We’ve past the first day of fall and the rainy weather has returned. If your yard is plagued with drainage problems this time of year, a rain garden may be the perfect solution to your drainage woes. By routing your drain systems and downspouts to a rain garden, you can move excess water on your property to a specific holding area that allows water to be absorbed by plant roots and slowly infiltrate into the soil instead of allowing stormwater to run off site.
Building a Rain Garden
To create a rain garden, the native soil is excavated in a carefully chosen area to create a depression or pond like feature, then it is filled mostly with a special bio-retention soil mix which has a very high water holding capacity. You’ll want to consider placement and size to make sure that it won’t be too close to buildings or other water sensitive areas in case of overflow and it’s large enough to contain the water that’s being routed to it. It’s important that throughout excavation, soil amendment, and maintenance, that the soils don’t get compacted to ensure proper drainage. When larger storms inevitably come through, having an overflow drain is crucial for when the holding capacity of the rain garden gets overwhelmed. After excavation and the bio-retention soil mix is brought in, the rain garden feature can be planted.
Planting a Rain Garden
Rain gardens have 3 main zones. Zone 1 is going to be the deepest/wettest area, Zone 2 are the side slopes that may get wet and may have some standing water occasionally, and Zone 3 is the perimeter area/driest area typically. The bottom of the rain garden (Zone 1) is planted with species that are tolerant of periodic emersion (our favorite is our native Carex obnupta). The sides of the rain garden (Zone 2) are planted with plants that are suitable to the amount of water they will receive by how close to the ponding mark they will be (progressively less tolerant of soggy soils as they reach the outskirts of the feature). Zone 3 is planted with ones that prefer drier conditions and can even handle some drought. Native plants can be great for rain gardens as they’re already use to our climate and rainfall patterns and can handle periods of drought in the summertime. You can also use pollinator friendly plants to really maximize the use of your rain garden. Here are few of our favorite rain garden plants categorized by Zone.
Zone 1 Plants
Carex obnupta spreads quickly to form a lush, green mat. Our favorite!
Blechnum spicant has glossy, crinkled leaves with a tidy appearance and are great for shady rain gardens
Cornus sericea ‘Kelseyi’ provides spring blooms and red winter stem color. Cornus sericea ‘Flaviramea’ provides yellow winter stem color.
Zone 2 Plants
Whether you’re looking for height or groundcover in this zone, Mahonia provides evergreen, year round interest. Flowers attract hummingbirds.
Deschampsia cespitosa has grass-like foliage that can reach up to 5 feet tall depending on variety. Deer resistant and pollinator friendly.
Gaultheria shallon has thick, evergreen leaves and small pinkish, white flowers in spring followed by edible black fruit which attracts various wildlife.
Zone 3 Plants
Physocarpus has deciduous foliage that comes in shades or deep burgundy to brilliant gold with cream to pink flowers in summer. Peeling bark provides winter interest. Range of sizes available depending on variety.
Vaccinium ovatum has glossy, evergreen leaves and bell-shaped white flowers in spring followed by juicy berries. Attracts pollinators and other wildlife. Good for adding height and part shade to full shade sites.
Arbutus unedo ‘Compacta’ can be grown as a large, evergreen shrub or trimmed up as a small tree. It’s covered in white flowers in spring followed by strawberry-like fruit. Both drought tolerant and deer resistant.
Maintaining a Rain Garden
While storm rains will water plants in the rain garden area periodically, it doesn’t mean you’re completely off the hook for watering. For the first 2-3 years after planting, your plants (whether they’re in the rain garden or other parts of your garden), will need to be watered deeply and regularly. This allows their root systems to grow deeper and become well-established. After that 3-year establishment period, your plants will need minimal to no extra water, but you’ll want to keep an eye on them during longer periods of drought. Mulching once a year will help keep weeds at bay and conserves water during dryer, hotter spells. As plants grow and take up more space, you’ll be able to reduce the amount of mulch you use. Instead of throwing them away, fall leaves are great to use as mulch along with arborist chips. Both provide nutrients to the soil. You’ll also want to keep your inflow and outflow locations clear of debris so water can flow where it needs to. Rocks and cobble are great for protecting these areas from debris. If you have a bermed rain garden, you’ll want to check for settling or bare patches and keep a watch out for any erosion around the rain garden and correct as needed with rocks/drain cobble to help spread out the flow of water. It’s important to keep fertilizers, pesticides, etc out of your rain garden so that when it overflows, you’re not sending anything unwanted to other parts of your property or off site.
Rain gardens are very dynamic elements that take more time to establish than other drainage solutions but in time can often outperform many other options. They can be designed to be beautiful, useful garden features that allow your garden to thrive and be enjoyed even in the wettest times of the year. If you have a wet site that could use our help and you’re ready to get started or if you just have a question, you can contact us here.
~Colleen & Kryssie
