Texas Forest Service offers guidance to determine which trees are 'definitely dead', 'likely to live', or 'questionable' after state's record-breaking drought
COLLEGE STATION, Texas
November 30, 2011
– Texas remains mired in one of the worst droughts in state history and it’s creating disastrous effects on trees and forests across the state.
After one of the driest years on record, many shade trees went into dormancy as early as August, dropping their leaves and branches in a desperate act of self-preservation. Pine trees with normally thick, green crowns ended up cloaked in red, dead needles while foliage on cedar trees turned completely brown.
The sight has created a dramatic effect on the Texas landscape and left many landowners wondering whether or not their tree is dead — or if it might recover and produce new leaves next spring.
Assessing trees damaged or killed by drought can be tricky, according to Dr. Ronald Billings, Texas Forest Service Forest Health Manager. He suggests grouping the trees into three different categories — definitely dead, likely to live and questionable — to help with the task.
It is easier to make this call for pines, Ashe junipers (cedars) and other needle-bearing, conifer trees. The determination can be more difficult for hardwoods, which are more commonly thought of as shade trees. In most cases, a red pine is a dead pine, Billings said, explaining that the same can be said for cedars with red needles. Once all or most of the foliage of a pine or cedar tree turns red or brown, the tree is incapable of recovering.
Pine trees in this stage probably are already infested with tree-killing bark beetles and will eventually harbor wood-boring insects, termites and other critters. Such trees should be cut down and removed, particularly if they are likely to fall on homes, buildings or power lines.
Shade trees — like water oaks, for example — that have lost all their foliage and are beginning to drop limbs or lose large patches of bark are most likely already dead and should be removed. Hypoxylon canker, a fungus that appears as gray or brown patches on the trunk of the tree, is another sign of a dead shade tree.
Likely to Live
This category includes shade trees with at least some green or yellow leaves still attached to the limbs. In fact, even those that have dropped all their leaves may still be alive. Some native shade trees, such as post oaks and live oaks, are more drought resistant than others like water oaks or elms.
You can use a scratch test to determine if the tree is dead or just dormant. If you scrape the bark off a small branch or limb and find green, moist tissue underneath, the tree is still hanging on, waiting for the next rain. That means you may need to wait until spring to see if the tree makes a recovery — unless the tree starts to drop large branches and patches of bark, which is a sign of death. If there is no green, moist tissue, the tree is likely dead.
An exception is the baldcypress, which also is known as a cypress tree. The tree is a conifer, but unlike pines and cedars, its foliage generally turns red and drops from the tree in the fall or during periods of drought stress. Cypress trees usually will re-sprout in the spring. If in doubt, apply the scratch test or wait until spring to be sure.
Pines with a few yellow or red needles scattered throughout an otherwise green canopy have a good chance at survival. Pine trees typically shed a large portion of their older needles every year as winter approaches, and then put on new needles in the spring.
Though it’s not as feasible to water your forest, any yard trees that show signs of life (green inner tissues or green foliage) should be watered deeply to reduce lingering drought stress.
Questionable trees are those that appear to fit somewhere between the Definitely Dead and Likely to Live categories.
A pine that is topped with brown or red needles but still has green foliage in its lower branches is alive, but likely will eventually die. That’s because bark beetles likely will invade the lower trunk at some point, killing the tree in stages.
When inspecting a questionable pine tree, look for popcorn-sized masses of resin (pitch tubes) or brown dust in the bark fissures. These are early signs of attacks by pine bark beetles. The foliage of the infested pine may still be green, but the tree is doomed. This is particularly true if you find bark beetle galleries or trails beneath the bark. Pines with these signs of bark beetle attack should be removed as soon as possible.
In the case of shade trees, those that have many dead or dying limbs or mostly bare branches may or may not survive. A few green, yellow or red leaves may remain for a while as the tree slowly dies, or it may recover when rains return.
It’s important to note that not all trees may be stressed from the drought alone. Some trees may also be suffering from insect infestations, disease or other forest health problems. If you’re unsure or have any questions, visit the Texas Forest Service web site or check with a certified arborist, forester or tree care professional.
Deciding whether to remove a questionable tree can be a tough decision for both property owners and professional tree care experts. Removal should be considered if a severely drought-stressed or fire-damaged tree is close to a house or other structure on which it might fall. If it is away from such areas, it may be more feasible to wait and see if the tree makes a comeback.
View examples of trees in each of the three categories on the Texas Forest Service facebook page: http://on.fb.me/rB5946.
Not sure what kind of tree you’ve got? Check out Texas Forest Service Tree ID: http://texastreeid.tamu.edu
Need more help?
Visit the Texas Forest Service web site: http://texasforestservice.tamu.edu
Download the Texas Forest Service Professional Management Services Referral List: http://tfsweb.tamu.edu/uploadedfiles/frd/referral.pdf
Go to the International Society of Arboriculture Texas Chapter Certified Arborist List: http://isatexas.com/Consumers/Find_a_Local_Arborist.htm