The Ins and Outs of Rain Gardens

Jennifer Malka | Sept 2021

We at TABC have heard so many of those in our communities express their desires to start greening their homes and properties but say they don’t have the money for large interventions at the moment.  So here is a small, affordable green design project to consider: plant a rain garden. 

What is a rain garden?

A rain garden is very similar to a regular garden, only it is planted on top of a bed of purposefully layered mulch, well drained soil, sand, and gravel. The garden is typically slightly depressed and acts like a basin, capturing water during a large rain event and allowing it to slowly filter back into the water table. 

Why plant a rain garden? 

Rain gardens have many benefits, some of which include:

• Reduce flooding:  rain gardens are able to store a large amount of water run off from nearby roofs, driveways and the hardscape elements and then slowly releases into the water table below. 
• Reduce pollution in the local waterway:  the root systems and layering of soils helps to filter a significant portion of pollutants from run-off before it is returned to the water table.
• Increase Biodiversity: Rain gardens encourage the planting of a variety of beautiful native plants. 
• Encourage pollinators: many of the plants best suited to rain gardens are also bee and pollinator friendly.  

How big are rain gardens? 

• A rule of thumb is 1/10th the size of the area you wish to mitigate.  For example, your house has a 600 square foot roof, half of that drains towards the location of your rain garden, you’d want your rain garden to be about 30 square feet.

How much does a rain garden cost to install?

• A rain garden doesn’t cost much more than installing a regular garden.  A DIY garden installation could cost you as little as $3-$5 per square foot. 

What should I plant in my rain garden?

• Native plant species do best in rain gardens as they are adapted to our weather conditions and require little watering and maintenance. The TRCA has a great list on their website, including Milkweed, black eyed susans, prairie smoke, and more.  Your local, knowledgeable garden centre can assist you as well. 

There is a fantastic not for profit, community lead organization based in Toronto’s east end called Rain Gardens United. Since winning the Toronto Foundation’s 2015 Vital innovation grant, they have been busily working on creating an entire network of rain gardens.   Images for this post were all taken from their website, go take a deeper look: https://www.raingardensunited.com/events

Want to learn more about a rain garden and other ways to “green’ your home – Book a chat with one of our experts in affordable green design at The Architect Builders Collaborative.