Planning Your Rain Garden
Creating a rain garden in your yard is a simple, cost-effective project.
Below you’ll find six simple steps to help you along:
Assess your site
- Take a look at your property and find out from where your source of water will be coming (a downspout, driveway, patio, or sidewalk).
- Your rain garden should be close to this source of runoff, but at least 10-20 feet from the foundation of your home.
- Be conscious of any trees on your site – we don’t want to disturb an already established root system.
- Call OUPS before you dig – (800)362-2764 – to avoid underground utilities.
- Consider an overflow – perhaps you will direct any overflow back into the downspout that is connected to the street.
- Also consider your mowing habits and how wide your mower is, especially if you usually hire someone to do the work. Be sure there is enough room for a mower to pass through whatever other landscaping is already in place next to your garden.
Know your soils
Dig an 8” deep test hole, and fill the hole with water. Check back after 24 hours and measure how far down the water has drained.
Sizing
- The depth that your test hole has drained will be the depth of your rain garden.
- Based on the depth of your garden, you will need to determine the length and width.
- Calculate how much drainage area will be directed into the garden (for example, square footage of the amount of rooftop draining into the downspout you will disconnect).
- Divide your drainage area by your depth.
Example: I have 240 sqft. of rooftop draining to a downspout I will disconnect. My test hole drained 4” in 24 hours. My rain garen will be 4″ deep. I then divide 240 by 4, and my rain garden will be 60 sqft.
(This calculation is from The Blue Thumb Guide to Raingardens by Rusty Schmidt, Dan Shaw, and David Dods, 2007.)
Get ready to dig!
- In order to start digging, outline the shape of your garden with marking spray, flags, or a garden hose.
- Remove the existing top layer of sod, and dig down to the depth you found in step 3.
- Till up the top couple inches of soil.
- Add a 2” layer of compost and mix into your existing soil.
- Grade the bottom of the garden evenly.
Plants
- Choosing your plants is just as important as sizing your garden correctly. They will be doing most of the work in your garden.
- Choose plants that are tolerant of flooding and also tolerant of drought (since it won’t be raining everyday, and your garden should drain in 24-48 hours).
- Consider color, bloom time, and height of the plants. A wide variety of colors and bloom time are available.
Also consider using native plants, as they are better suited to our soils, climate, and pollinators. Cultivars of natives also work well, as they may prove to be less aggressive and more compact. - Locate the plants in the garden according to their tolerance of water – the most water tolerant plants should be placed closest to where the water will enter the rain garden.
- After the plants have been planted, add a 2-3” layer of double shredded hardwood mulch to keep in moisture and keep out weeds.
Water/Maintain
Your rain garden will need to be watered throughout the first growing season. If you use native plants, they should take off and do well on their own after their first year.- The plants will fill in as the years go by, but applying mulch year after year is a good idea. Over time, less mulch will be required.
- Watch for gullies and erosion – a quick fix to an unanticipated path of water entering the garden is to place several cobble stones at that entry point to slow and spread the water.
- In the fall and spring, be sure to clear out any leaves that may have collected at the water entry point to your garden to be sure the flow of water is not restricted.
- Labeling your plants is a good idea, especially if you aren’t sure which ones are weeds when they come back in the spring or if you have friends or co-workers over to see your garden!
