Tips for your yard and garden after heavy rains or flooding

Here are some tips for your lawn and garden after heavy rains or flooding from Louisiana State University Ag Center and other sources:.

Hurricanes and heavy rains can create excessively wet soil. If combined with high temperatures it can create stressful, and potentially deadly, conditions for bedding plants, perennials, vegetables, shrubs and even trees. 

When the soil is saturated with water, pore spaces in the soil that normally hold air are filled with water. Since the roots of plants get the oxygen they need from the air in those spaces, the roots can literally drown when soils stay waterlogged for an extended period. A sick root system leads to a sick plant. 

Wet conditions also encourage fungus organisms in the soil to attack the roots or crown of a plant and cause rot. The crown is the area where the stem of a plant enters the soil. These disease organisms can cause dieback or severe damage or even kill plants. Once infection occurs, little can be done to help a plant. Plants with succulent stems, those that like lower temperatures and those that prefer drier, well-drained soils are particularly susceptible.

Here are some tips for gardens affected by heavy rains:

1) Under saturated conditions, mulch should be pulled back from around plants or removed from beds entirely. This will allow evaporation to help the soil dry faster.

2) You can help plants that were affected by wet soils or root rot by aerating the soil in the root zone. Using a garden fork, drive the tines straight down into the soil about 8 inches and pull straight out in numerous places around the shrubs. Do not dig with the fork, but make as many holes as seems practical. This technique provides air to the roots and encourages the soil to dry faster. A metal rod or wooden dowel could also be used to make the holes.

3) Pests such as snails and slugs, which chew holes in leaves and flowers of many plants, thrive and reproduce rapidly during rainy weather. Try not to let their populations get out of control. If you have toads in your garden, that's great because they feed on slugs. You can place a bowl up to its rim in the ground and fill it half full of beer to attract and drown many snails and slugs or remove them by hand and dispose of them humanely.

4) Heavy rains over an extended period will leach available nutrients from the soil in the landscape. This is especially true of nitrogen and potassium but not so much for phosphorous. Give your plants a chance to recover from the saturated soils, and fertilize if needed if they do not improve. Do not fertilize hardy trees, shrubs and lawns after August, even after heavy rains. Late fertilization can make them less winter hardy. Do consider fertilizing bedding plants and vegetable gardens, if needed. Dried blood meal can add nitrogen to soil while rock potash can supply potassium.

5) Do not consume any vegetables that may have been touched by floodwater. There may be contaminants in the water. In general, fruits and vegetables which were immature at the time of flooding should be safe to eat by the time they are ready to harvest.

6) Some fruits and vegetables are more susceptible than others to bacterial contamination.

1. Leafy vegetables such as lettuce, cabbage, mustard, kale, collards, spinach, swiss chard, celery, and fleshy vegetables and berry fruits such as tomatoes, summer squash, strawberries and peppers are highly susceptible to bacterial contamination. Silt and other contaminants may be imbedded in the leaves, petioles, stems or other natural openings of fleshy structures and can be difficult to remove.
2. Root, bulb and tuber crops such as beets, carrots, radishes, turnips, onions and potatoes are less susceptible to bacterial contamination. Disinfect these vegetables, peel and cook them thoroughly before eating.
3. Produce with a protected fruit or impervious outer skin such as peas, melons, eggplant, sweet corn or winter squash should be washed and disinfected before the outer shell, skin or husk is removed. Then shell, peel or husk the produce and cook it if possible.

7) For additional safety, disinfect produce and cook it before eating.

8) Gardeners should take extra precautions to use good personal-hygiene when working in gardens that may have been flooded. Wash hands before and after gardening. Leave garden shoes at the door, and change clothing after working in a flooded garden. Avoid direct contact with flood waters, including the soil, as much as possible. Young children can be at a high risk for flood related contaminants. If a garden plot has been flooded, consider either not having young children in the garden with you or take precautions to utilize good personal hygienic practices.

9) Newly planted seeds and transplants may not survive even short-term flooding, and seeds may have washed away. Resist the urge to replant immediately; give the soil a chance to dry out first. Working wet soil will have long-lasting effects of soil compaction.

10) Many snakes are left homeless after a flood. They may seek food and shelter in debris caused by the flood or yard cleanup. Watch where you put your hands and feet when removing or cleaning debris. More information about local snakes.

11) Heavy rains can result in excessive breeding of mosquitoes, resulting in the possibility of disease being carried by the insects. Remove excess water from birdbaths, flowerpots, tires, buckets and other containers to minimize the breeding of mosquitoes.

12) Bees, wasps, and hornets may have had their nests disturbed by excessive wind and rain. The insects can become very aggressive. Before beginning clean up, survey the site to see if bees, wasps, or hornets are hovering in the area. Take necessary precautions to avoid these insects.

In addition to the obvious damage to plants, there are more long-term effects to soils, which have been flooded for extended periods. Soil microorganisms that require oxygen may be killed and those that survive without oxygen take over, which in turn affects availability of nutrients for plant use. The soil structure itself may be physically harmed due to compaction of soil particles.

It will be difficult to know the full effect of the heavy rains in the area until things begin to dry out. And then, of course, a lot will depend on what future stresses the weather may bring to our landscapes.

For more information contact your local Extension office:  

Cooperative Extension Services

• Virginia Cooperative Extension
• Home and Garden Information Center - Maryland Cooperative Extension
• Cooperative Extension Service – Washington, DC

or these sources, which I used in this articles:

Sources: Flooded Lawns and Gardens, LSU Ag Center

Flooded Gardens, (pdf file) South Dakota Cooperative Extension

After the Flood: Garden and Landscape Plants, Purdue Extension

Preventing Disease and Illness in a Flood – Fairfax County