Published on 01/08/09

Recent rains may provide too much water for trees

By April Sorrow
University of Georgia

Recent rains left soils soggy across the state. The muddy puddles are doing more than making a mess. The stress the pools of water are placing on trees can cause serious problems down the road.

The first week of 2009 brought five or more inches of rainfall to some North Georgia cities. Rome received 6.15 inches of rain between Jan. 1 and 7, according to the University of Georgia's Georgia Automated Environmental Monitoring Network. GAEMN recorded 5.47 inches in Blue Ridge, 5.12 inches in Calhoun, 5.10 in Gainesville and 5.12 in Lafayette.

“It seems strange to talk about too much water when we have experienced a drought for several years,” said Jean Woodward, a plant pathologist with UGA Cooperative Extension. “However, the drought-weakened trees, particularly those damaged by construction injury, are more susceptible to wood decay fungal diseases. Excess water now can increase disease development.”

Trees with stressed or damaged root systems are at a greater risk for disease and fallout, risking property damage and injury. Driving cars over root systems or cutting them for construction purposes damages the tree, too.

“The biggest thing homeowners can do is not stress them out,” Woodward said. “Avoid driving over saturated soils. Soils will become compacted and put the tree under greater stress. Once roots are damaged, the tree will slowly decline over time.”

A large amount of rainfall after trees have shed their leaves helps to limit the immediate risk of tree fallout. But, damage to root systems now will increase risks for falling trees when leaves and powerful thunderstorms return in the spring and fall.

“Trees being without leaves now is actually helpful,” Woodward said. “The biggest concern is with full canopy trees. When leaves become saturated with water it can weigh down the tree. The leaves also act like a sail capturing the wind making it more prone to fall in stormy weather.”

One thing to watch out for is fungal growth around the base of the tree.

“People will start seeing mushrooms around the base of the trees or conks coming off the trunks that indicate rot in the center of the tree,” she said. “Once you see these signs of disease, there is no control. The tree will continue to decline and you need to think about taking the tree down.”

But, these disease indicators won’t surface until the spring or fall and most often go unnoticed.

“Mushrooms and conks indicate that there is rot, but they don’t mean that the tree will die overnight,” she said. “Depending on the stress of the tree and the amount of damage to roots or trunks, the tree can die within a few years or live for more than 10 years.”

Woodward said the best thing to do to protect your trees is don’t injure plant roots and to correct conditions that may weaken the tree, such as diverting pooling water.

“During heavy rain, it is a good time to take a look and see if landscapes are draining well,” she said. “Check plants to see if water is pooling around them. If it is, try to redirect the water.”

She suggests adding extenders to downspouts and installing French drains to divert excess rainwater. Don’t add mulch to absorb the moisture. Doing so will only add more stress to the drowning plant as it will take away much-needed oxygen.

“There is not a whole lot people can do now except keep water from pooling,” she said. “It is that type of change that can help save those trees in the future.”

(April Sorrow is a news editor with the University of Georgia College of Agricultural and Environmental Sciences.)

April R. Sorrow is a science writer with the University of Georgia Public Affairs Office.

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