It’s June and its raining (again). Perhaps you have water in your basement, a washed out hillside, or just some soggy areas where your grass keeps getting killed. In any case, even if it is not flooding, rain can be a problem. Read on to find out how a rain garden might help.
What rain does after it falls from the sky
The ways we use our land have changed a lot in the last 200 years. Most of our forests, wetlands, and prairies have been replaced with houses, farms, businesses, parking lots and streets. These changes have changed how water behaves after it falls from the sky.
Water typically does two things after it rains. It moves across the land or it filters down into the soil to become groundwater. Water that flows across the land usually reaches our rivers, lakes, and oceans.
As water flows it carries with it sediments and pollutants that would have removed by slow infiltration into the soil. These can seriously harm ponds, streams, and groundwater resources.
Water Infiltrates at different rates
Infiltration is when water seeps into the soil and recharges our aquifers. Many aquifers are being drained quicker then they are being refilled.
Forests have less runoff because leaves and trees slow down the rain before it hits the ground. This gives the plant root’s time to absorb water and time for the water to soak into the ground.
When land is paved or cleared for buildings and the vegetation is removed there is no longer any vegetation to slow down the rain before it hits the ground. If the ground is covered with concrete or asphalt, no water can soak into the soil. Instead, the water runs over the surface, often causing flooding and erosion.
So how can we help the water infiltrate into the soil instead of running across it.
Adding Plants can help
Plantings can be used to get water to infiltrate into the ground where it belongs.
One simple way is to plant shade trees that will intercept the rain as it falls and slow it down before it reaches the ground.
Another way is with a rain garden.
I won’t get too technical here but there are specific details that are needed to create a successful rain garden. It’s not planting a crabapple with some daylily in a ditch like some people (including plenty of landscapers that should know better) would have you believe.
In it’s simplest description, a rain garden is a shallow depression that is planted with deep-rooted native plants that are adapted to seasonal flooding.
A rain garden should be located near a water runoff source like a downspout or sump pump. It can therefore capture the rainwater runoff and stop the water from running off. It should be at least 10′ away (preferably more) from your houses foundation.
Like any other garden, sunlight and soil types also matter. Rain gardens in Full Sun tend to be easiest to be successful with. This part shade “sump pump” garden is in the process of being built.
Not all the plants need to be ones that like water, the soil (I almost said dirt!) that I excavated out to make the depression makes a higher and drier place for plants like this Penstemon digitalis.
A Full Sun Rain Garden Plan
While I will have to wait for the rain to stop long enough to finish planting my “sump pump” garden, here is an design for proper sized rain garden in Full Sun I did earlier this year.
The plants heights are given at the end of the plant labels. Remember the planting is in a depression so the plants on the edges will be planted higher than the ones in the middle.
The New England Aster I would use today is probably the cultivar ‘Vibrant Dome’, although I might switch it out for a dwarf Joe Pye Weed like Little Joe (Eupatorium dubium ‘Little Joe’ PP16122).
Everything else except the Heavy Metal Switchgrass would probably be straight native species and not cultivars.