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Prepare the Site

Your Rain Garden's Soil Must Be Able to Absorb Rain

Soils on developed land has been compacted by heavy construction equipment. You'll need to dig to a depth of two feet and loosen the soil. If the soil is too sandy or contains a lot of clay, you might want to replace it with a rain garden soil mix.

Easy Rain Garden Soil Mix

  • 50-60% sand
  • 20-30% topsoil
  • 20-30% compost
  • Mix well

How Much Soil Mix Do I Need For Replacement?

One cubic yard equals 27 cubic feet.  A rain garden that is 2 feet deep by 5 feet wide by 10 feet long (2 x 5 x 10 = 100) will need 100 cubic feet of replacement soil, or about 3.7 cubic yards.

How to Improve Your Soil

Adding compost or other organic matter is the best way to enrich your soil. A compost of decomposed yard waste like dead leaves and grass clippings is usually the best.

If you do not have your own compost, you can purchase it at garden centers and many other retail locations.

Define Your Borders

When it comes to shaping your rain garden, the sky's the limit. You might like a simple circle, square or rectangle.  But to give your rain garden a flowing border, begin by spraying an outline on the ground with nontoxic soccer field paint. Or use a garden hose to mark the shape of the border and dig next to the hose.

Dig In! Some Ideas to Make the "Hole Project" Easier

If you're digging your rain garden in your lawn, you will have to remove the turf. A sod cutter might make this job easier. You can use the turf you remove on another part of your lawn or compost it. 

If you are not replacing your soil, we recommend double-digging to a depth of two feet:

  • Remove the soil and pile it to the side.
  • Dig and loosen the earth in a new hole, and pile it loosely into the first hole.
  • Mix compost into the soil if you are doing soil improvements.
  • Repeat this process until the soil in the whole garden is prepared.
  • A great tool for this purpose is a digging fork.

 Adding a reservoir of gravel on the bottom of the bed, or tiles or an underdrain that lead to another area will keep your rain garden from becoming waterlogged.

The idea is to create a living sponge of soil, plants, roots and mulch, not a soggy bog.

How to Create a "Ponding" Area in Your Garden

Water entering your rain garden should spread out over a large flat area and soak into the soil. A dip or "ponding" area about six inches deep will make this happen.  You might have to remove a lot of soil.  When your ponding area is ready and the soil is nice and loose, it's time to plant!

Next: Why Native Plants?


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