Where should I put a rain garden on my lot?

Place your rain garden in a natural low spot that collects runoff, at least 3 metres from your foundation and 15 metres from your septic system (if applicable) — ideally where water already tends to pool after a heavy rain.

The goal of a rain garden is to capture stormwater runoff from hard surfaces like your roof, driveway, or lawn and let it slowly infiltrate into the soil rather than running off into storm drains or neighbouring properties. The best location is one that receives water naturally but doesn't already stay wet for days at a time — you want a spot that drains within 24-48 hours of a rainfall.

Start by watching your yard during a heavy rain. Where does water flow? Where does it collect? That natural drainage path is your starting point. A gentle slope leading into a shallow depression is ideal. You want enough grade to direct water toward the garden (1-5% slope works well), but not so steep that water rushes through too fast to infiltrate. In New Brunswick's clay-heavy soils — common in the Fredericton area and Saint John River valley — you may need to amend the soil with compost and coarse sand to improve infiltration rates, since clay can hold water too long and become anaerobic.

Placement rules to follow:

Keep the rain garden at least 3 metres from your foundation to protect your basement — this is especially important in NB where frost depth reaches 1.2-1.5 metres and saturated soil near foundations causes real problems. Stay 15 metres from any well or septic system. Avoid placing it directly over buried utilities (call before you dig — New Brunswick has a free locate service). Also avoid areas under large trees, where roots compete and shade prevents the moisture-loving plants from thriving as intended.

For NB's climate specifically, size matters more than people realize. Our spring melt combined with April and May rain events can send a lot of water across a frozen or saturated lawn all at once. A properly sized rain garden should handle runoff from a 25mm rainfall event — for a typical 1,000 sq ft roof section draining to one downspout, you're looking at a garden roughly 100-150 sq ft in area and 15-30cm deep. Shallow and wide is better than deep and narrow.

Plant selection is critical for NB's Zone 4-5 winters. Good native choices include swamp milkweed, blue flag iris, cardinal flower, Joe-Pye weed, and native sedges — all of which tolerate both wet feet after rain and dry periods between storms. Avoid non-native ornamentals that won't handle our freeze-thaw cycles or periodic flooding.

Practical first steps: Grab a garden hose and trace where your downspouts discharge, then follow that water path across your yard. Mark the low point. Do a simple percolation test — dig a 30cm hole, fill it with water, and see how long it takes to drain. If it's gone in under 24 hours, you've got a workable spot.

A rain garden is very DIY-friendly for design and planting, but if your lot has complex grading, drainage issues affecting your foundation, or you're near a watercourse, it's worth having a landscaper assess the grading first. New Brunswick Landscaping can match you with a local landscaper who can evaluate your specific lot and soil conditions — the matching service is completely free.