Rain Garden Design Plan, 18x14 ft Basin, 9 Native Species (PDF Download)

A drawn, to-scale planting plan for an 18 ft x 14 ft rain garden basin. Nine species, eighteen plants, each one placed by how much standing water it will actually take.

A RAIN GARDEN IS THREE GROWING CONDITIONS IN ONE HOLE

That is the thing most plant lists miss.

The floor of the basin holds water for hours after a storm. The side slopes drain in minutes. The rim above the ponding line is often drier than the surrounding lawn, because water runs past it rather than into it.

Plant one list across all three and a third of it dies. This plan assigns every species a position - floor, slope or rim - and says which is which.

WHAT YOU GET (6-page PDF, instant download)

- The plan, drawn to scale, on a full page - circles are mature spread, nothing overlaps
- Plant schedule: 18 plants, 9 species, with quantity, mature size, light, spacing and basin position
- A USDA hardiness zone range on every plant, looked up individually
- What the plan assumes about your basin, including ponding depth and drain time
- The percolation test to run before you dig
- Installation sequence, and why you mark your real ponding line before following any drawing
- Where your overflow is legally allowed to go, with the case law
- Sources, cited

DO THE PERCOLATION TEST FIRST

Dig a hole a foot deep where you are thinking of putting it, fill it with water, let it drain, fill it again and time it. If the second fill has not gone in 24 to 48 hours, do not build a rain garden there.

Heavy clay frequently fails this test, and no plant list survives a basin that never empties.

THE PLANT THAT CATCHES PEOPLE OUT

Cardinal flower. Its soil should never be allowed to dry out. It belongs on the basin floor and nowhere else. It is regularly sold as a general perennial, planted on a slope, dies in its first dry August, and the buyer concludes rain gardens do not work.

WHERE IT APPLIES

Drawn from USDA Zones 7b-8a. Seven of the nine species run from Zone 3, 4 or 5 through Zone 9, so the plant list travels a long way. The schedule tells you which is narrowest.

The basin arithmetic does NOT travel and is not in here. Sizing depends on your rainfall, your roof or driveway area, and how fast your soil takes water. Use your own state or county Extension guide for the hole. Use this for what goes in it.

WHAT THIS IS NOT

Not a stormwater design. Not an engineered drawing. Not a sizing calculation. Not a substitute for drainage that discharges legally off your property. Anything in a regulated stream buffer, wetland, floodplain, or any permitted stormwater device goes to a licensed professional engineer.

Call 811 before you dig.

I am a licensed North Carolina landscape contractor (CL.1872) and NDS Certified Drainage Contractor. I am not a professional engineer.

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