RELEASE DATE: March 6, 2015
Live Oaks in Springtime
by Amanda Steves
Sometime during March or April, you may find yourself wondering, “What’s happening to the live oaks?” This is the time when they change the way they look almost weekly. And then things start dropping—more than just leaves—like yellow dust, crunchy brown tassels, and of course, worms.
In late winter or spring as temperatures warm up a little, the first thing that happens is the leaves can start looking bad. They may turn brown, yellow, or splotchy. This is how the old leaves die to make way for new ones. Over a couple of months, more will turn brown and new leaf buds begin to show up. As the old leaves start to fall, the new leaves will pop out, revealing a fresh, light green color. The best thing you can do for your live oaks is to resist raking and bagging the fallen leaves. You can mow over them to create mulch that will, over time, give the leaves’ nutrients back to the trees.
Live oaks are sometimes considered to be evergreen, but really they are semi-evergreen. This is because they actually do drop their old leaves every year, but the process is fairly quick compared to regular deciduous trees. Live oaks generally drop leaves as the new ones are coming out, so the trees never look completely bare.
Sometimes if your tree is especially old, stressed, or diseased, all of the leaves can fall and weeks or months will go by before the new ones bud out. This is not unusual--the tree can go on to lead a healthy, normal life in years to come. You might consider giving these trees some tender, loving care during the year, such as water every two weeks in dry spells, a layer of compost spread on the ground underneath, or some vertical mulching. This is done by drilling 15-inch deep holes in the ground and filling with peat moss and slow-release fertilizer. It’s a great way to help stressed trees recover.
At the same time as the leaves are changing over, something else is springing forth from the boughs: catkins. These greenish-yellow tassels contain the tree’s pollen and start out as little brown buds at the ends of twigs and bases of leaves. They will burst into 2-3 inch-long strands studded with nodules. They are the male flowers, and when they release their pollen it ends up in the air and on windshields and just about everything else in the vicinity. When the male catkins dry up and fall to the ground, it creates a crunchy, dusty mulch for the tree. Less obvious, the female flowers are so small that you are likely to need a magnifier to see them close to the leaf axils.
Another “dropping” that comes from live oaks this time of year is the brigade of tiny worms descending from the trees on invisible threads of spun “silk.” They are leaf-roller caterpillars, and in great enough numbers these little guys can defoliate a tree before they take the plunge. The other caterpillar pest that appears in live oaks is the “wooly” worm. It’s the larva of the white-marked tussock moth, and you can recognize it by its white bristles. But don’t touch one, because it causes an itchy rash for most people. Both types of caterpillar are part of the oak’s natural living environment, and they don’t usually cause catastrophic damage unless the tree is already in very poor health. Live oaks have a great backup system in the form of secondary leaf buds that will come out in cases of defoliation this time of year. If you feel that you must eradicate caterpillars, try spraying with Bt (Bacillus thuringiensis) while they are still eating leaves.
If you are tempted to prune your live oak in the spring, don’t do it. Oak wilt is a deadly disease spread by sap beetles from infected trees to healthy trees. At this point in time, oak wilt has not arrived in the coastal bend counties (although it is as close as Goliad County), but it’s very easy for a sap beetle carrying the oak wilt spores to hitch a ride in a bundle of oak firewood and arrive at your doorstep. The beetle can infect a tree by drinking sap from a fresh cut or wound. So play it safe, and avoid cutting your live oaks. If you must, wait until cold weather--January or February--and paint each cut immediately with pruning or latex paint.
Texas A&M AgriLife Extension Service - Aransas County Office is located at 892 Airport Road in Rockport. AgriLife Extension education programs serve people of all ages, regardless of socioeconomic level, race, color, sex, religion, handicap or national origin.
References
“Don’t Panic…Live Oak Leaf Drop Is Normal” by Ginger Easton Smith, Aransas County Extension Agent, March 2012, http://aspmastergardeners.org/files/2010/06/April-2012-Live-Oak-Leaf-Drop-by-Virginia-Easton-Smith.doc
“Live Oaks Shed Their Leaves – Fertilizing Trees,” by Elayne Arne, Master Gardener, Aransas/San Patricio Master Gardeners, February 26, 2007, http://aspmastergardeners.org/files/2010/06/2007-02-26F-ARN-Live-Oak-Leaf-Shed.doc
“White-Marked Tussock Moths – ‘Willy Worms’,” by Todd L. Cutting, Master Gardener, March 29, 2012, http://aspmastergardeners.org/files/2010/06/April-2012-White-Marked-Tussock-Moths-by-Todd-Cutting.doc
“Spring Invaders – Tussock Moths and Oak Leaf Rollers,” by Charlotte Wall, Master Gardener, Aransas/San Patricio Master Gardeners, March 5, 2007, http://aspmastergardeners.org/files/2010/06/2007-03-05F-WALLTussock-Moth-and-Oak-Leaf-Roller.doc
“Things You Should Know About Live Oak Decline,” from Plant Answers, Aggie Horticulture, http://aggie-horticulture.tamu.edu/plantanswers/trees/oakwilt.html
“March Garden Checklist,” by Aransas/San Patricio Master Gardeners, Feb. 2015, http://aspmastergardeners.org/files/2014/12/March-2015-March-Garden-Checklist-compiled-by-Amanda-Steves.doc