Typical size of a rain garden

Rain gardens are typically 100-300 sq ft.

Rain gardens are typically 100-300 sq ft.

The question many customers have is “What size should my rain garden be?”  The quick answer is that usually rain gardens are between 100 square feet and 300 square feet.

  • Smaller than 100 square feet?  It’s possible, of course, but such a small garden will have very little variety of plants.
  • Large than 300 feet?  Always possible, of course, but that’s a lot of digging, and becomes much more expensive at that point.

Here’s a handy way of finding out the best size for your rain garden:

  • Find the “size factor” (use the data sets below) which works for your type of soil and how deep the garden is
  • Multiply that by the drainage area (the size you are thinking for the rain garden).
  • Your answer?  If it’s more than 300 square feet, it’s recommended that you divide it into two or more rain gardens

Here’s the sets of data to use:

Rain gardens LESS THAN thirty feet from the downspout:

Sandy soil?

  • 3-5 nches deep:  0.19
  • 6-7 inches deep:  0.15
  • 8 inches deep:  0.08

Silty soil?

  • 3-5 nches deep:  0.34
  • 6-7 inches deep:  0.25
  • 8 inches deep:  0.16

Clay-type soil?

  • 3-5 nches deep:  0.43
  • 6-7 inches deep:  0.32
  • 8 inches deep:  0.20

Rain gardens MORE THAN 30 feet from the downspout:

  • Sandy soil?  0.03
  • Silty soil?  0.06
  • Clay-type soil?  0.10

We hope this blogpost helps!

Minnesota Rain Gardens
1223 Dayton Avenue
Saint Paul, MN 55104


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