Rain Gardens

  • Rain gardens are vegetated, shallow, bowl-shaped landscape features that absorb runoff from roofs and driveways.

    Rain gardens fill with a few inches of water after a storm, then filter the water into the ground instead of to stormdrains. They naturally protect our water sources and look great.

    Resources 

    • Maintain a Rain Garden
    • Build a Rain Garden
    Maintain a Rain Garden

     Community rain garden FAQ

    Rain gardens are installed in Pleasant Valley and new Springwater Communities to support nature-friendly communities that use plants and soil to remove road pollutants such as oil, grease and chemicals before they reach local water bodies. These plants support local wildlife and the roots help water drain. In other words, rain gardens help soak up rain and pollution!

    • Who is responsible for maintaining the rain gardens in the right-of-way?

      Rain gardens located in the street or other green spaces within your neighborhood will be maintained by the City 2 – 4 times per year. This includes hand weeding, spot spraying with Rodeo (approved formula), removing leaves, sediment and debris, mulching, replacing dead plants and clearing inlets and outlets.

    • Can I help care for the street rain garden in front of my home? 

      Yes. The City has limited resources. You can help stretch our resources by:
      • Removing leaves and dirt build up at the inlets and outlets and placing in your yard debris container.
      • Lightly pruning rushes (leaving 8 inches of leaves above the soil) and hand weeding.
      • Planting non-invasive decorative flowers like daffodils or pacific coast irises. Keep in mind, we cannot guarantee plants will not get damaged or removed eventually to manage the rain garden over time. 
    • How do I care for the rain garden on my property? 

      The rain garden’s plants need minimal care, no fertilization and are drought tolerant once established. You may prune, if desired, at end of winter. Avoid using pesticides, if possible.

    • What about mosquitoes?  

      Rain gardens are designed to drain within 3-4 days, well before the required seven days mosquito larvae need to reach maturity. If you notice mosquito larvae in ponded water, rake or pour the water onto a drier area so they will suffocate.

    • Can I alter my rain garden? 

      Yes. Your home’s roof and drainage was planned to drain into your onsite rain garden, which has a perforated pipe connecting the overflow to the street.
      You are required to manage your roof water within your landscaping and can make design changes to your rain garden, as long as it still captures and filters the water through the soil on your property.

      Plants for sunny rain gardens
      Plants for shady rain gardens

    • Do I need a permit? 

      Changes to your rain garden design will require a permit only if it needs to alter the stormwater disposal point. Adding plants, rocks, or design features that do not alter the drainage design outlet location do not need a permit.

    • Is it okay for a person or contractor to pour anything into the rain garden? 

      No. Many of these things – construction waste, paint rinsate, car fluids, cleaning supplies, carpet cleaner, wash water, etc. – are likely to harm the plants and wildlife and can leave unattractive solids in the rain garden.  

      Best practice is to use a utility sink, toilet or tub to dispose of wastewater, where it will travel to the City’s wastewater treatment plant.

    If you see a spill or intentional dumping
    • Call 503-618-2626; after hours, 503-661-3906; or use My Gresham.
    Build a Rain Garden

    Steps to build a rain garden

    Plan

    • Contact the City to determine your soil, slope and available space is suitable for a rain garden.
    • Confirm your property is in an area of Gresham with well-drained soil on the GreshamView map.  Select Downspout Disconnection/Rain Garden Area in map layers.
    • Call 811 for for utility locates.  Confirm the location of existing utilities and avoid conflicts. Oregon Utility Notification Center
    • Ensure there is enough space between your property line and neighboring properties and sidewalks.
    • Test your soil drainage rate.

     Build 

    • Lay out your garden using stakes, rope, and other tools.
    • Excavate the soil.
    • Create an entry for water, an extended rain gutter or downspout.
    • Use a compost mix to blend into existing soil.
    • Provide rock-lined overflow.

