seal  Purdue News

July 8, 2003

Recent rains cause 'flood' of garden and landscape concerns

WEST LAFAYETTE, Ind. – Recent storms and torrential rainfall have flooded gardens and landscapes, but a Purdue University expert has tips that can help homeowners cope with the aftermath.

Rosie Lerner, Purdue Cooperative Extension consumer horticulturist, said safety should be a concern for gardeners. Floodwater may be contaminated with raw sewage, making produce potentially dangerous. If the produce can be peeled, washed thoroughly and/or boiled, it poses minimal risks. Crops that are eaten uncooked, especially leafy crops such as spinach and lettuce, pose a greater risk of being contaminated. Lerner advises consumers not to eat raw produce that may have been contaminated.

Newly planted seeds and transplants may have been washed away with the rising water. Lerner said there is still time to replant, but cautions people to wait until the soil dries out to avoid soil compaction problems.

Lerner is unsure of what long-term effects the heavy rains will have on landscaping trees and shrubs. How much oxygen the plant has been deprived of will be the deciding factor.

Flooded soils push out oxygen, which can cause root systems to die. Plant tolerance to oxygen deprivation varies, Lerner said.

"The general thought is that most landscape plants can survive being submerged for about a week or so," she said.

If an extended lack of aeration to the roots occurs, it will result in root die-back. Above-ground symptoms include yellowing leaves, droopy foliage, dropping leaves and, eventually, dying branches.

Not only is there a chance the plant may die, but the root system may come under attack by root-rot organisms. Soil erosion and deposits of soil and silt also may damage the plant's root system.

In addition to soil movement, more long-term effects to the soil may be seen. Soil microorganisms that require oxygen and are found naturally in soil may be killed. Those that can survive without oxygen will then dominate and affect nutrient availability to plants.

Ultimately, only time will tell how much plants will be affected by the high water, Lerner said.

And once this water is gone, cleanup will need to be done. Trees with damaged limbs should be pruned or repaired.

"Branches that have lost leaves aren't necessarily dead," Lerner said. "Even though leaves may drop, there may be buds that will be able to re-leaf yet this summer."

To be sure that they will survive, check for visible green tissue.

For more information on flooding, plants and proper pruning practices for damaged trees, visit

Writer: Michelle Betz, (765) 494-8402,

Source: Rosie Lerner, (765) 494-1311,

Ag Communications: (765) 494-2722; Beth Forbes,;

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