KC Gardens

Flooding and wet soils issues

Petunia in waterlogged soil

Tip of the Week

I know, from a personal story that many of us in the metro area are dealing with the results of the heavy rainfall over the past week. Living in an area that received about 5 inches of rain in less than two hours, the yard was a soaking, squishy mess. Unfortunately my basement carpet also was standing in water as a result of the downpour. But that is another story.

Waterlogged soils push out oxygen that plant roots need to survive. Every living cell in a plant must have oxygen or it dies. Some plants have mechanisms to provide oxygen to the roots, even under saturated conditions, but most vegetables and flowers do not. The longer these plants are subjected to saturated soils, the more likely damage will occur. Usually, as long as water drains within 24 hours, the impact on plant health is minimal. However, shallow, stagnant water under hot, sunny conditions can literally cook plants, reducing survival time to as little as a few hours.

VEGETABLES Vegetable are safe to eat from a garden that has been flooded. Standing water should not cause a safety problem as long as the above ground portions of the plant remain healthy. Do not use produce from plants that have yellowed. Also, using produce flooded with water contaminated with sewage (lagoon) or animal manure can be dangerous. The safest approach is to discard garden crops that have been in contact with such water. Certainly, leafy vegetables should always be discarded.

However, you can eat tomatoes, peppers, eggplants, sweet corn, squash, cucumbers, and similar vegetables that develop after the waters have subsided as long as the fruit is not cracked or soft. Always wash vegetables thoroughly before eating.

LAWNS Lawns under the cool conditions of early spring often can survive several days of flooding. However, during hot, sunny conditions, with shallow, stagnant water, lawns may be damaged quickly, sometimes in a few hours. This situation often occurs when shallow depressions in a lawn allow water to pool. Note such areas and fill in with additional soil once the waters have subsided.

TREES Trees differ markedly in their ability to withstand flooding. Some trees have mechanisms in place to provide oxygen to the roots of plants with water-saturated soils, and others do not. However, most trees will maintain health if floodwaters recede in seven days or less. It also helps if water is flowing rather than stagnant because flowing water contains more oxygen. If the roots of sensitive trees are flooded for long periods of time, damage will occur, including leaf drop, iron chlorosis, leaf curl, branch dieback and, in some cases, tree death.

Another danger of flooding is the deposition of sediment. An additional layer of silt 3 inches or more can also restrict oxygen to the roots. If possible, remove deep layers of sediment as soon as conditions permit. This is especially important for small or recently transplanted trees. Try to avoid additional stress to the trees this growing season. Ironically, one of the most important practices is to water trees if the weather turns dry; flooding damages roots, making the root system less efficient in making use of available soil water. Timely watering is vital to a tree’s recovery. Also, diligently remove dead or dying branches that may serve as an entry point for disease organisms or insect pests.

Fortunately most of us at this time are not experiencing the wrath of long-term flooding issues. We are mainly dealing with saturated soils. In this case, the main issue is the health of the root system and its ability to cope with the depleted oxygen. This is why many recommend the use of organic matter to help improve drainage and increased oxygen levels in the soil.

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