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 Diseases and Disorders Questions

Death of mature tulip tree in Raymond IL
June 06, 2010 - We have a mature tulip tree that leafed out and looked very healthy then all of the leaves turned brown and fell off. I think the tree is now dead. We live in the country and have a corn field behind ...
view the full question and answer

Plants to grow in high zinc, lead and copper soil in Los Angeles
January 24, 2011 - We live on the Westside of Los Angeles and have just been given the bad news that our beds are high in zinc (86.39), lead (45.98) and copper(12.95). Can you recommend some plants that may grow in thes...
view the full question and answer

Yellowing of St. Augustine grass in south Texas
June 04, 2009 - We live in deep south Texas, Roma, Texas to be precise and we have a problem with our San Augustine grass. In the spring its quite nice and green after a few weeks and one rain it is turning yellow.
view the full question and answer

Restoration of mistflowers suffering from wet season
June 27, 2007 - I have planted gregg's mistflower in a bed that receives morning sun and afternoon semi-shade. It was beautiful and covered with blooms and butterflies this spring, but suddenly has become brown and ...
view the full question and answer

Getting rid of algae on dirt and patio
January 12, 2011 - Algae and on patio and dirt, and how to get rid of same?
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
© 2014 Lady Bird Johnson Wildflower Center