     Plant 

    • Line your garden with weed barrier before planting.
    • Space plants for mature size, but consider planting densely in the ponding area.
    • Plant drought tolerant plants on the garden’s outer edge.
    • Use native plants. Native Oregon plants are adapted to local weather, pests and disease and don’t require fertilizers, pesticides or water once established.

    Maintain

    • Keep inlet and overflow clear of debris and well-protected rock.
    • Don’t use fertilizers, pesticides or herbicides.
    • Provide additional mulch as needed.
  • Rain Garden Plants

    • Red Elderberry (sun)
    • Pacific Ninebark (shade)
    • Dern fern (shade)
    • Oregon Iris (sun)
    • Camas (sun)
    • Bleeding Heart (shade)
    • Checkermallow (sun)
    • Sedge (sun) various species
    • Rush (shade) various species
    • Kinnikinnick (sun)
    • Oregon Fawn Lily (shade)
    • Vanilla leaf (shade)
    • Evergreen huckleberry (sun)
    • Red Columbine (sun)
    • Birch-leaved spirea (shade)
    • Red Osier Dogwood (shade)
    • Vine Maple (sun)
    • Dull Oregon Grape (shade)

    1 of 18
    • Tall, deciduous up to 20 feet; white flowers in spring, red berries in early summer. Plant in the bowl of the rain garden. Sambucus racemosa

    • Tall, deciduous shrub up to 12 feet with shredded bark and clusters of white flowers. Plant in bowl of rain garden where the most water will collect. Physocarpus capitatus

    • Medium evergreen 1-3 feet tall. Blechnum spicant

    • Medium plant up to 2 feet; purple blooms in spring, dark green blades. Iris tenax

    • Short perennial wildflower from bulb up to 2 feet; produces dazzling blue flowers with yellow centers. Plant along drier outer edges of garden. Camassia quamash

    • Short perennial wildflower up to 2 feet; feathery fern-like foliage and cascading pink heart-shaped flowers in spring through early summer. Full to partial shade; plant along drier edges of garden. Dicentra formosa

    • Short perennial wildflower up to 2 feet; showy clusters of pink flowers favored by butterflies. Plant along drier edges of garden. Sidalcea sp.

    • Medium clumped evergreen grass-like plants up to 3 feet. Tufted structure with foliage ranging from greens to bronze. Provides year-round garden interest; check for shade tolerance before purchase. Plant in bowl of garden. Carex sp.

    • Short, spreading shrub up to 8 inches. Low-growing evergreen groundcover with drooping pink flowers and red berries. Plant along drier outer edges of garden. Arctostaphylos uva-ursi

    • Short, perennial wildflower, up to 1 foot; produces nodding white flowers, frequently yellow at base of petals. Plant along drier edges of garden. Erythronium oregonum

    • Short, white spiked flower atop wide flat leaves spring to summer; fragrant dried-leaves. Achlys triphylla

    • Tall evergreen 4-8 feet with light pink flowers, spring to summer; edible; beautiful foliage with some fall color. Slow growing. Vaccinium ovatum

    • Short, perennial wildflower up to 3 feet, taller wildflower with multiple drooping red and yellow flowers. Prefers dappled sun; plant along drier outer edges of garden. Aquilegia Formosa

    • Medium deciduous shrub 3 feet x 2 feet; dark-green, shiny leaves, flat white flowers in summer; great for pollinators. Spiraea betulifolia var. lucida

    • Tall, deciduous shrub up to 15 feet. Does best in partial shade, reddish twigs create garden interest through the fall and winter, plant in bowl of garden. Cornus sericea

    • Tall, deciduous shrubby tree up to 25 feet; bright green leaves turn brilliant red in the fall, smooth green bark provides garden interest in winter. Plant in bowl of garden. Acer circinatum

    • Short, small shrub up to 2 feet; low-growing plant with shiny evergreen leaves, yellow flowers and purple berries. Plant around drier outer edges of garden. Mahonia nervosa