We at the MsK Nursery at the Kruckeberg Botanic Garden have been having more conversations about how to build rain gardens lately. Urbanization, reduction of the tree canopy and increased impervious surfaces all equal high-impact rainfalls. It doesn’t take much to see your street turn into a stream or the basement into a bog. Rain gardens are fantastic because they intercept precipitation and can prevent pollutants washing into drains connected to Puget Sound and will help minimize overflows during storms.
What can you do?
- Plant a tree. A mature tree can hold an amazing amount of water by just providing surface area to detain the rainfall. Water is then released at a much slower rate to allow for steady infiltration into the ground. Stand under the Giant Sequoia (Sequoiadendron giganteum) one time when it rains – you will stay completely dry.
- Permeable paving. Permeable pavers, such as the type used in our new parking area, work quite well. The water penetrates through the spaces rather than creating a surface flow. Try installing pavers or broken concrete for patios and walkways. With a bit off moss or a creeping groundcover, this can be really attractive, or go with gravel if you like a tidy look.
- Love your wetland. Have a wet spot in the yard? Lucky you! There are so many fantastic and gorgeous plants that like moist soils. You can enhance this area into a beautiful garden feature. We aren’t fortunate enough to have a naturally occurring wetland at KBG, but we have built a few bathtub bogs, bogs in buckets and simulated seeps to grow some of these moisture-loving plants.
Let’s build a rain garden!
A shallow depression placed in an existing low spot or in line with a downspout will hold—and most importantly—filter pollutants from stormwater. Parking strips are great locations too. Even though our new permeable parking lot is working really well, we at KBG can’t resist the opportunity to build our own rain garden. There is a bit of planning involved – you have to consider drainage and some engineering aspects, but there are many workshops and seminars offered to help to design your rain garden. Some neighborhoods are even offering rebates to assist homeowners.
Most rain gardens have three zones ranging from wet to dry, creating an opportunity for a vast array of species and looks. I keep picturing a wet alpine meadow with native Rudbeckia, Potentilla, Geranium, Arnica, and fun sedges and rushes. A colleague recently designed a rain garden to honor his client’s football team – think Asters and Erigeron. Another friend created the most orderly and geometric rain garden I have ever seen. It is gorgeous and abstract.
Want more information on rain gardens and low impact design?
Stewardship Partners and WSU’s 12,000 Rain Garden campaign
Get the Raingarden Handbook For Western Washington Homeowners
Is your home eligible for a raingarden rebate?
Low Impact Development and research