Drought is a very real threat to plants in Washington, even on the ‘wet’ side of the mountains. Here are some classic symptoms to be on the lookout for, in order from slight to more severe:

  • Severely drought stressed street trees. Photo by Linden Lampman, DNR

    Leaves are pale, dusky or yellowish in color. Water is a key ingredient in photosynthesis. If water is limiting then photosynthesis bogs down and leaves become less vibrant, almost like a light bulb going dim if the flow of electricity is reduced.

  • Leaves are limp, wilty or curled. Each leaf contains thousands of plant cells. Think of each cell like a tiny balloon. If the cells are full of water then leaves are ‘inflated’ and they stick out horizontally. If water is reduced, the cells ‘deflate’ and leaves begin to droop or curl.
  • Early fall color. If drought stress persists into late summer, affected trees have less energy to photosynthesize and make more energy for themselves (ever heard the expression, “it takes money to make money”?). Some trees may go dormant early, turning fall colors in August or September. This is the tree cutting its losses in hopes of a more ‘profitable’ growing season next year.
  • The tree canopy is thin, and leaves are small. This symptom indicates chronic stress from previous years of drought. Chronically drought stressed trees have less energy to make new leaves, which may result in fewer and smaller leaves produced by the tree in spring.
  • Twigs are stiff or brittle. Woody stems are also made up of thousands of plant cells. When woody cells are flush with water, it acts like a lubricant, allowing twigs to bend and flex. When woody cells dry out they become stiff. If twigs snap easily in your hand then you tree is under severe drought stress.
  • Leaves are shriveled, brown or appear scorched. This is a symptom of extreme drought stress. When wilted leaves are purged of all their water, the leaf overheats in the sun and cells are literally cooked to death by the summer heat. If you have brown leaves then you probably have brittle twigs as well. Affected parts of the tree may be dead.
  • Cracking bark. This is another severe drought symptom. If the living cells behind the bark dry out and die, the bark will crack, split and separate from the trunk. If your tree’s trunk is this dry, then the prognosis is not good.

Keeping your trees well-watered will help them stay hydrated and healthy. Here are a few related Tree Link articles you might find interesting:

Drought Damage Dynamics

Tree Watering is No Joke, or is it?