Rain garden

• Location: Decide on the location for the rain garden. To qualify for the RainWise Rebate Program, you must either have a downspout directing stormwater flow to the rain garden or have stormwater directed into a drainage way that allows stormwater to flow into the rain garden.
  • If possible, choose a low laying area on your property where everything drains naturally.
  • Please ensure your rain garden is 3 m away from building foundations and away from steep slopes or the top of a bank. 
  • If you are planning to place it near a road, consider slight setbacks.
  • Identify where the stormwater will enter the rain garden (inlet) and where the rainwater will overflow (outlet), when needed. 
• Size: To size your rain garden, you will need to know the area of your roof. Our RainWise rain garden sizing tool will help you play around with different sizes of rain gardens based upon the size of roof area (directly connected Impervious area). 
• Depth:  
  • A rain garden has a shallow depression, but deeper soil than a normal garden to provide more soil volume to soak up water. The soil depth can range from 250 mm to 450 mm in depth.
  • Plan for an even surface with a slope towards the outlet.

Materials required: Rain Garden Design, string, stakes, level, metre stick, measuring tape, lawn paint (optional), garden hose

• Review your Rain Garden Design.
• Measure out rain garden as per design, with lawn paint, stakes, string or garden hose along garden outline.

Use this opportunity to make any small changes to the rain garden shape. Keep in mind that major changes in location or shape of the rain garden may impact the planting plan and the function of the rain garden.

Materials required: edging spade, rototiller, shovels, wheelbarrow, tarp, string, stakes, level, metre stick, sod cutter (optional)

This is the most labour intensive task of building a rain garden. Having as many volunteers as possible to help will lighten the load and speed the process. 

• Use an edging spade to cut sod along outline of rain garden border that you have already painted or laid out with string or a garden hose.
  • Optional: Use sod cutter to cut, roll and remove sod from rain garden area, beginning along outside edge and moving in toward the centre in a circular pattern.
• Use a rototiller to break up sod (if not removed with sod cutter) and existing soil, within the interior of your rain garden layout.
• Use shovels and wheelbarrows to remove tilled soil. Continue until depth of raingarden is reached, as indicated in the Rain Garden Design you created in Step 1.
  • Optional: Soil can be temporarily placed on a nearby tarp if a trailer/truck is not yet available.
• Gently slope edges of soil up from base of rain garden to meet existing ground level. The rain garden should resemble a shallow bowl; the edges should be gradual, not steep.
• Use a rototiller to loosen soil (scarify) in base of rain garden to depth of 300 mm (12 in).
• If Rain Garden Design requires, berm the lower edge of the garden with soil removed when digging out the rain garden.
• Dispose of sod and excess soil in your green bin or at the Edmonton Waste Management Centre or an Eco Station. Paper bags to be used for the disposal of yard waste can be purchased at your local hardware store.

Materials required: shovel, erosion control blanket and seed (optional), sod (optional), washed rocks (optional)

• Create an outlet from the garden by digging a shallow channel in the berm, allowing water to overflow in the intended location indicated on the Rain Garden Design.
• Use string, level and stakes to check that outlet is the lowest point along outside edge of the garden.
• Reinforce the outlet to prevent erosion, using rocks, sod or seed and erosion blanket, as per the Rain Garden Design.
• If using rock, spread washed rock (e.g. 10-20 mm or a smaller angular rock) in a 150 mm (6 in) layer.

The rain garden outlet requires erosion protection since excess water leaving the garden will be concentrated at this location. Rocks or grass on the side of the berm meeting the existing lawn will slow the flow of water leaving the rain garden and protect the soil from eroding.

Materials required: topsoil, shovel, tamper, landscape rake, string, level, 8 ft 2x4 (optional)

• Fill rain garden with topsoil to design depth.
• Tamp down the soil by walking on it, soil should be compacted enough that deep footprints are not created.
• Install another 50 mm to 200 mm of soil (depending on depth of garden) and tamp down.
• Rake topsoil to create an even surface. Check that the surface does not have low areas by using a level and string or run a 2x4 level across the surface.

Sections of the garden that are lower than designed, will tend to pond water during large rain events. Remove mulch and fill area with soil, replace mulch. 

Materials required: garden spade, watering can, plants, gloves

• Place plants throughout garden at locations indicated on Rain Garden Design. Check out our list of native plants for ideas on what to plant. 
• Use garden spade to dig holes, to the depth indicated on the instructions that come with the plant.
• Use watering can to flood the bottom of each hole.
• Remove plants from pots, break up roots as needed, and install in holes, pressing down lightly to ensure top of plant soil matches rain garden soil. Leave enough space between the plants for the plants to mature and grow.
• Once all plants are installed, water garden well. Apply fertilizer for establishment, as needed.

To avoid having to thin plant material later, space shrubs and plants based on their expected mature size, according to your Rain Garden Design.

Materials required: shovel, landscape rake, mulch

• Scoop mulch into garden placing it into piles throughout.
• Spread the mulch evenly, up to 100 mm (4 in) deep, by lightly raking into place.

Mulch helps with water retention and discourages weed growth. Note: Do not use landscape fabric under the mulch as it will inhibit plant growth. 

Materials required: washed rock, shovel

• Place washed rock or larger rocks, 150 mm (6 in) deep, at inlet to garden from lawn or downspout, covering area indicated on Rain Garden Design. This reinforced inlet is to protect the rain garden from erosion and provide a location where sediment can drop out of the incoming water before entering the rain garden.
• Slope rock to direct water into the rain garden.

Placing rocks at the inlet slows the force of the water entering the garden, preventing erosion of the soil. Rocks also allow sediment and debris to drop out of the water before entering the garden in order to protect the garden soil from clogging.

Materials required: washed rock, shovel

• Identify downspout(s) to redirect to the rain garden.
• Cut downspout, connect extender and direct toward rain garden.
• Divert downspout extension around rain garden location until the rain garden has been planted, mulched and has an appropriate inlet.

Downspouts can be disconnected and directed into existing lawn or garden areas until the rain garden is complete. Do not direct downspout extension into unfinished rain garden.

Direct the disconnected downspout to the rain garden inlet. 

Congratulations! This is the final step in changing your yard area into a rain garden!

See our rain garden maintenance checklist for directions and tips.