You’ve been granted free access to this subscribers only article.
Brown, shedding leaves are not always indication of dead tree
COLLEGE STATION -- “Our trees are dying!” Reports like this are coming from throughout the state, but don’t write off that shade tree or loblolly pine just yet, said a Texas AgriLife Extension Service expert in a Sept. 27 Texas AgriLife press release.
“It’s really a wait-and-see kind of a game,” said Dr. Eric Taylor, AgriLife Extension forestry specialist from Overton. “Just because a tree’s leaves have turned brown -- or that the leaves have shed from the tree -- doesn’t mean the tree is dead.”
Trees respond to moisture, stress, and heat with natural defense mechanisms, and these responses vary from species to species, Taylor said.
Southern red oaks, for example, will senesce -- draw back the nutrients from their leaves -- early in response to stress.
“It’s the pulling back of nutrients that causes the leaves to turn brown,” Taylor said. “That leaf has actually been abscised from the tree and is no longer functioning, but it doesn’t mean the tree is dead.”
Other species don’t have that defense mechanism. They will simply drop their leaves while they are still green, Taylor said.
“You see a lot of that with the trees with thicker, waxier leaves,” he said.
Some trees can’t just drop leaves. All they can do is wilt, according to Taylor.
“Now those leaves will be wilted past the point of recovery, but none of that means the tree is dead,” he said. “We’ll have to see what happens next spring. If the tree was happy and healthy and somewhat vigorous, then it will likely have enough carbohydrates and energy reserves to come back next spring.”
There are some trees that are more drought-tolerant, particularly species that have smaller leaves with a waxy covering, such as live oak.
Pines are different from hardwood trees in how they respond to drought and heat, he said. They don’t have the built-in senescent defense mechanisms of pulling back lots of nutrients from leaves.
“They have two years of needle growth, and they’ll tend to shed the oldest needles and hold onto the current needles, which is why many pines have both brown and green needles,” he said. “If those current needles begin to shed, then that’s a good indication perhaps that the tree is beyond the point of recovery.”
Taylor said newer needles are found on the tips of the branches, while the older needles will be farther inward.
Limb drop is another matter, he said. It has to do with the “water status” within the tree. When trees transpire out more water than they receive, the lignin or glue that binds cells together breaks down.
“The sudden collapse of spaces between cells will cause limbs to drop, even though they may still appear to be alive and functioning.”
Taylor said that trees in over-crowded stands are at higher risk of dying.
“You’ve got to look back at the last decade, because trees are very slow to respond. So it’s the last decade of extremely intense temperatures and drought that the trees today have to work their way through.”
Your Opinions and Comments
Be the first to comment on this story!
You must be logged in to post a comment.
Agriculture Today Archives
Bull Classic Dec. 5 (November 25, 2015)
Davidson: Reduce antibiotic use, dispel beef myths (November 25, 2015)
EPA proposes changes to pesticide applicator rules (November 25, 2015)
Farm Bureau responds to beef cancer claims (November 25, 2015)
Hay & Forage Report (November 25, 2015)
Livestock disaster funding available (November 25, 2015)
Livestock Market Reports (November 25, 2015)
Llama competitors shine in state, national shows (November 25, 2015)
Plan to attend grazing lands conference (November 25, 2015)
Plant cool weather veggies (November 25, 2015)
Rancher’s Choice bull sale Dec. 5 (November 25, 2015)
Skills team places sixth (November 25, 2015)
TPWD announces annual trout stocking (November 25, 2015)
All Breed Bull Sale Nov. 21 in Nixon (November 18, 2015)
Clean Water Rule continues to make waves in Congress (November 18, 2015)
Conservation Service: Tips for planting winter pastures (November 18, 2015)
County committee elections begin (November 18, 2015)
Hay & Forage Report (November 18, 2015)
Here’s the beef: Patterson wins FFA national title (November 18, 2015)
Livestock Market Reports (November 18, 2015)
Moczygemba: Angus group CEO (November 18, 2015)
Onion recommendations (November 18, 2015)
A river runs through it: River changes spark border dispute (November 11, 2015)
Cold-sensitive oriental hibiscus (November 11, 2015)
Gov. Abbott: EPA’s Clean Power Plan is ‘power grab’ (November 11, 2015)
Hay & Forage Report (November 11, 2015)
Knowles winner of mule deer hunt package (November 11, 2015)
Letter: A war on Texas: Bureau of Land Management vs. Texas ranchers (November 11, 2015)
Livestock Market Reports (November 11, 2015)
Palo Alto College hosts FFA leadership conference (November 11, 2015)
Rodeo athletes place in Hallettsville contest (November 11, 2015)
‘Old Iron’ club show canceled! (November 11, 2015)
Antique Farm Equipment Demonstration and Field Day, Nov. 14 (November 4, 2015)
Cattlemen’s seminar Nov. 14 in Kosciusko (November 4, 2015)
Hay & Forage Report (November 4, 2015)
Impacts of rural land loss (November 4, 2015)
Livestock Market Reports (November 4, 2015)
Rain can be blessing, curse for farmers (November 4, 2015)
Ranch Rodeo fun in Nixon (November 4, 2015)
Ranching event set for Nov. 11 in Panna Maria (November 4, 2015)
Tips for spraying broccoli, cabbage (November 4, 2015)
Wet winter, spring is good news for hunters (November 4, 2015)
November 2015 Gardening Calendar (November 1, 2015)