Recent torrential rains over the past 5 months and exceeding over 55 inches, have brought about flooded conditions and super saturated soils in many communities throughout our State. Some communities have reported rain fall as much as 67 - 72 inches from the beginning of the year. The heavy rains during the early growing season typically is more harmful to trees than during dormant periods. The longer exposure, the greater the potential for injury.

As flood and excessive ground waters recede and as the soils dries out, we begin to see the potential damage to our landscape trees and plants. Wet soil will have long-lasting effects of soil compaction, and oxygen depletion. It is difficult to say what the long-term effect of super saturated soils will be. When soils are completely flooded or saturated, oxygen is prevented from reaching the root system. Certainly, some trees are more tolerant of waterlogged conditions, but the longer the lack of aeration, the greater the chance of root death. The general thought is that most landscape plants can survive being submerged for about a week or so. However, extended lack of aeration to the roots will result in root die-back, with the above-ground symptoms appearing as leaf chlorosis and subsequent defoliation, droopy foliage, and eventually, crown and branch die-back. Waterlogged root systems are also more susceptible to attack by root-rot organisms. In areas of severe flooding, concerns for plant health also include soil erosion and deposits of additional soil and silt. Both can damage the root system. 

In addition to the obvious damage to trees, there are more long-term effects to soils, which have been flooded or waterlogged 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. Tree roots also must contend with high concentrations of toxic compounds like alcohol and hydrogen sulfide that accumulate in waterlogged soils. Under conditions of stress trees will normally drop leaves and go into a semi-dormant mode to slow down growth in order to protect itself from eventual death.

Water stressed trees are prime candidates for attack by "secondary organism." Several opportunistic disease-causing fungi and insects invade trees that are weakened or stressed. Water or drought stress impairs tree defense mechanisms and trigger biochemical responses that release carbohydrates, glucose and other nutrients which seem to stimulate secondary insects and diseases.  (Wood Borers) and fungal pathogen attack. (Canker Fungi)

There isn't much you can do other than wait for drier weather to prevail and allow water to drain. As more favorable conditions return, watch for signs of die-back, but don't be too hasty to cut limbs. Branches that have lost leaves aren't necessarily dead; even though leaves may drop, there may be buds that will be able to re-leaf yet this summer. Live stems and buds will have some green tissue visible. Remove only those limbs that are physically damaged or obviously dead. A light fertilization (low nitrogen) may be helpful to replace nutrients that were lost and to encourage re-growth. We may not know the full effect of flooding or excessive rains until long after the water recedes and soil return to normal moisture levels. And then, of course, a lot will depend on what future stresses the weather may bring upon our trees and landscapes. Very little is known about the effects of long term excessive rains during the growing season on many ornamental tree species. In fact, the full impact may not be known until a year after at the earliest.  It is important to remember that the symptoms may progress and ultimately result in tree death or they may subside indicating the tree has recovered.

" The Chemjet" http://www.chemjet.com.au/

Drought Stress:   http://www.oakwilt.com/articles/heatwave.html