Extended Dry Spell Prompting Leaf, Nut Drop

First posted on 08-03-2010

A prolonged period of dry weather and triple-digit temperatures has stressed some trees so much they’re dropping leaves and fruit, said Tamara Walkingstick, associate director-Arkansas Forestry Resources Center for the University of Arkansas Division of Agriculture.

“As water becomes less available, trees become more stressed,” she said Monday. “Essentially, they begin to shut down, beginning with the leaves and photosynthesis.

Even if this week’s forecast rain happens, it may be too late in some cases. The National Weather Service at Little Rock was predicting only a 20 to 30 percent chance of rain through Saturday.

“This week’s predicted rainfall might help some, but the trees already losing their leaves might not re-leaf this growing season,” Walkingstick said. “It takes a lot of energy for a tree to put on leaves and even more to set fruit or nuts.”

She said she expected oaks and hickories to begin shedding their acorns and nuts as the trees try to conserve what water and energy they have stored.

While watering may be helpful to the grass, most homeowners can’t even scratch the surface for their trees’ water needs by running the sprinkler.

“At maturity, an oak can use 250 gallons of water in one day,” she said. By comparison, a shower without a low-flow head will use five gallons a minute. Watering that single oak would take as much water as a 50-minute shower.

Still, some water is better than none. Walkingstick also advises mulching around the tree to help conserve what soil moisture is left.

Fertilizing is also a bad idea because it prompts the tree to seek more water and increases transpiration, making a bad situation worse.

The effects of a prolonged drought can have longer-term effects.

“Drought-stressed trees are more vulnerable to attack by insect pests, especially pines,” Walkingstick said. “Hardwoods are also affected because growth for the next season is being established during the current summer - so stressed trees may have fewer buds next spring.”

Other dry weather effects include the drying and contraction of roots and the ability of the tree to resist wind, becoming more dry and brittle.

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