1′ high	Early-mid summer	Moist soils, some drought tolerance after established, can form dense colonies
Tolmiea menziesii Piggy-back plant	Part shade/shade	1′-2′ high	April-August	Brownish purple flowers, makes and effective ground cover
Viola species Violet	Part shade/shade	.5′-1′ high	Late spring-early summer	Moist soils, yellow to blue flowers

Zone 3 Trees

Species/Common Name	Exposure	Mature Size	Bloom Time	Comments
Cornus spp. Dogwood	Sun/part shade		20′-30′ high and 30′ wide	May	Reliable flowering trees with attractive foliage and flowers, may need water in summer
Prunus emarginata Bitter cherry	Sun/part shade		20′-50′ high and 20′ wide	May-June	Intolerant of full shade, purple to black cherries, roots spread extensively and tree’s have high mortality rate
Prunus virginana Choke cherry			3′-25′ high and 15′-20′ wide	Late spring-early summer	Dry or moist soils, deep rooting, attractive white fragrant flowers, good fall color, low availability
*Pseudotsuga menziesii Douglas fir	Sun		100′-250’  high and 50′-60′ wide		Medium to fast rate of growth, provides a nice canopy but potential will restrict placement
Quercus garryana Oregon white oak	Sun		To 75′		Dry to moist, well drained soils, slow growing, has acorns

Zone 3 Evergreen Trees

Species/Common Name	Exposure	Mature Size	Bloom Time	Comments
*Arbutus unedo Strawberry tree	Sun/part shade		8′-35′ high and 8′-20′ wide	November-December	Tolerant of extremes, tolerant of urban/industrial pollution, white or greenish white flowers
*Calocedrus decurrens Incense cedar	Sun		75′-90′ high and 12′ wide		Tolerant of poor soils, drought tolerant after established, narrow growth habit, slow growing
*Chamaecyparis obtuse Hinoki false cypress	Sun/part shade		40′-50′ high and 25′-30′ wide		Very slow growing, prefers sun but tolerates shade, does not transplant well or do well in alkaline soils
*Pinus mugo Swiss mountain pine	Sun/part shade		15′-20′ high and 25′-30′ wide		Slow growing, broadly spreading, bushy tree, hardy evergreen
*Pinus thunbergiana Japanese black pine	Sun		To 100′ high and 40′ wide		Prefers dry to moist soils, hardy, fast growing, low availability

Zone 3 Shrubs

Species/Common Name	Exposure	Mature Size	Bloom Time	Comments
Holodiscus discolor Oceanspray	Sun/part shade		To 15′ high	June-July	Dry to moist soils, drought-tolerant, white to cream flowers, good soil binder
Philadelphus lewisii Mock-orange	Sun/part shade		5′-10′ high	June-July	Adapts to a variety of soils, drought tolerant, fragrant flowers
*Pinus mugo pumilo Mugho pine	Sun		3′-5′ high and 4′-6′ wide		Adapts to moist soils, slow growing and very hardy
Potentilla fruticosa Shrubby cinquefoil	Sun		To 4′ high	May-September	Moist to dry soils, several cultivars available with varying foliage and flower hues
Potentilla gracillis Graceful cinquefoil	Sun		1′-2′ high	July	Moist to dry soils, yellow flowers
Ribes sanguineum Red-flowering currant	Sun/part shade		8′-12′ high	March-April	Prefers dry soils, drought tolerant, white to deep-red flowers attract hummingbirds, thornless
Rosa gymnocarpa Baldhip rose	Part shade		To 6′ high	May-July	Dry or moist soils, drought tolerant, small pink to rose flowers

