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Backyard Rain Gardens

Backyard Rain GardensKerrie RoachHorticulture Extension AgentHenderson County

Do you need a Raingarden?Where is water pooling?

Where is the water coming from?

Where is the water going?

Steps Garden LocationSoils & DrainageSizing the GardenGarden ConstructionPlant MaterialExamples

Garden LocationNot within 10 of the foundation25 from a septic drainfieldNot within 25 of a well headAvoid utility linesPartial to full sunWater table at least 2 below soil surfaceIf you hit the water table when constructing your rain garden, consider turning it into a wetland garden.

Garden LocationConsider

Diverting more waterdownspouts

NC 811Call before you Dig!www.nc811.org1-800-632-4949811

Soils & DrainageBest in well drained or sandy soilsPerc Test - Assess your site soil properties 1 foot holeFill with waterLet sit

Soils & DrainageThere are three signs of an impermeable soil.ponds water or remains saturated for several days after storm eventshows signs of being a wetland soil within 1 of surfaceA wetland soil is often gray with ribbons or areas of brown color.Water poured in the hole is still there after two daysProvided it has not rained

Sizing Your GardenLarge or smallDepends on the drainage areaImpermeable Drainage Area = (Sq. ft. roof area X percent draining to spout) + sq. ft. of pavement area Divide by 20 = Area Requirement for a depth of 6

Sizing Your GardenExample:A house is 60 feet by 60 feet and the owner estimates that 25% of the roof area is draining to the downspout. Further, she estimates that the driveway area draining to the location for the rain garden is 500 square feet. For a desired 6 inch ponding depth, what size should the rain garden be?Roof area60 X 603600 sq. ft. of the flow to downspouts(3600 sq. ft) X 25%900 ftRoof area plus driveway900 + 5001400 sq. ftDivide square footage by 201400/2070 sq. ft.ANSWERThe water garden should be at least 70 square feet.A 5X14 or 7X10 foot garden design would be sufficient

Sizing Your RaingardenImpermeable Surface AreaRequired Size of Rain Garden(6 deep)Potential Rain Garden Dimensions(ftXft)Required Size of Rain Garden(3 deep)Potential Rain Garden Dimensions(ftXft)800 ft 240 ft 24X10, 5X8, 6X780 ft 27X12, 8X10, 9X91000 ft 250 ft 25X10, 6X8100 ft 27x15, 10X101200 ft 260 ft 24X15, 5X12, 6X10, 8X8120 ft 210X12, 8X151400 ft 270 ft 25X14, 7X10140 ft 210X14, 7X201600 ft 280 ft 27X12, 8X10, 9X9160 ft 28X20, 10X161800 ft 290 ft 26X15, 7X13, 8X12, 9X10180 ft 29X20,10X18,12X152000 ft 2100 ft 27x15, 10X10200 ft 210X20, 14X152500 ft 2125 ft 28X16,10X13250 ft 210X25, 13X20, 15X173000 ft 2150 ft 210X15, 12X13300 ft 210X30, 15X203500 ft 2175 ft 29X20, 12X15350 ft 214X25, 18X204000 ft 2200 ft 210X20, 14X15400 ft 216X25, 20X205000 ft 2250 ft 210X25, 13X20, 15X17500 ft 220X25

Garden ConstructionOutline with string or paintDig!4-6 inches deepSlight depression in the middleSoil on low side to create berm

Garden ConstructionMulch or plant grass on bermAdd compost for well drained soilsAdd mulch or gravel for compacted soils

Garden Construction

Plant MaterialFluctuating soil wetnessFeast or famine!Levels of plantingLayout Plant high or in moundsMulch with 2-3 inch thick hardwood mulchWater 2x/week until established




MaintenanceMulch annuallyMinimize sedimentWeed, prune & waterEspecially during establishment!Keep it clean & healthy!