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Excessive Rainfall and Its Effects on the Garden
By Kristen Pullen
Are you tired of the rain yet? It’s safe to say that most of us here in southeastern Pennsylvania are saying, “Enough already!” The total rainfall amounts for the past few months in Philadelphia have broken the previously held records, with June totaling 10.49 inches and July totaling 13 inches. Over this wet season it has been a common occurrence for me to go out and see standing water in my backyard and in the plantings around my neighborhood. Plants can tolerate short periods of saturated soil, but extended times of sogginess are stressful. The reason for this is that an increased amount of water in the soil means there is less air in the soil. The soil in your garden has tiny air pockets between the fine particles where oxygen can be found. The water fills up these holes and, when not draining properly, remains in these spaces between the soil particles. This lack of oxygen causes roots to drown and can eventually lead to the death of a plant. So what does too much water mean for your plants? Recently we’ve received some calls about plant health that directly relate to the extremely wet season we’ve been having. Some of the symptoms of a saturated plant include:
- Yellowing and defoliation of the leaves. The foliage of a plant is usually the first place you will see noticeable symptoms. Look for yellowing or decay between the leaf veins. Sometimes you will see dark areas on the midrib. These damaged leaves will eventually die and drop off.
- Wilting when the soil is wet. Your plant will look like it needs a drink and show wilting symptoms typically seen in the heat of the summer. This is caused by the roots drowning. The root system can no longer take up water to supply the rest of the plant, causing shoots and canes to die back or bark to peel off sections of the plant.
- Root rot. The lack of air in the soil has caused the roots to drown. A sample of the root ball will usually appear black or brown and sometimes have a pungent, rotting smell. Pull lightly on one of the roots and see if the outer covering easily slips off. If this occurs then you have root rot.
- Poor vigor. This applies to the overall poor performance of a plant in saturated conditions. It may experience stunted growth, flowers that are smaller than normal, a decreased flower show, sections of the plant dying, loss of the glossy appearance of the foliage, and leaf or flower buds that open and die quickly after.
In addition to these symptoms, persistent wet and humid conditions are ideal for other diseases such as black spot and mildews. Powdery mildew shown below.
We know we can’t control the weather, so what can be done for our gardens this year? This is a good time to reassess your garden beds and the locations you have chosen for your plants. Are there certain areas that have stayed soggy and areas you notice that have better drainage? Make note of these locations and remove plants from poor drainage areas to a dryer location. If possible, gardening in raised beds will ensure better drainage than planting directly into the ground. Try to choose plants that can tolerate higher levels of water if you wish to replant in soggy areas. Avoid walking on the soil around your plantings until the area has substantially dried out. Foot traffic on soggy soil will compact the ground and put added stress on the root systems. When it has dried out a bit, be sure to remove any dead or decaying plant material in your garden beds and trim off any remaining symptoms on your plants. Unfortunately, some plants won’t make it through these wet conditions or have already died as a result. Hopefully this season has given us some insight on better planting plans for next year. Here’s hoping for a more stable growing season next year!