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How to build a rain garden

By: Matt Grocoff , Contributing Writer
In: Green Renovations, Garden And Lawncare

Rain gardens are an ideal solution for many problems. Cities are overburdened with the high cost of maintaining storm drains and cleaning up after flood events. Our neighborhoods have destroyed native plant habitats for insects, birds, and other animals that are vital for human food production and survival. We've paved so much of our land that water simply does not flow the way the original ecology intended. Rain gardens can restore ecological water flow, mitigate flooding, help clean our water, and restore habitat that encourages biodiversity. And of course, they are beautiful and easy to maintain.

Here's how to build your own rain garden.

Find a suitable location

Rain gardens should be placed where than can easily capture rainwater that would otherwise run into storm drains. They should not be placed too close to your home. Here's some tips from the North Carolina Cooperative Extension on where to place a rain garden:

  • The garden should not be within 10 feet of the house foundation
  • Gardens should be located at least 25 feet from a septic system drainfield
  • Gardens should not be placed within 25 feet of a well head
  • Make sure to avoid underground utility lines
  • The best location for the garden will be in partial to full sun
  • Rain gardens should be constructed where the water table is at least 2' below the surface of the soil. If you hit the water table when constructing your rain garden, consider turning it into a wetland garden.

Make sure you've got good drainage

Some heavy clay or other dense soils may not provide enough drainage for a rain garden. First do a drainage test. Here's the steps:

  • Dig a small hole (enough to hold about one gallon)
  • Fill the hole completely with water
  • Check back in 24 hours. If the water has not drained in 24 hours, then your soil is not permeable and you should consider another location

Size your garden

A good ballpark is to size it about 30% of the square footage of the drainage area. For example, if you've got a 1,000sf roof area that you're draining into the garden, the garden would be about 300sf.

Here's a helpful Sizing Chart from NCCE https://www.bae.ncsu.edu/topic/raingarden/sizing.htm

Choose only native plants

Native plants are those that have adapted over thousands or even millions of years to your climate zone. They have also co-evolved with the many native animal and insect species. Planting only native plants will encourage biodiversity and resilience and usually don't have to be watered (no one was there to water them as they evolved before humans arrived). Importantly, native plants often have very, very deep root systems

Start Digging

Typical rain gardens are between 100 - 300 square feet. For determining how deep your rain garden should be, how to keep it level, and how to plant it, check out the Rain Garden Manual link at the bottom.

Plant your plants

If you've chosen the right plants that are native to your area, you will be guaranteed to have a beautiful, easy to maintain garden. However, you'll need to give it some time. Frankly, it's going to look pretty lame for the first couple years. But, your patience will be rewarded with more butterflies, birds, and natural beauty than you could have imagined.

Resources:

Rain Garden Manual: http://dnr.wi.gov/topic/shorelandzoning/documents/rgmanual.pdf

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