Stormwater Planters

stormwater planter at EMSWCD

A stormwater planter is an easy and attractive way to manage and filter some of the rainwater coming off a roof or other impervious surface. Managing this water helps protects our urban streams and infrastructure, and reduces the load on them. Rainwater runoff enters the planter and is filtered through a layer of mulch, soil and sand before it overflows onto your lawn, landscaping, or into a rain garden. The water-loving rushes and sedges in the planter also absorb a lot of the water.

In a large rain storm, the planter is designed to overflow out of the overflow pipe. To ensure the treated water coming from the planter doesn’t damage the house foundation or overflow onto a neighbor’s property, the overflow outlet should be located a safe distance from property lines and house foundations.

The overflow outlet should be:

  • a minimum of 6 feet from a house with a basement
  • at least 2 ft from a house with a crawl space or slab foundation
  • at least 5 ft from any property line
  • at least 3 feet from a public sidewalk
Permits:

Check with your local jurisdiction to determine whether you need a permit to disconnect your downspout and direct it to a stormwater planter.

Maintenance:

Once the stormwater planter is built and set up, it will generally not require much maintenance! Runoff from the roof will provide water the plants need for much of the year. Here are two things you can do to keep your plants in good health, and able to absorb the most stormwater.

  • weed and mulch the planter as you would any landscaped area
  • water the plants during dry summer months
Planter Design: Notes, and a sample diagram with technical specifications

The diagram below is just one of many potential designs! Many factors should be considered when selecting a design or coming up with your own, such as the roof area the downspout covers. It is recommended that a plastic liner be used to line the trough before other components are installed.

diagram of a stock trough stormwater planter

Ideal Native Plants for a Stormwater Planter

Stormwater Planter – Plant List Latin name – Common name

Evergreen Groundcovers
Carex densa – Dense sedge
Carex stipata – Sawbeak sedge
Carex obnupta – Slough sedge
Deschampsia cespitosa – Tufted hairgrass
Juncus patens – Spreading rush
Flowering Accent Plants
Camassia quamash – Common camas
Mimulus cardinalis – Monkey Flower
Lupinus polyphylus – Large-leaved Lupine
Lupinus rivularis – Stream Lupine
Source: City of Portland, Vegetated Stormwater Facilities in the Public Right of Way, 2007

 

Design your own stormwater planter!

If you have questions on where to find designs, or whether a stormwater planter would work in your yard, email Kathy Shearin or call at (503) 935-5365.

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