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How to Design and Care for a Rain Garden

A beautiful way to prevent flooding from excessive rainwater…

The best way to describe the weather in British Columbia lately is unpredictable — with near-record amounts of rain one year, and severe drought the next. And oddly enough, both situations are made worse by the same problem… large expanses of land whose ability to soak up rainwater has been compromised.

Landscapes that rely heavily on asphalt, concrete and other impervious surfaces, including lawns, have a serious impact on their ability to soak up rainwater. This creates two problems — flooding and erosion due to excessive runoff and land that’s unable to absorb enough water and nutrients to sustain plant growth, particularly during a drought. 

Fortunately, there are ways to lessen this impact in a way that is both sustainable and beautiful… by designing and installing a rain garden.

back yard with garden with mulch and perennials

What is a rain garden?

A rain garden is a landscape feature designed to collect rainwater that runs off your roof, lawn and driveway and other non-porous surfaces. They’re built by creating a shallow depression and filling it with a special soil mix designed for optimal drainage and water filtration, then planted with grasses and flowering perennials that tolerate drought, but are not afraid to get their feet wet! 

What are the benefits of a rain garden?

As stated above, the primary benefit of a rain garden is to prevent flooding associated with groundwater runoff, but they also have a number of other benefits too.

  • Manage stormwater — Rain gardens reduce the impact excess water has on local waterways, reducing the chance they’ll overflow and create mass flooding.
  • Cost-effective — Rain gardens are a natural way to manage stormwater runoff and are inexpensive when compared to traditional methods such as storm drains.
  • Reduce pollutants — The plants and soil used in creating a rain garden act as a filter, reducing the number of pollutants entering the water system.
  • Supports biodiversity — By creating a habitat for native plants and providing food and shelter for butterflies, songbirds and other wildlife, rain gardens support biodiversity and are eco-friendly.
  • Low maintenance — Because they help retain water and contain hardy plants, rain gardens are low maintenance. 
back yard with stone path a garden with mulch and perennials flowers

How to design a rain garden

Properly designed rain gardens help reduce flooding by holding on to excess rainwater, slowly releasing it over time. They complement any style of landscape and can be built to any size, based on available space, your property’s needs and personal preferences. Here are a few tips for designing yours.

  • Choose the right location — Your rain garden should be at least ten feet away from your home to avoid water damage. Make sure it’s not near a septic system or well and is properly graded — at bare minimum 1% — so the water flows away from your home. 
  • Determine its size — Make sure you have enough space for your rain garden and that it’s large enough to handle the amount of water you expect. This can be determined by the size of your roof and driveway as well as the average amount of rainfall for your area.
  • Prepare the soil — The soil in your rain garden needs to be well-draining and able to support the types of plants you choose. The optimal soil composition for a rain garden is a mixture of sand, compost, and loam. It's also important to ensure the soil is well-aerated, with plenty of space between the soil particles for water to move through. This can be achieved by tilling the soil before planting, or by adding organic matter such as leaf litter or wood chips to the top layer of soil.
  • Choose the right plants — Choose native plants,  including wildflowers, perennials, and ornamental grasses, that are adapted to the local climate and can tolerate both wet and dry conditions. Also, consider bloom time when selecting perennials to ensure your garden is full of beautiful colour throughout the year. 
  • Create your rain garden — Start with a man-made depression designed to collect rain runoff, then fill it with gravel or small rocks, soil mix, rain garden plants and mulch. 
a garden with mulch and perennials flowers

How to care for a rain garden

Caring for a rain garden is similar to caring for any garden, except the emphasis is on maintaining proper water flow and drainage in addition to plant health. Here are some tips to keep your rain garden healthy and functioning properly. 

  • Mulch your garden — Adding a layer of organic mulch to your garden helps it retain moisture, suppresses weeds, and provides the nutrients needed for plant growth.
  • Remove weeds — Just like any garden, it’s important to remove weeds from your rain garden to keep it looking tidy and prevent invasive species from taking over.
  • Monitor water levels — Make sure your rain garden is draining properly and there is no standing water. If there is a drainage issue, check the soil composition and slope of the garden and adjust if necessary. If this is an ongoing problem, you may need to consider installing an underdrain to help with drainage.
  • Get your soil tested — A soil test determines the pH and nutrient levels of your soil, helping you identify any deficiencies. Adding compost on a regular basis can provide nutrients for the plants and improve soil quality, reducing the need for chemical solutions.
  • Inspect for damage — Regularly inspect the rain garden for damage, such as erosion or damage to the berm, to help prevent further damage. Make the necessary repairs or alterations to keep it functioning properly.
garden with mulch, perennials flowers and flagstones

Interested in a rain garden for your property?

A rain garden can be a great way to manage stormwater runoff and support local biodiversity. By carefully selecting plants, designing the garden for maximum water absorption, and maintaining it properly, rain gardens can be a sustainable and beautiful addition to any landscape.

If you’d like help designing and building a rain garden — or any garden — for your yard, reach out to us. Our horticulturists will be happy to speak with you about your project and help you create a stunning and functional garden. 

Written by  Matt Vandenberg