En EspaŅol

Q. Who is Mr. Smarty Plants?

A: There are those who suspect Wildflower Center volunteers are the culpable and capable culprits. Yet, others think staff members play some, albeit small, role. You can torture us with your plant questions, but we will never reveal the Green Guru's secret identity.

Help us grow by giving to the Plant Database Fund or by becoming a member

Did you know you can access the Native Plant Information Network with your web-enabled smartphone?

Share

Ask Mr. Smarty Plants

Ask Mr. Smarty Plants is a free service provided by the staff and volunteers at the Lady Bird Johnson Wildflower Center.

Search Smarty Plants
    
 
See a list of all Smarty Plants questions
Can't find the answer in our existing FAQs, submit a question to Mr. Smarty Plants.
Need help with plant identification, visit the plant identification page.
 
rate this answer
1 rating

Sunday - May 27, 2012

From: Denton, TX
Region: Southwest
Topic: Non-Natives, Diseases and Disorders, Planting, Grasses or Grass-like, Trees, Vines
Title: Oak trees shedding leaves in Denton TX
Answered by: Barbara Medford

QUESTION:

In Denton, TX we have two mature Quercus buckleyi. It is May 11th 2012 and one of these trees has been shedding green leaves for the last week. The only changes we have made are: planted English ivy plants, grass seed and jasmine in three different areas of bare ground under the oak tree. No major roots were disturbed and the ground has been watered daily, though not heavily, to establish the new plantings. The leaves do not resemble those typical of oak wilt, not can I see any symptoms of fungus. The leaves left on the tree are still green, although some have a bronze tinge. There appear to be small scale insects on the undersides, at the vein nodes. Any idea why my tree is covering the ground with apparently healthy leaves?

ANSWER:

In spite of your feeling that you did no damage underplanting your Quercus buckleyi (Texas red oak), it does seem more than coincidental that the tree began to show signs of distress following the underplantings. This USDA Plant Profile Map shows that while this oak does not grow natively in Denton County, it does in nearby Tarrant, Dallas and Cooke Counties. Follow the plant link above to learn about its favored soils, etc. In particular, we think this extract is important:

"Soil Description: Medium Loam, Clay Loam, Clay, Limestone-based
Conditions Comments: Q. buckleyi is more drought tolerant than the Shumard oak, but less hardy. This tree tolerates alkaline soil as well as neutral and slightly acidic soil."

We have had questions on oaks in your area of Texas recently that we think had to be related to the soil type. Texas has so many soil types and different soils can be just blocks apart sometimes. However, it looks like this oak can tolerate different soils, so we won't blame the problems on that.

On the subject of the insects on the underside of the leaves, this USDA Forest Service Oak Leaf Aphids article has a picture of those aphids, which you can compare with those you are seeing. This should not be a deal breaker for the oak; note that they can be controlled with natural enemies. That is to say, don't spray insecticides because that would kill the ladybugs who are the natural enemy of aphids.

From the Abilene TX Online Reporter News, here is an article by Bruce Keitler that we think hits the nail on the head, Red Oak Leaf Drop Can be Unpredictable. Note that your oak is a red oak.

One final word, when you put all those things under your tree, did you fertilize them? That can be another problem. We don't recommend fertilizing native plants (which your trees are and the other plants are not) because they are already acclimated to the local soils. If you fertilize a plant, and of course your oak roots took up anything you put on those new plants, you are urging it to put on new leaves. This is stress on the plant and in your case, the stress was already caused by the underplantings. It will start dropping leaves to relieve the load.

There is good news and bad news. The good news is that the oak trees will probably survive. The bad news is that the plantings underneath will probably not. Oaks are capable of allelopathy, which is emitting substances that discourage competition beneath them, and will likely cause too much shade for the grass. The ivy and jasmine can take the shade but will try to  spread away from the oak and could become invasive in other parts of your garden. We don't make the rules, Nature does.

 

From the Image Gallery


Texas red oak
Quercus buckleyi

Texas red oak
Quercus buckleyi

Texas red oak
Quercus buckleyi

More Grasses or Grass-like Questions

Problem with Habiturf. Is it dormant or dead?
July 24, 2013 - We planted habiturf in spring 2012. It's beautiful. But since last summer, we have had one area that seems to go dormant much more rapidly than the rest, even though it receives the same amount of ...
view the full question and answer

Failure to thrive of Cherokee sedge in Spicewood, TX
May 18, 2009 - I have several Cherokee sedges, just planted in March. Three of them are doing fine, but the rest look like they're dying. Some are right next to one that is doing great. Any ideas?
view the full question and answer

Non-native, and/or invasive bermudagrass, St. Augustine and Pistache from Houston
September 24, 2012 - Our St. Augustine lawn died suddenly this summer from either chinch bugs or grub worms (or both?), and a multitude of weeds and native Bermuda have taken over the area. Now that the weather has cooled...
view the full question and answer

Native grasses for wildlife in Katrina recovery area of Louisiana
June 21, 2009 - I live in La in an area decimated by Katrina and want to establish 11 acres of wildlife friendly native short grasses. It is partly designated wetlands because it floods, but also has long periods wi...
view the full question and answer

Native plants for cemetery north of Dallas
May 16, 2009 - I need something to plant on a grave in a country cemetery north of Dallas. There's no water piped to the site; it's basically just a pasture. I'm hoping to find a native plant that will be fairly ...
view the full question and answer

Smarty Plants's Facebook profile Support the Wildflower Center by Donating Online or Becoming a Member today.

Mr. Smarty Plants wants you to be his Facebook friend. Click the Facebook icon to add yourself to Mr. Smarty Plants list of friends.
E-NEWSLETTER | BECOME A MEMBER | DONATE NOW | MEDIA | SITEMAP | STAFF
© 2015 Lady Bird Johnson Wildflower Center