Many of us have certainly been thrown a curve ball with the recent flooding.
I know three community gardens in our Extension district have gone totally underwater. So that brings the question how safe is the produce from gardens affected by flood water? The following information is from Extension resource material.
Because we do not know where precisely the flood water has been (in a lagoon, across an animal feeding facility, a sewage treatment plant, etc.), consuming produce that has been exposed to flood water is dangerous. The safest approach is to discard garden crops that have been in contact with such water.
When flooding contamination occurs, it is best to haul away plant materials.
As for replanting, it is recommended to allow time for contaminant levels to diminish in the soil 120 days is the recommended wait period.
What about standing water (not flood water) in the garden? Standing water should not cause a safety problem as long as the aboveground portions of the plant remain healthy. Do not use produce from plants that have yellowed.
Waterlogged soils have had the oxygen pushed out that 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 of our 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.
Flowers will usually survive at least 24 hours under flooded conditions. If water stands longer than 24 hours, plants may die outright, or the lack of oxygen may encourage root rot diseases. Raising the level of soil in flower beds, even by a few inches, can help avoid damage in the years that follow.
As for lawns, because of the cool conditions of early spring, turfgrasses often can survive several days of flooding. However, during hot, sunny conditions with shallow, stagnant water, lawns may be damaged quickly, sometimes within 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.
Grass plants may not be able to take up the nutrients needed to maintain a good green color when there is too much soil water and may have a yellowish hue. Fortunately, this chlorosis will correct itself when soils dry. Plants should regain their color with a return to drier weather.
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 7 days or less. It also helps if the water is flowing rather than stagnant because flowing water contains more oxygen. If the roots of sensitive trees are flooded for long periods, the 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 trees recovery. Also diligently remove dead or dying branches that may serve as an entry point for disease organisms or insect pests.
Flood-tolerant trees can survive one growing season under flooded conditions red maple, silver maple, pecan, hackberry, persimmon, white ash, green ash, sweetgum, sycamore, eastern cottonwood, pin oak, and bald cypress.
Trees moderately tolerant of flooding can survive 30 consecutive days under flooded conditions river birch, downy hawthorn, honeylocust, swamp white oak, southern red oak, bur oak, willow oak, and American elm.