Zone 3 Evergreen Shrubs

Species/Common Name	Exposure	Mature Size	Bloom Time	Comments
*Abelia x grandiflora Glossy abelia		Part sun/part shade	To 8′ high and 5′ wide	Summer	Prefers moist, well drained soils but drought tolerant, white or faint pink flowers
*Arbutus unedo ‘Compacta’ Compact strawberry tree		Sun/part shade	To 10′ high	Fall	Tolerant of poor soils, good in climate extremes, white to greenish white flowers, striking red/orange fruit
*Cistus purpureus Orchid rockrose		Sun	To 4′ high	June-July	Drought resistant, fast growing, reddish purple flowers
*Cistus salviifolius White rockrose		Sun	2-3′ high and 6′ wide	Late spring	Tolerates poor soils, tolerant of windy conditions and drought, white flowers
*Escallonia x exoniensis ‘fradesii’ Pink Princess Escallonia		Sun/part sun	5′-6′ high	Spring-fall	Drought tolerant when established, pink to rose colored flowers, good hedge or border plant, attracts butterflies.
*Osmanthus delavayi Delavay Osmanthus		Sun/part shade	4′-6′ high	March-May	Tolerant of a variety of soils, attractive foliage and clusters of white fragrant flowers, slow growing
*Osmanthus x burkwoodii Burkwood osmanthus		Sun/part shade	4′-6′ high	March-April	Drought tolerant once established, masses of small, white fragrant flowers
*Rhododendron ‘PJM’ PJM Rhododendron		Sun/part shade	To 4′ high	Mid-late April	Moist to fairly dry soils, well drained organic soil, lavender to pink flowers
*Stranvaesia davidiana Chinese photinia		Sun	6′-20′ high	June	Moist soils, white flowers in clusters, showy red berries, low availability
*Stranvaesia davidiana undulata Prostrate stranvaesia		Sun	To 5′ high	June	Moist soils, lower growing irregularly shaped shrub, great screening plant. Has very low availability
*Vaccinium ovatum Evergreen huckleberry		Sun/part shade	3′-15′ high	March	Moist to slightly dry soils, small pinkish white flowers, edible berries in August

Zone 3 Evergreen Groundcover

Species/Common Name	Exposure	Mature Size	Bloom Time	Comments
*Arctostaphylos uva-ursi Kinnikinnick		Sun/part shade		April-June	Prefers sandy/rocky, well drained soils, flowers pinkish white, bright red berries, slow to establish, plant closely
*Gaultheria shallon Salal		Part shade/shade	3′-7′ high	March-June	White or pinkish flowers, reddish-blue to dark-purple fruit
*Fragaria chiloensis Wild strawberry		Sun/part shade	10” high	Spring	Sandy well drained soils, flowers white, aggressive spreader
*Helianthemum nummularium Sunrose		Sun	To 2′ high and wide	May-July	Will tolerate many soil types, woody perennial, many varieties are available with varying flower colors
*Lavandula angustifolia Lavender		Sun/part shade	To 1.5′ high	June-August	Adaptable to variety of soils, blue, lavender, pink to white flowers, semi evergreen, aromatic. Does not like PNW wet winters
*Mahonia nervosa Cascade Oregon Grape		Sun/part shade	To 2′ high	April-June	Dry to moist soils, drought resistant, yellow flowers, blue berries
*Mahonia repens Creeping mahonia		Sun/part shade	3′ high	April-June	Dry to moist soils, drought resistant, yellow flowers, blue berries
*Penstemon davidsonii Davidson’s penstemon		Sun	To 3” high	June-August	Low growing evergreen, prefers well drained soils, drought tolerant, blue to purple flowers.

