When installing a rain garden, the most important thing to keep in mind is where water will be entering the rain garden, and where water will be leaving the rain garden.
Water will most likely enter your rain garden from the downspouts you identified earlier.
It may require some trenching and corrugated pipe to re-route the downspouts to your garden area.
When trenching, remember to use a level – to avoid standing water in the pipes, the level of the pipes must always be traveling downhill.
As you reach the garden area, try and have the bottom of the pipes come in as high as possible with respect to the surrounding landscape – best case scenario, the bottom of the pipe is level with the top of the garden. This is called an inlet.
Place stones around the inlet to prevent erosion.
If you are building a rain garden on a slope, you may be required to build a berm on the back side of the garden.This will allow you to store as much water as possible in your garden.
If you build a berm, be sure to compact it using a tamper to avoid erosion and water loss!
In the event of a major storm, the rain garden WILL overflow, and it’s important that we control where that water is leaving the garden.
This will be your outlet.
The most important thing to remember is that your outlet must be below the level of your inlet.
In doing so, water will be guaranteed to overflow from the garden where you want it to, and not back up into your pipes.
To prevent erosion, you must stabilize your outlet.
For the outlet, place a capstone at least 1ft wide to form a stable weir. On the back side, place small, loose rocks to channel the water.
These can be purchased at your local hardware store.
Now that your inlet and outlet are set, it’s time to make sure your garden is 10 inches deep across its entire area.
To do this, we will use a tool called a line level. You will also need two stakes and a strong string – all of which can be purchased at your local hardware store.
Place a stake at one end of the garden, tie the string around it with a strong knot, and run it to a stake at the other end.
Make sure the string is taut, and place the line level.
Adjust the string at either stake until the bubble reads level.
Next, take your tape measure and check the garden depth at various points along the garden.
A shorter depth means you need to dig that portion deeper.
A longer depth may require more soil.
Once your garden is level, it’s time to plant it!
Place the plants you chose in the design phase in the garden, but don’t plant them too deep. The next step will be adding mulch, and the top of the mulch should be no higher than the crown of the plants.
When mulching, it’s recommended that you use triple-shredded hardwood mulch.
This type of mulch tends to settle better and not float away and clog your outlet during major rain storms.
With the inlet, outlet, plants, and mulch, you have a working rain garden!
Keep in mind that there will be some additional maintenance required.
For example, it’s important to weed your garden every season.
This will keep your plants happy and healthy.
You may be required to water your garden, especially during the drier months.
If it hasn’t rained at least an inch in the last week, go ahead and water.
Every few years, it’s recommended that you replace the mulch in the garden.
And finally, it’s very important that you NEVER fertilize your garden. Excess nutrients from fertilizer can cause algal blooms downstream! Learn how to install a cistern!
ECWA has created a maintenance guide to help you get the most out of this Creek Smart® addition to your property. View or download the Rain Garden Maintenance Guide