How to design and build your rain garden

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