With the recent news that conifers in Indiana are struggling to survive the effects of drought, and may be at risk for the next five years or so, arborists, landscape professionals, municipalities and homeowners are on the alert for signs of stress. Further south, nearly all of Texas is in a state of drought, with conditions in the vast majority of acreage deemed by the U.S. Drought Monitor to be “severe” to “exceptional.” That’s as bad as it gets. It’s been predicted that Houston stands to lose millions of trees unless the area receives significant precipitation, but the current drought is already the third worst in the state’s history.


The “scorched” edge of this leaf is a sure sign of drought.
ROBERT L. ANDERSON, USDA FOREST SERVICE, WWW.BUGWOOD.ORG

Even if you work in a part of the country that’s not currently, “officially” affected by drought, chances are good that your region is recovering – or next in line. Take, for example, the Rockies. Snowpack throughout the mountain range this year was unusually high, thrilling resort owners and leading to threats of flooding and water-management challenges downstream. It’s a situation that might give some a false sense of security. But one season does not a reservoir fill, and the historic record shows a dramatic decrease in snowpack – read, available water – over time.

Competition for water is a fact of life. And when trees are forced to compete for moisture, the effects may not be immediately apparent. Significant signs of stress can take a few years to emerge, and once a tree becomes drought-stressed, it may be increasingly susceptible to pathogens.


Wilting foliage signals that this dogwood is suffering from drought.
BRIAN KUNKEL, UNIVERSITY OF DELAWARE, WWW.BUGWOOD.ORG

It’s not often easy to determine the cause of a distressed tree’s woes, and some of the visible symptoms of drought pressure mimic diseases and infestations. Nevertheless, be on the lookout for the following signs that your trees – and those on your clients’ properties – are struggling for a drink.

  • Wilt. One of the most immediate signs of drought stress is leaf wilt. Some species, such as Prunus, Cornus, Tilia and Betula may show wilt readily. Drooping leaves may indicate temporary wilting, which can be resolved overnight; permanently wilting trees must receive additional water in order to survive. Prolonged permanent wilt can kill the tree.
  • Leaf deformation. In deciduous trees, leaves may curl, bend or show signs of mottling and scorch. Trees may even shed leaves.
  • Color. Chlorosis may be evident, and unusually early coloring in autumn may occur. Conifers may experience yellowing or browning of needle tips.
  • Dieback. If drought intensifies, tree crowns may show signs of dieback.

Often mistaken for damage caused by pine beetles, the dramatic effects of drought are seen in the early abscission of longleaf pine needles.
ANDREW J. BOONE, S.C. FORESTRY COMMISSION, WWW.BUGWOOD.ORG

Less visible symptoms, such as growth inhibition that can affect shoots, roots and the cambium, are no less critical. So when you can spot external woes, it’s safe to assume that something’s going on deep inside the tree as well.

What if your season has been relatively “normal” in terms of moisture? Don’t forget that drought stress may take years to develop. Check weather and climate records – and, as always, check with an arborist.