Flooded Vegetable Garden Sites and Food Safety Considerations

The devastating, historic floods in Nebraska and Iowa will leave their mark on the region for many years to come. Loss of life, homes, livelihoods, and infrastructure are of major concern, but many people who rely on their gardens or vegetable plots for food or income may also have some concerns for the upcoming growing season. The garden season may not have started yet in the heartland, but as the waters recede and clean-up efforts continue, there’s one area of concern that many may not have thought of: the safety of garden produce from flooded areas.

It is difficult to know exactly what is in the flood waters that ravage communities, especially since the water is flowing in places where it was not expected to be.  Aside from the standard level of pathogens or contaminants that may be in the water, there could be additional contamination from sewage systems, manure storage, industrial chemical storage, pesticide or fertilizer storage, and more.  Due to the all the unknowns in regards to flood water, gardeners and produce growers should exercise caution in the upcoming growing season. Even if the water is just pooling in place and not visibly coming from a stream or if you think the area up-stream is free of contamination there is still a need to minimize risk from flooding.

Food Safety Risks- a waiting game

For the most part, the biggest risk from flooding in garden areas is the potential of food borne illness from pathogens such as E. coliSalmonella, and others. Food safety hazards are a concern for all individuals, but are especially worrisome for those with compromised immune systems, the elderly, pregnant women and young children.

While the current flooding occurred before most vegetable fields were planted, there should be a waiting period between when the flood waters recede from the garden/field and when produce is harvested to minimize human pathogen risks. Plants may be sown or planted in the garden during the time period, but produce should not be harvested until after the waiting-period has ended. Exposure to the solar energy from the sun can help reduce pathogens exposed to the environment, but keep in mind that some pathogens can persist in the soil for several years.

In this instance, the recommendation comes from food safety best practices for farmers relating to the application of manure, which are based on standards from the National Organic Program.  Research shows that the health risk from non-composted manure is higher than the risk from flood waters, so this recommendation is usually considered a good starting point for flood garden safety decision.

The recommendation depends on whether or not the crop comes in contact with the soil.  For crops that do not have direct contact with the soil, such as tomatoes, peppers, beans, etc. the waiting period between flooding and harvest should be at least 90 days. For crops that do have direct contact with the soil, such as lettuce and leafy greens, squash/pumpkins, and root crops such as potatoes and carrots the waiting period should be at least 120 days.  If the crops that don’t typically make contact with the soil are allowed to make contact, like tomatoes that aren’t staked, the 120 day recommendation should be followed.   

Therefore, planting fast-growing early spring crops, especially those that are in direct contact with the soil like leafy greens, is not recommended for areas where flooding occurred in the Nebraska March floods since they be harvested sooner than four months after flood waters recede. But planting warm-season crops like tomatoes should be fine, since they wouldn’t be harvested until after the end of the waiting period.

Harvests from perennial food plants, such as rhubarb, asparagus, strawberries, fruit trees, bushes, or brambles should also be subject to the waiting period.  Any edible portions maturing before the end of the waiting period should be removed and discarded.

Food Safety for Actively Growing Gardens

In cases where flooding occurs in actively growing gardens and fields, any produce that is touched by flood water should be removed and destroyed.  There is no method of preparation that can reduce or remove the hazards associated with direct contact of flood waters on produce.

While the safest practice would be to discard all plants and produce from a flooded garden, there are some steps that home gardeners can take to salvage produce from areas of the garden that were not covered with flood water.  The following criteria should be met before salvaging produce:

  • the plants were in an area of the garden that was not covered with flood water,
  • the edible parts of plants  will ripen/mature at least a few weeks after the flood 
  • AND were not touched by splashing water.

Any edible portion of the plant that is mature at the time of flooding or within a few weeks should be discarded.  The following recommendations are for salvaging immature produce affected by floodwaters in home gardens.  For produce farmers affected by flooding in crop fields, food safety recommendations state that no produce should be harvested from flooded fields and sold (until after the waiting period has passed), even from areas of the garden that were not covered with flood water. The risk and liability is too high. In many instances, farm insurance or federal assistance can help cover crop losses.

First, discard any crop plants that are consumed raw, such as leafy greens. There is no way to properly clean the produce and remove all of the contamination and there is no way to know if any flood waters splashed on the non-submerged parts.  Any soft fruits, such as berries or tomatoes should be discarded if they cannot be cooked or peeled or if you think there could be chemical contamination.

If the edible portion of the plant was not touched by flood water, you may be able to harvest it and cook it  for consumption.  Thorough cooking can destroy aerobic food borne pathogens, but does not destroy chemical or industrial contaminants. If you feel that there could be such contamination in the water, all produce should be discarded and plants destroyed.

Prior to cooking, any produce that is salvaged from flooded garden areas should be completely washed with cold tap water. Inspect for any damage, cracks, or damage and discard any produce that appears damaged – breaks in the surface of the produce This is a good recommendation for any garden, but it is especially important the season following a flood. Do not use soap, however you can soak produce in a dilute bleach (2 Tbsp per gallon of water) for two minutes then rinse again with cold tap water.

Potential contamination can also depend on how mature the plant is at the time of flooding and what part of the plant is covered by floodwater. For example, if a tomato plant is covered by floodwater but that tomato plant doesn’t currently have tomatoes on it, future tomatoes growing on that plant could be considered safe after the 90 day waiting period has passed.  One good approach would be to remove all flowers and fruits after the flood and allow new ones to develop.

And remember, when in doubt, don’t risk it. If you are unsure about the safety about any garden produce, remove and destroy all plants.

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Resources and further reading:

Safely Using Produce from Flooded Gardens -Univ. of Wisconsin Extension

Flooded Garden – What’s Safe to Eat? – Nebraska Extension


John Porter
Urban Agriculture Program Coordinator at Nebraska Extension
John Porter is the urban agriculture extension educator for the Omaha metro area and statewide program leader for the Horticulture, Landscape, and Environmental Systems team at Nebraska Extension. He specializes in urban agriculture and horticulture, especially in the areas of vegetable and fruit production for home gardens, urban farms, and edible landscaping.
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