Rain gardens
Build one that is the right size,
and it will run itself.
A rain garden is a shallow planted basin that takes runoff from a roof or driveway and lets it soak in. The design is simple. Almost every failure traces back to one of three things: wrong size, wrong soil, or wrong place.
Runoff calculator
Catchment area and soil type in, runoff volume and required garden size out. Start here.
Percolation testing
How to measure your real infiltration rate with a shovel, a bucket, and an afternoon. In progress.
Plant selection by region
Species that tolerate both a 48-hour soak and a dry August. In progress.
The build sequence
- Measure the catchment. Roof footprint in square feet, per downspout.
- Test the soil where the garden will go, not somewhere convenient nearby.
- Size the basin from those two numbers. Calculator.
- Site it at least 10 ft from the foundation, off the leach field, out of the water table.
- Excavate and level. The basin floor must be flat, or the whole garden drains to one end.
- Build the inlet and the overflow. Every rain garden needs somewhere safe for water to go when the storm exceeds the design.
- Plant, mulch, and water through the first two summers. After that it is on its own.
The one rule. Size before you dig. Resizing a finished basin means moving the same soil twice.
About this section
Guides are being rebuilt and published progressively. The runoff calculator is live now. More on the project.