Zone 3 Perennials & Ornamental Grasses

Species/Common Name	Exposure	Mature Size	Bloom Time	Comments
Achillea millefolium Western yarrow		Sun			4”-2.5′ high	June-September	Dry to moist, well drained soils, white to pink/reddish flowers
Anaphalis margaritaceae Pearly everlasting		Sun/part shade			To 18” high		Drought tolerant perennial, spreads quickly, attracts butterflies
Bromus carinatus California brome		Sun/part shade			3′-5′ high		Dry to moist soils, tolerates seasonal saturation, low availability
Carex buchanaii Leather leaf sedge		Sun/part shade			1′-3′ high		Copper-colored foliage, perennial clumping grass, tolerant of many soils
Carex comans ‘Frosty Curls’ New Zealand hair sedge			Sun/part shade		1′-2′ high	June-August	Finely textured and light green, compact, clumping perennial grass, drought tolerant when established
Coreopsis spp. Tickseed		Sun			1′-3′ high		Dry to moist soils, drought tolerant, seeds attract birds, annual and perennial varieties
Echinacea purpurea Purple coneflower		Sun			4′-5′ high		Prefers well drained soils, hardy perennial, may need water in dry times
Elymus glaucus Blue wildrye		Sun/part shade			1.5′-5′ high		Dry to moist soils, shade tolerant, rapid developing but short lived (1-3 years) do not use as lawn grass
Dicentra Formosa Pacific bleeding heart		Sun/shade			6”-20” high	Early spring-early summer	Moist, rich soils, heart shaped flowers
Erigeron speciosus Showy fleabane		Sun/part shade			To 2′ high	Summer	Moist to dry soils, dark violet or lavender blooms, fibrous roots
Festuca ovina ‘Glauca’ Blue fescue		Sun/part shade			To 10” high	May-June	Blue-green evergreen grass, drought tolerant, shearing will stimulate new growth
Festuca idahoensis Idaho fexcue		Sun/part shade			To 1′ high		Bluish-green bunching perennial grass, drought tolerant
*Fragaria vesca Wood strawberry		Part shade			To 10” high	Late spring-early summer	Dry to moist soils, white flowers
Gaultheria shallon Salal		Sun/shade			3′-7′ high	March-June	Dry and moist soils, white or pinkish flowers, reddish-blue to dark-purple fruit
Gaura lindheimeri Gaura		Sun			2.5′-4′ high		Perennial, fairly drought tolerant and adaptable to varying soil types
Geum macrophyllum Large-leaved avens		Sun/part shade			To 3′ high	Spring	Bright yellow flowers, other cultivars available, some may require more water
Geranium maculatum Spotted geranium		Sun/shade			To 1.5′ high	July	Moist, well drained soils, low perennial, pale pink, blue to purple flowers, low availability
Geranium sanguineum Cranesbill		Sun/part shade			To 1.5′ high	May-August	Moist soils, deep purple, almost crimson flowers
*Helichrysum italicum Curry plant		Sun			To 2′ high	Summer	Hardy evergreen perennial, good companion to lavender, bright yellow fragrant flowers, low availability
*Helictotrichon sempervirens Blue oat grass				Sun/part shade	1′-1.5′ high	June-August	Clumping bright blue evergreen grass, bluish white flowers
Hemerocallis fulva Day lilies		Sun/part shade			1′-4′ high	Summer	Easy to grow and tolerant of neglect, hardy perennial, entire plant is edible
Heuchera americana Coral bells		Sun/part shade			1′-2′ high	June-August	Easily transplantable perennial, red, greenish-white flowers, may need supplemental watering in dry season
*Heuchera micrantha ‘Palace Purple’		Sun/part shade			1′-2′ high	June-August	Bronze to purple foliage in shade, small yellowish flowers, evergreen perennial
Lupinus Lupines		Sun			3′-5′ high	March-September	Various native varieties, blue to purple, violet to white flowers
Lupinus bicolor Two color lupine		Sun			4”-1.5′ high	Spring	Dry gravelly soils, small flowered annual
Lupinus latifolius Broadleaf lupine		Sun			To 1′ high	June-August	Dry to moist soils, perennial, bushy herb, bluish flowers, low availability
Lupinus polyphyllus Large-leafed lupine		Sun			To 3′ high	Spring-summer	Dry to moist, sandy to gravelly soils, perennial
Mahonia aquifolium Tall Oregon grape		Sun/part shade			6′-10′ high	March-April	Drought resistant evergreen, blue-black fruit, bright yellow flowers, great low screening barrier
Maianthemum dilatatum False lily-of-the-valley		Part shade/shade			3”-12” high	Spring	Moist soils, small white flowers, light green to red berries
Pennisetum alopecuroides Fountain Grass		Sun/part shade			1′-2′ high	August-September	Tolerant of many soil types, clump forming grasses
Pennisetum orientale Oriental fountain grass		Sun/part shade			1′-3′ high	June-October	Somewhat drought tolerant, small clumping, blooming grass, showy pink flowers
*Penstemon fruticosus Bush penstemon		Sun			8”-10” high	May	Prefers well drained soils, evergreen perennial, drought tolerant, violet blue flowers 1” long attract hummingbirds
*Polystichum munitum Swordfern	Part shade/deep shade				2′-4′ high		Prefers moist, rich soil conditions but drought tolerant, large evergreen fern
Rudbeckia hirta Black-eyed susan		Sun/part shade			3′-4′ high	Summer	Moist to dry soils, showy flowers, hardy and easy to grow
Smilacina racemosas False solomons seal		Part sun/shade			1′-3′ high	April-May	Moist soils, creamy white flowers, red berries
Solidago Canadensis Canadian goldenrod		Sun/part shade			1′-2′ high	Late summer-early fall	Dry to moist soils, yellow flowers