Flooding: Before & After
Restoring Vital Services — Flood damage to ornamental plants in the home landscape
Flood damage to ornamental plants from rising water generally is not extensive. Most of the damage that occurs results from water standing about the root system for several days. If flood waters recede in two to three days, generally no damage is done to trees and shrubs.
However, if floods occur at the time of year when the temperatures are very high, the plants may be subjected to scald and death of the root system. This doesn't happen very often because most floods occur in mild weather. An exception would be rising water during a hurricane in coastal areas.
No special precautions can be taken for plants because it's not practical and in fact, is injurious to plants to dig them up and put them in containers to keep them from being flooded. Usually, other property commands a higher priority when it comes to flood protection.
After flood water has receded, wash the silt or mud from the leaves. This does not have to be done immediately and, in many instances, if the silt or debris is allowed to dry on the leaves, much of it will fall from the plant leaf surfaces as it dries. What is left can be hosed down from the leaves.
Plants standing in water for several days are put under stress, so it is important that they be kept free of insect and disease pests during the subsequent growing season. Nor should they be allowed to undergo stress during any dry periods following the flood.
Some of the root systems might have been damaged by standing waters during the flood period. These plants will generally recover, but they do not have the capacity for water absorption that they had before the flood; therefore, it is important that they be given adequate water during the summer and fall droughts when the temperatures are high and there is not enough rainfall to supply an inch of rain a week. This may mean watering the plants every four or five days. Give them a soaking to wet the soil a depth of 6 to 8 inches. If plants are watered and kept free of insect and disease pests, their chances of survival even after a flood are very high.
The same may not be said for plants growing in containers or pots. Such plants are not as well adapted to oxygen starvation caused by flood waters as are plants growing in soils. Container plants should be moved high enough so that flood waters do not reach their root systems. If this is done, no damage will occur to the container grown plants, provided they are given water during their stay out of the flood waters.