Rain, during summer months, is usually a welcome assist when caring for a vegetable garden. But when there is too much of a good thing, a flooded garden can be devastating. Beyond the physical damage to plants and structures, floodwater can introduce biological and chemical contaminants, making produce consumption a concern.
Pesticides, heavy metals, petroleum products, and raw sewage or manure are contaminants that can be picked up from adjacent fields, lawns, or paved surfaces as water flows overland and then are introduced into a vegetable garden during flood events. These contaminants may carry with them harmful bacteria, parasites, and viruses that pose a serious risk to human health.
What follows are guidelines for handling garden produce and managing a garden following a flood event. Not all is lost, but special considerations are required to maintain human and garden health.
During a flood event
Due to the risk of soil compaction and exposure to contaminants, it is recommended that gardeners wait until flood waters recede before entering the garden.
What to do with exposed crops?
As heartbreaking as it may be, produce that has been directly exposed to flood waters should be discarded. The risk of contamination from floodwater exposure is too great. Root vegetables, soft produce, and produce with a hard rind, including melons and squash, are all included as produce recommended for disposal.
Exposed crops should be disposed of in a way that keeps them separate from unaffected crops. Composting contaminated plants is not recommended. Avoid cross-contamination by cleaning tools and clothing before moving from an affected area to an unaffected part of the garden.
Crops that did not come into direct contact with the flood waters can be evaluated on an individual basis. Error on the side of caution. If flood water could have splashed onto produce, it is recommended that the produce be discarded. Flood waters may carry heavy metals that are deposited into garden soil. Garden plants growing in contaminated soil may absorb the toxins, thereby posing a risk to human health if those plant parts are consumed.
Replanting a garden
Vegetable gardens that have been flooded can be replanted. Over time, the process of soil drying and exposure to sun decreases the threat of biological contaminants. Precise time frame recommendations for a safety interval from the time of flood to replanting is not yet known and is impacted by a variety of environmental factors. The USDA recommends determining the source of the flood water to assess the potential introduced contaminants, sampling previously flooded soils to analyze for concerning microorganisms, turning the soil to encourage drying, and waiting 30 - 60 days to replant if biological contaminants are the primary concern. Chemical contaminants may remain in the soil for much longer, additional testing and mitigation may be required.
Alternatives to replanting
In areas that are prone to flooding or have experience a flood event that has created concern for the production of edible crops, alternative options exist.
Growing in containers or raised beds may be a temporary or long-term solution to remedy a flood-prone garden. Short-season vegetables (leafy greens, carrots, beets, radish, or herbs) can be planted to recover some of what was lost.
In gardens waiting for the recommended 30–60-day replanting interval, a cover crop may be desirable. Using a cover crop can help manage weeds while a garden rests. An annual, winter-killed cover crop is recommended for the home garden. Recommended species include tillage radish, buckwheat, cowpea, or oats.
Good Growing Fact of the Week: Flood water, as defined by the Food and Drug Administration, is “flowing or overflowing of a field with water outside a grower’s control”. This is differentiated from pooled water because flood water is likely to contain contaminants while pooling water is “not reasonably likely to cause contamination of the edible portions of fresh produce”.
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MEET THE AUTHOR
Emily Swihart is a horticulture educator with University of Illinois Extension, serving Henry, Mercer, Rock Island, and Stark counties since 2021. Emily provides horticulture programming with an emphasis on the home gardener, the urban forest, native plant ecosystems, and landscape design. Additional responsibilities include supporting local county Master Gardener and Master Naturalist volunteers - providing training, continuing education, advanced training, and their involvement in seasonal events and community outreach programs.