Yes of course, it rains on every garden, but does that mean every garden functions as a rain garden? Read on and learn what you can do to make a functioning rain garden in your yard.
In urban areas, rain falls on land that has 30-50% impervious surfaces. The polluted run-off is collected by storm sewers and piped directly into streams. After heavy rain, urban streams can’t hold all that water, and this can lead to erosion and flooding. Worse yet, water in storm sewers may get polluted by contamination from old leaky sanitary sewer pipes.
The purpose of rain gardens is to slowly soak the rainwater into the ground (the soil) where it is filtered and stored before eventually draining into the streams.
Can a typical turf grass yard do this? The answer is NO! The soil under lawn is often compacted and turf grass has shallow roots. Only little rainwater is stored in those typical “green carpets”. It ends up in storm sewers quickly. Lawn chemicals end up in run-off further polluting water.
What can be done?
There are many different resources on how to build rain gardens, but many seem complicated and costly, requiring major excavations of a yard. But every little bit helps, and you can start small and expand over the years. The key is to know about the “ingredients” that make a healthy functioning rain garden.
It all starts with healthy soil! When homes and buildings are constructed, the organic top layer of the soil is often removed. The more dense and hard lower soil layers become the top. They are often clay in Columbus, and they are further compacted by the construction equipment. The result is often rock hard and lifeless. It can’t store water and it doesn’t grow plants. Healthy soil is crumbly and porous. Only 50-60% of it is solid matter, the remaining space is filled with water and air. It has a large amount of organic matter, i.e. carbon and nutrients, and many critters live in that underground space eating and digesting organic matter.
Knowing this can get you started. Step 1 is to aerate and decompact the soil in your yard. This doesn’t have to be a large area all at once. You can start by digging a small area. Then add organic matter. You can simply leave the leaves that fall from your trees, and you can collect and compost your kitchen scraps. If you want to take it a step further, you can add saw dust manure or other organic material.
Next, you’ll want to let nature help you, while you help nature. Native Ohio perennial plants grow very deep roots. These plants will initially grow in the upper soil layer you created by digging and adding organic matter, but then they can “dig” their roots into the deeper soil layers. They’ll break up these denser layers as the plants go through their growing cycles. Each year about 25% of the roots die off adding organic matter. This and regrowth of new roots will progressively improve deeper and deeper soil layers. This healthy soil can store and filter large amounts of water, slowly recharging groundwater, and preventing run-off, thus reducing water pollution.
Of course, the plants and flowers growing on the top have many benefits also. They are beautiful and diverse, they can be selected to bloom from spring to fall, their nectar and pollen will feed pollinator insects, their seeds will feed birds, and the dense foliage provides shelter and nesting space for many creatures above and below ground.