What is a Rain Garden?

For those of us living in the Lower Mainland, it might be tempting to think that the whole province is a rain garden. But rain gardens are actually a resourceful way to improve drainage on your property. They also increase curb appeal while creating a visually appealing space for you and your family to enjoy.

Definition of a Rain Garden

A rain garden is a shallow depression or hole dug in malleable soil and then planted with a combination of deep-rooted native plants and grasses. Rain gardens are devised to conserve water and help alleviate the effects of pollution.

How Rain Gardens Work

Strategically placed rain gardens capture water from downspouts or hardscaped areas such as driveways and patios, keeping runoff out of the sewer system. Channeling water away from hard surfaces also helps prevent landscape erosion and concrete driveways and sidewalks from becoming pitted or cracked. After a significant rainfall, a rain garden fills with water, which then filters down into the soil. Designed to imitate forest ecosystems, it’s structured to hold water for 24 to 48 hours. To increase filtering efficiency, the soil of a rain garden is often lightly mixed with sand and other organic matter topped by an overlying layer of mulch.

Rain Garden Location

To function effectively within the microclimate of your property, integrate the rain garden into your existing landscape. Rain gardens should be located in the direction of runoff and low-lying areas where water tends to collect; be downhill, away from the foundation of the house; and situated in an area where the soil is absorbent. A rain garden thrives in a combination of sun and shade; ensure that part of the garden will be in the sun for several hours per day. Other suggestions for finding the right location for a rain garden are:

  • before digging, call BC One Call to make sure you won’t hit any underground wires, cables or pipes
  • avoid hitting the water table – when constructing the rain garden, dig where the water table is at least two feet below the surface
  • situate the garden a minimum of 10 feet from the foundation
  • when there’s a septic system, it should be located at least 25 feet from the drain field
  • when there’s a well, the garden should be placed at least 25 feet away from the wellhead

Rain Garden Design

Select a natural, low-maintenance style over more formal designs. When you choose native plants, they have already adapted to climatic conditions, so they don’t require edging, watering, fertilizing, etc. like a tradition, formal garden.

A rain garden is typically divided into three zones: the centre (zone 1 – standing water) for plants that like wet conditions; the middle (zone 2 – water begins filtering downward) for plants comfortable tolerating semi-wet conditions; and the outer edge (zone 3 – dry buffer area) for plants that are drought-resistant.

Carefully consider the size and corresponding shape of the rain garden. The right size-and-shape combination attracts the eye, creating a pleasing focal point. Popular profiles include the teardrop, kidney-shaped, the oval, and the S-curve.