How to Handle Excessive Rain in the Garden

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How to Handle Excessive Rain in the Garden

How to Handle Rain: Go with the Flow

The arrival of spring means it is finally time to get back in the garden, but for a lot of the US the soggy conditions are making this impossible. The combination of spring rains and the melting of this winter’s substantial snow has led to a lot of flooding and standing water, which means that for most of us, our soil is too muddy to work with right now. In these soggy months, take this opportunity to evaluate the movement of water through your property and design a garden that goes with the flow rather than against it.

Don’t let your yard become a bog; manage rainwater wisely with this 3-step process:

First, observe your property during rain storms and get a feel for how water is flowing through it now.

Second, deal with your lawn’s storm runoff and boggy areas by creating a rain garden.

Third, improve your land’s dry areas by creating swales and/or xeriscaping.

Get the Lay of the Land

There is no one right answer for how to make the most of rainfall. The answer is always “it depends.” It depends on how much slope there is on your property. It depends how compacted or how well-draining your soil is. It depends how deep your local water table is. It depends how much rain you get. It depends how much water your gutters or driveway are dumping on your lawn. Every situation is unique, so you have to pay careful attention to your yard and find the problem areas that you want to address.

Smart garden designers always evaluate the area and come up with ways to work with the existing water flow rather than imposing their own vision. If you try to add a rain garden or a swale where it doesn’t belong, you might end up with an unattractive mud pit. So be sure to figure out the natural flow of water on your property and develop your plan from there.

The first thing you will probably notice is any areas of standing water. These are usually dips or low-lying areas of the landscape that retain water. These are potential sites for rain gardens or at least good sites for water-loving plants. Next, look at areas that are more dried out, where plant growth is sparse. This often happens on the slopes of hills, where all the water quickly drains after rain. Here you can try to improve water retention with a swale. Xeric plants, which tend to originate from desert-like conditions, are also great for these areas because they are highly drought tolerant. These plants can replace water-thirsty lawns with beautiful perennials that, most years, won’t need a drop from you.

You need to determine two other things about your land that might not be immediately obvious:

1. How good the drainage is, and

2. How high the local water table is. You can determine both things with a very simple test: just go out to your back yard and start digging a hole. Make this hole about 1’x1’x1′.

If you hit water, or if the hole begins to slowly fill up, then your water table is obviously very high, and this means it can be extremely difficult to achieve good drainage in this spot. In this case, you could either try and rise above the water table with raised garden beds, or you could simply plant water-loving plants that don’t mind wet feet, like Japanese water iris , rodgersia, calla lily, weigela, astilbe, lobelia, and Joe Pye weed.

If, on the other hand, you get to a good depth without hitting water, then there is hope. Your standing water is probably just a drainage problem. Next do a drainage test: Fill your foot hole with water and then keep an eye on how long it takes to drain.  If it takes 4 hours or less (about 3 inches per hour), then your drainage is adequate for a rain garden or other planting. If a lot of water remains after 4 hours, then you need to improve the drainage.

My yard has that red clay that is prevalent in much of the South–good for staining your car, driveway, shoes, and carpet, but not great for growing plants. Digging the hole in a sandier spot gives it SOME amount of drainage–by the next morning (~12 hours later) the hole was drained. To grow anything here, we need to improve the drainage more and add a lot more organic matter: hence the necessity of my compost pile.

Other ways to improve soil drainage are by adding gravel, pipes, or tile underground and/or by conditioning your soil. Sometimes soil is just compacted, and needs to be worked with a spade or tiller to loosen it up and allow drainage. If the soil has a high clay content (like mine), then you should amend it with compost and/or sand. Another way to improve soil drainage is to add in some Garden Gypsum, which gathers the clay into pellets and allows water and air to flow through.