Designing a Rain Garden for Minnesota: A Twin Cities Homeowner's Guide

A rain garden is a low spot in your yard, planted with water-tolerant species, that catches runoff from your roof, driveway, or hardscape. Done right, it stops basement seepage, reduces lawn flooding, supports pollinators, and looks great. Here's how Twin Cities homeowners actually build one that works.

Where to put a rain garden

The ideal spot:

• At least 10 feet from your foundation — closer and you risk water seeping into the basement.
• Downhill from your downspouts or driveway, so water naturally flows there.
• In an area that gets at least 4 hours of sun for full bloom display.
• Away from septic systems and large tree roots.

How big should it be?

A general rule for Minnesota: the rain garden should be roughly 20–30% of the surface area draining into it. So if your roof slope drains 500 sq ft of shingle, your rain garden needs to be 100–150 sq ft.

Don't overthink this — a slightly undersized rain garden still works, it just overflows during big storms. Plan to grade an overflow path toward your lawn or another drainage feature.

Soil prep — the critical step

Most Twin Cities yards are heavy clay, which holds water too well for a rain garden. The point of a rain garden is to infiltrate water (let it soak in within 24–48 hours), not to be a permanent pond.

Excavate the basin 18–24 inches deep, then backfill with a 50/50 mix of native soil and coarse sand or compost. This creates the loose, well-draining "rain garden mix" that lets water pass through quickly.

The 3 zones of a rain garden

1. Zone 1 (deepest, wettest): Plants that can sit in standing water for days. Native sedges, Blue Flag Iris, Cardinal Flower.
2. Zone 2 (sloped sides): Plants that tolerate periodic flooding. Red Twig Dogwood, Bee Balm, Joe Pye Weed.
3. Zone 3 (top edge, dries out fast): Native upland species. Little Bluestem, Black-Eyed Susan, Wild Bergamot.

Plants we trust for Minnesota rain gardens

• Eastern Larch (Tamarack) — native conifer that thrives in wet sites
• Red Twig Dogwood — handles flooding, year-round interest
• Swamp Milkweed — monarch host, loves wet feet
• Blue Flag Iris — native, survives standing water
• Joe Pye Weed — tall, pollinator magnet
• Cardinal Flower — bright red, hummingbird magnet
• Native sedges (Pennsylvania Sedge, Tussock Sedge)

Browse our full Rain Garden & Wet Clay collection.

The 5 mistakes Twin Cities homeowners make

1. Putting it too close to the house. 10 ft minimum, more is better.
2. Skipping the soil amendment. Native clay won't infiltrate fast enough.
3. Using non-native ornamentals. They die when conditions get too wet or too dry.
4. Forgetting the overflow. Big storms WILL overwhelm a rain garden — plan where the extra water goes.
5. Letting it dry out year one. New plants still need supplemental water for the first growing season, even in a rain garden.