Prescription For Flood And Salt-Damaged Plants
by Dr. Robert Black, Consumer Horticultural Specialist

It is very difficult to determine exactly how much damage will occur to plants and lawns which have been flooded and remained under water for long periods of time as well as being exposed to damaging salt conditions.

Severity of damage will depend upon the type of plant, age of plant, amount of salt, soils, period of submergence, and amount of debris, mud, etc. Only time will reveal the true amount of damage. Surprisingly enough many plants which appear in poor condition will survive, and prove to be of value in the landscape, thus they should not be destroyed, but cared for instead.

Normally tempermental plants such as roses, camellias and azaleas will suffer heavily, whereas rugged plants such as Indian Hawthorn, Ligustrum, Oleander, Pyracantha, and others may have a good chance of survival.

Once waters recede, immediate care should be given to valuable plants. Foliage and branch areas should be washed with a strong stream of water to remove all salt, mud and debris.

Excess amounts of soil or silt which has accumulated around or over root areas should be removed. Excessive soil over root areas may cause serious damage to the already weakened plant.

Survival of flooded plants will also depend on later environmental conditions. Intense sun may cause severe damage by scalding the previously flooded plants. In this case, prized plants may be temporarily shaded with an overhead structure covered with burlap, tar paper, plyboard or similar materials. Construct structure so as not to touch foliage, or hinder good air circulation.

Some plants such as junipers, pittosporum, pampas grass, black olive and live oak will tolerate salt conditions; whereas other plants quickly die under such conditions. Removing excessive salt from the soil is not an easy task. However, it can usually be removed or the amount reduced to an extent that plants will survive. This is accomplished by leaching (flushing soil with fresh water). On well drained soils leaching proved to be successful because water moves fairly easily through the soil. On level, moderately poorly drained soils leaching can be done by building a small dike (3 to 4 inches) around the plant or bed and filling (ponding) with fresh water. Allow water to stand for no more than two hours during the cooler part of the day. Repeat several times. After initial leaching or ponding, the soil should be kept moist but not so wet as to cause root damage from the lack of air. Water plants about every third day. For heavy, poorly drained soil situations with high salt concentrations, removal of the soil may be necessary to eliminate the salt.

Lawn grasses will of course encounter heavy damages from flooded conditions. Again, amount of damage, or likely survival will depend upon salt conditions, condition of grass at the time of flood, conditions after the flood, and type of lawngrass. St. Augustine grass will tolerate some salt and flooded conditions and is less likely to be damaged than other grasses.

All lawngrasses should be freed of fallen leaves, silt, mud and debris, which will smother the grass. Begin irrigating with fresh water as soon as waters recede and apply more water and more frequently than under normal conditions. Waiting for symptoms of salt damage to appear could result in serious damage to your lawn.