Rain Gardens

What is a rain garden?

A rain garden is a bowl-shaped garden that collects, absorbs and filters storm water. Rain is captured at a chosen point (such as a driveway or roof downspouts) and directed to the garden. As the water filters through the soil, plants and soil micro-organisms clean it. Rain gardens are built with soil mixes that allow water to soak in rapidly and support healthy plant growth.

A rain garden is a way to add beauty to your landscape while helping to protect local streams, lakes and groundwater. Hard surfaces such as roads, driveways, patios and roofs don’t allow rain water to soak into the soil. Instead, the water runs off, causing flooding, scouring stream banks and carrying pollutants such as pesticides, fertilizers and motor oil.

Scientists working to restore Puget Sound name storm water as one of the major contributors to the decline of the Sound. According to the US Environmental Protection Agency, storm water runoff is the leading threat to the nation’s estuaries and the third-largest problem facing lakes.


Things to think about when considering a rain garden:

Where to Site the Rain Garden

Rain gardens should be kept a minimum of 10 feet from any building foundation. They are not appropriate over septic drain fields or shallow utilities.

Soil Type

Not all soils will be suitable for a rain garden. Fast-draining soils are best. A simple soil particle test can help determine how quickly your soil will drain . Amending or replacing the soil may improve drainage rates. Soil type and drainage will also be a factor in determining rain garden size.

What are your collection points?

You could use a roof, driveway, neighbor’s lawn, etc. This will help determine the actual size of your rain garden.


How big will the rain garden need to be? How much area is draining to the rain garden? How much space is available? How much water from the drainage area will the rain garden hold? How quickly does water drain from the area?

References & Resources

The following references will provide more detail on benefits and construction of a rain garden. Or call In Harmony to assist you with your design at 425-486-2180.

Angies List