Lecture Notes How to Design and Build Your Rain Garden 1. Storm Water Run Off Evaluation o Sketch the property o Wait for rain not at the beginning of a storm not during the first storm after a dry spell o Walk the property record run off observations note high and low spots downspouts, impervious surfaces, steep terrain, etc. 2. Determine a location o What do you want to do? roof run off lawn run off driveway, walkway or patio run off o Do you wan the garden in a different location? underground pipes swales o Other factors to consider 10 feet down hill of the building beyond the drip line of a tree away from septic systems and utilities avoid steep slopes avoid areas that don’t drain soil type‐ sand, silt, clay o The garden MUST drain. o Infiltration test test hole 6‐12 inches wide and 12 inches deep add water refill if dry season look for complete drainage in 24‐48 hours amending the soil add organic matter such as compost, humus, well rotted manure sand‐ use only coarse builders’ sand not fine play sand 3. Size the garden o Storm water calculation 1 inch of rain on a 1000 square foot roof yields 623 gallons of water multiply the footprint of your roof by .623 to find run off in gallons for a 1 inch rain storm calculate average annual run off by multiplying the above number by 42 which is the average yearly rainfall in this region o Size must make sense in your landscape!
4. Shape the garden o Bowl shaped bottom o Flat bottom 5. Site preparation and garden installation o Pennsylvania One Call System 8‐1‐1 or 1‐800‐242‐1776 It’s free and quick o Mark your design o Remove the turf o Dig out the garden o Amend the soil if necessary o Create the berm using the removed soil o Berm will be higher on the down slope side of the garden o Cover the berm to prevent erosion o Lay out the plants o Plant o Water the plants o Apply 2‐3 inches of mulch o Line any swales with rocks or stones 6. Plant selection o Multiple zones wet zone‐ deepest, wettest area middle zone‐ holds water but drains sooner transition zone‐ upper zone, closest to rest of yard berm‐ dry o Refer to PennState Extension plant list at http://extension.psu.edu/gardening/maescapes/rain‐ gardens/plants‐rain‐gardens o Match cultural requirements sun/shade moisture size at maturity o Four season interest such as berries, fruits, pods, etc. o Use native plants beauty ease of maintenance wildlife habitat and food source deep root zones 7. Maintenance o Moisture to help establish the garden o 1, 3, 5 Rule until the garden is established o Check the berm for stabilization o Check the mulch for flotation movement o Weed as necessary