Plants and saturated soils

Ken Johnson

With all of the rain we’ve been having recently, many of our soils become saturated and in some areas flooded. When it comes to plants, too much water can cause as many problems as not enough.

Despite being in the ground, plant roots require oxygen for growth and respiration. When soils become saturated or flooded, it will reduce the amount of oxygen in the soil. The age/growth stage of the plant will affect how long a plant can tolerate these conditions; younger, smaller plants are more susceptible than most older, larger plants. Different species of plants are also more tolerant of flooded conditions, as well. Plants such as bald cypress and red maple are more tolerant of waterlogged soils than plants such as redbud, yews and fruit trees.

Plants will react to waterlogged soils in different ways. Symptoms can develop relatively quickly in annuals but may take a year or so to develop in woody plants. Symptoms of plants that are suffering from being in waterlogged soils include yellowing or browning of leaves, curling leaves that often point down, leaf wilt and drop. New leaves may also be reduced in size and trees may develop early fall color and suffer from dieback. In extreme cases, plants may begin to decline and eventually die. In all cases, stressed plants are more susceptible to attack by insects and diseases.

When it comes to fruits and vegetables, it’s best to be cautious when it comes to harvesting. Depending on from where the floodwaters came, produce can be contaminated (sewage, pollutants, etc.). If your garden flooded solely because of the rain, food is likely fine to consume (like always, make sure to clean produce before consuming it). If, however, floodwaters came from elsewhere (streams, roads, etc.), assume that the water is contaminated. Any fruits and vegetables that were ready for harvest at the time of flooding should not be consumed due to the potential of contamination. These contaminants will also be in the soil, so produce that comes in contact with the soil (including rain splash from soil) should not be consumed from the garden for at least 90 days.

There are several things that we can do to help plants that have been adversely affected by waterlogged soils. First, remove any dead, damaged or diseased branches. It may be helpful to rake mulch back temporarily to allow soils to dry more quickly. Since the root system of plants is often reduced (due to roots being killed), they will have a hard time keeping up with the water requirements of the plant. Therefore, if we encounter extended dry periods, provide plants with at least one inch of water a week. Finally, avoid fertilizing trees and shrubs for at least a year if they have been damaged due to flooding.

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