Monday, March 23, 2015

Rain gardens for clay soil in full sun

"Plants can adapt. 
They have done so for thousands of years and will continue to do so. 
Concrete cannot."
-Emily DeBolt



With climate change, how do we manage stormwater runoff from more frequent large storm events at unpredictable times? We need to design systems that can recover,  planning ahead with back up plans.   Green infrastructure systems such as rain gardens and other bioretention systems, can be more resilient than traditional gray infrastructure systems, such as dry wells and catch basins.


Instead of allowing rainwater to flow into storm drains, increasing flooding and municipal overflow, rainwater soaks into the soil in rain gardens recharging the water table.  Rain garden plants provide habitat for birds and butterflies as well.




The soil will retain the greatest amount of moisture at the center of your garden and should be planted with species native that tolerate wet, clay soils and that are native to your area. Note that these plant lists are most appropriate for the Northeast and upper Midwest:

Wildflowers
Sweet flag (Acorus calamus)
Swamp milkweed (Asclepias incarnata)
New England Aster (Aster novae-angliae)
Turtlehead (Chelone glabra)
Joe Pye Weed (Eupatorium maculatum)
Boneset (Eupatorium perfoliatum)
Prairie Blazing Star (Liatris pycnostachya)
Great Blue Lobelia (Lobelia siphilitica)
Mountain Mint (Pycnanthemum virginianum)
Blue Vervain (Verbena hastata)
Common Ironweed (Vernonia fasciculata)
Grasses
Fringed brome (Bromus ciliatus)
Porcupine Sedge (Carex hystericina)
Fox Sedge (Carex vulpinoidea)
Cord Grass (Spartina pectinata)

Species suited to the drier soil on the upper edges of the rain garden include:

Wildflowers
Nodding Pink Onion (Allium cernuum)
Lead Plant (Amorpha canescens)
White Wild Indigo (Baptisia leucantha)
Beardtongue (Penstemon digitalis)
Purple Prairie Clover (Petalostemum purpureum)
Black-eyed Susan (Rudbeckia hirta)
Stiff Goldenrod (Solidago rigida)
Grasses
Sideoats Grama (Bouteloua curtipendula)
Prairie Brome (Bromus kalmii)
Copper-shouldered oval sedge (Carex bicknellii)
Narrow-leaved oval sedge (Carex squarrosa)

Possible rain garden plants including non-natives  

TypesPlantings
spring/early summer bloomersred milkweed
shooting star
wild iris
summer bloomersnodding pink onion
prairie blazing star
late summer/fall bloomersNew England aster
Ohio goldenrod
sweet black-eyed Susan
grassesIndian grass
prairie drop seed
ornamental optionsNot only can these plants tolerate wet conditions, they also can withstand our Upper Midwest winters. Mixing trees, shrubs, flowers, and ground covers to create different plant levels will attract a greater diversity of wildlife to your garden.
treesred maple (prefers acid soil)
river birch
swamp white oak
shrubsglossy black chokeberry
northern lights azalea (prefers acid soil)
red-osier dogwood
perennials and annualsasters
astilbe
companula
cardinal flower
hosta
orange coneflower
salvia
Siberian iris
ground covers and fernscreeping willow
dwarf arctic willow
(Most mosses do well in moist, acid soils. Ferns need moist yet relatively well-drained soils.)
plants in wetland standsWetland gardens may have three zones – one in which plants are in for some occasional wading, one in which they continually have wet feet, and one in which they are completely immersed. Select plants accordingly.
wet meadow/prairie (occasionally wet feet, dry tops)blue lobelia
boneset
fox sedge
Joe Pye weed
ironweed

meadow rue
New England aster
porcupine sedge
red cardinal flower
red milkweed
switchgrass
turtlehead
emergent (feet in permanent pool, dry tops)blue flag iris
marsh marigold
pickerelweed
softstem bulrush
sweet flag
wapato duck potato
water plantain
submergentnative lilypad
Chara







Another option for implementing some storm water management in a clay-rich garden site is to replace turf grass with wet-tolerant native plants without creating a depression. Native plants will greatly improve the clay site by making the best use of water and soil resources, and also build up the soil. Landscaping in clay without a depression will not technically create a rain garden, but runoff will still be reduced since deep-rooted natives create channels for infiltration in even the tightest clay soils. This garden will also attract desirable wildlife and beneficial insects. Some wet prairie species that grow in clay soils include blue flag iris (Iris versicolor), water plantain (Alisma subcordatum), porcupine sedge (Carex hystericina), and some bulrushes (Scirpus atrovirens, Scirpus acutus).


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