backyard raingardens
TRANSCRIPT
Backyard Rain Gardens
Kerrie RoachHorticulture Extension Agent
Henderson County
Do you need a Raingarden?
• Where is water pooling?
• Where is the water coming from?
• Where is the water going?
Steps
• Garden Location• Soils & Drainage• Sizing the Garden• Garden Construction• Plant Material• Examples
Garden Location• Not within 10’ of the foundation• 25’ from a septic drainfield• Not within 25’ of a well head• Avoid utility lines• Partial to full sun• Water table at least 2’ below
soil surface– If you hit the water table when
constructing your rain garden, consider turning it into a wetland garden.
Garden Location
• Consider…
– Diverting more water• downspouts
Soils & Drainage
• Best in well drained or sandy soils• Perc Test - Assess your site soil properties
– 1 foot hole– Fill with water– Let sit
Soils & Drainage
• There are three signs of an impermeable soil.– ponds water or remains saturated for several days after
storm event– shows signs of being a wetland soil within 1’ of surface
• A wetland soil is often gray with ribbons or areas of brown color.– Water poured in the hole is still there after two days
• Provided it has not rained
Sizing Your Garden
• Large or small– Depends on the drainage
area• Impermeable 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 Garden
• Example:– 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 area 60 X 60 3600 sq. ft.
¼ of the flow to downspouts (3600 sq. ft) X 25% 900 ft
Roof area plus driveway 900 + 500 1400 sq. ft
Divide square footage by 20 1400/20 70 sq. ft.
ANSWER The water garden should be at least 70 square feet.
A 5X14 or 7X10 foot garden design would be sufficient
Sizing Your RaingardenImpermeable Surface Area
Required 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 2 40 ft 2 4X10, 5X8, 6X7 80 ft 2 7X12, 8X10, 9X91000 ft 2 50 ft 2 5X10, 6X8 100 ft 2 7x15, 10X101200 ft 2 60 ft 2 4X15, 5X12, 6X10, 8X8 120 ft 2 10X12, 8X151400 ft 2 70 ft 2 5X14, 7X10 140 ft 2 10X14, 7X201600 ft 2 80 ft 2 7X12, 8X10, 9X9 160 ft 2 8X20, 10X161800 ft 2 90 ft 2 6X15, 7X13, 8X12, 9X10 180 ft 2 9X20,10X18,12X152000 ft 2 100 ft 2 7x15, 10X10 200 ft 2 10X20, 14X152500 ft 2 125 ft 2 8X16,10X13 250 ft 2 10X25, 13X20, 15X173000 ft 2 150 ft 2 10X15, 12X13 300 ft 2 10X30, 15X203500 ft 2 175 ft 2 9X20, 12X15 350 ft 2 14X25, 18X204000 ft 2 200 ft 2 10X20, 14X15 400 ft 2 16X25, 20X205000 ft 2 250 ft 2 10X25, 13X20, 15X17 500 ft 2 20X25
Garden Construction• Outline with string or paint• Dig!
– 4-6 inches deep– Slight depression in the middle– Soil on low side to create berm
Garden Construction
• Mulch or plant grass on berm• Add compost for well drained soils• Add mulch or gravel for compacted soils
Garden Construction
Plant Material• Fluctuating soil wetness
– Feast or famine!• Levels of planting
• Layout • Plant high or in mounds• Mulch with 2-3 inch thick
hardwood mulch• Water 2x/week until established
Examples
Examples
Examples
Maintenance
• Mulch annually• Minimize sediment• Weed, prune & water
– Especially during establishment!
• Keep it clean & healthy!
Questions?
• https://www.bae.ncsu.edu/topic/raingarden/index.htm