Rain gardens are quickly becoming a common element in residential landscapes. In fact, in many cities, new developments are required by code to install rain gardens. They’re a great way to add an environmentally-friendly feature to your yard while also performing a dirty job: managing stormwater runoff. They can also be an attractive and more affordable option to putting in a drywell.
The Issue with Stormwater Runoff
Stormwater runoff is the massive volume of water created during rain storms. Within urban landscapes, this runoff doesn’t have much chance to absorb into the ground. It flows over impervious surfaces like roofs, driveways, parking lots and streets and into the City’s stormwater system. Contaminants in the water accumulate from flowing over these surfaces and ultimately end up in our rivers, lakes and streams. This contaminates our waterways, endangers wildlife, and leads to costly municipal improvements in stormwater treatment structures.
The Environmental Impact
These contaminants can also include pesticides and fertilizers used on permeable surfaces like lawns and plant beds. When the fertilizers reach our waterways, they can decrease oxygen levels and result in algae blooms. The lack of oxygen results in a decline in fish populations.
How Rain Gardens Can Help
Rain gardens filter out these toxins by capturing the first flush of rain (the first inch or so of rainwater runoff) which usually contains the highest concentration of pollutants. Keeping this runoff onsite mimics the natural landscape that was once able to absorb and clean stormwater before we covered so much of it with hardscapes. The combination of plants and soil acts like a sponge and helps filter out and neutralize the pollutants.
Other Benefits of a Rain Garden
In addition to keeping polluted stormwater out of our waterways, keeping the runoff onsite has additional benefits:
- Can help solve flooding and drainage issues
- Recharges the ground water supply
- Provides habitat and food for wildlife
- Enhances the beauty of yards and the community
Keeping runoff onsite can also save money on your water bill. In the Portland area, you can receive a discount based on how many downspouts are disconnected from your house. A disconnected downspout provides a perfect opportunity to direct runoff into a rain garden or similar feature.
What to Plant in Your Rain Garden
It may come as a surprise that a lot of common plants will work in a rain garden. There are two key points to keep in mind when selecting plants: where in the swale they will be located and what kind of sun exposure the garden gets. Plants along the bottom of a rain garden will require the most specific consideration. In the PNW, these plants need to be able to tolerate both flooding in the winters and drought in the summers. A lot of natives fit this bill perfectly and are beneficial to pollinators.
Along the edge of the swale, a larger variety of plants can be considered. When selecting them, try to include ones that will offer winter interest as well. These can be evergreens or plants that have some structure, like seedheads or interesting branching.
Here are some preferred PNW plants that will work, depending on the situation:
Bottom of swale
- Asclepias – Butterfly Milkweed
- Carex – Sedge grass
- Hemerocallis – Daylily
- Lobelia – Cardinal Flower
- Physocarpus – Ninebark
- Rosa pisocarpa – Swamp Rose
- Salix – Willow
Edges of swale
- Achillea – Yarrow
- Echinacea – Coneflower
- Fragaria – Wild Strawberry
- Monarda – Bee Balm
- Rosa nutkana – Nootka Rose
Bottom of swale
- Acorus – Sweet Flag
- Adiantum – Maidenhair Fern
- Carex – Sedge
- Cornus sericea – Red Twigged Dogwood
- Dicentra – Bleeding Heart
- Juncus – Common Rush
- Mimulus – Monkey Flower
Edges of swale
- Aquilegia – Columbine
- Lysimachia nummularia – Creeping Jenny
- Polystichum munitum – Sword Fern
- Mahonia – Oregon Grape
- Philadelphus lewisii – Mock Orange
- Ribes – Flowering Currant
- Vaccinium ovatum – Evergreen Huckleberry
Incorporating Rain Gardens in Your Landscape
Some properties may have space constraints or other issues where a rain garden isn’t feasible. There are other options that safely capture runoff. Permeable pavers, flow-through planters, drywells, swales or dry creek beds all perform the same basic functionality of keeping runoff onsite and out of the stormwater system.
An individual rain garden may seem like a small thing, but collectively they produce substantial environmental benefits throughout the community. From a homeowner’s point of view, they can add a unique element of beauty to your landscape. They are usually planted with native flowers and grasses that can withstand both flooding and drought. They also promote environmental responsibility. When neighbors see a successful rain garden, they’ll want to add one too!
There are lots of resources online to create your own rain garden. Here is a good place to start, especially if you’re in the PNW. Hopefully, this will serve as inspiration to add your own!
Contact Blessing Landscapes today!
At Blessing Landscapes, we love to incorporate rain gardens into our designs. They are an elegant solution to mitigate stormwater, help support habitat, and they create a unique focal point in the garden. We can do all the work of installing them as well. Contact us today if you’d like to update your landscaping with one of these great features.