Contact Us Host an Event Volunteer Join

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

Please forgive us, but Mr. Smarty Plants has been overwhelmed by a flood of mail and must take a break for awhile to catch up. We hope to be accepting new questions again soon. Thank you!

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

Drought-resistant plants for Paradise, California
January 23, 2009 - We are moving to a new home in Paradise, CA. What drought resistant plants do well in Paradise ? Thank you !!
view the full question and answer

Trimming of cordgrass plants
November 20, 2007 - We have planted more than 150 cordgrass plants (spartina bakeri) along the edges of the small pond at our condominium complex to try to prevent any further soil erosion between the buildings and the p...
view the full question and answer

Ornamental grasses for North Carolina coastal region
March 09, 2016 - What ornamental grasses will grow in pure sand and withstand salt-laden winds in zones 8 a and 8 b?
view the full question and answer

North Dakota Riverbank Stabilization
July 17, 2012 - Can you suggest plants to prevent and stabilize river bank erosion on Sheyenne River, ND? Must be tolerant to cold, varying level of salts and sulfates and water level (from drought to flooding)
view the full question and answer

Best Time for Dividing and Transplanting Native Bunch Grasses in Jarrell, Texas
February 02, 2011 - Dear Mr. Smarty Plants, What time of the year is the best for dividing and transplanting native bunch grasses like Gulf muhly, and Miscanthus?
view the full question and answer

Support the Wildflower Center by Donating Online or Becoming a Member today.