Host an Event Volunteer Join Tickets

Suppport the plant database you love!

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
4 ratings

Saturday - September 20, 2008

From: San Antonio, TX
Region: Southwest
Topic: Diseases and Disorders, Pruning, Watering, Trees
Title: Leaves dropping on native Texas Mountain Laurel in San Antonio
Answered by: Barbara Medford

QUESTION:

Please help. We have a beautiful TX Mountain Laurel in our front yard. This year the leaves are dropping like snow in the north. What do you think is wrong with our tree?

ANSWER:

Last year this time, when people were worried about their Sophora secundiflora (Texas mountain-laurel) trees, we were advising them that it was the result of too much rain, and the drainage in the soil the mountain laurel was planted in was probably poor. This year, we're thinking it may be because it has been so hot and dry all summer. Sometimes you can't win. However, we will try to find a possible cause for the leaves dropping, but we don't have all the facts we need. Has your tree been very recently transplanted? The Texas mountain laurel does not transplant well, it has a long taproot and, if that is damaged, the survival of the tree is adversely affected. Or, if you have been trying to overwater it to help the problem, and the soil is not draining well, the mountain laurel roots might be drowning, just as certainly as if it had rained too much. 

Other possibilities include over-fertilizing. The Sophora secundiflora is a legume, and has a mechanism by which it can fix nitrogen in the soil, for its own use and for other plants to borrow. This is a plant accustomed to growing in rocky, alkaline soil, and pretty well taking care of its own needs. For the time being, don't fertilize at all, no plant under stress should be fertilized. The mountain laurel, unfortunately, is not very resistant to disease, and one to which it might be prone is cotton root rot. This is a disease of warm earth and hot weather, and only occurs in the Southwestern United States. It is a soil-borne fungus, and will quickly take out any vulnerable plant growing in that soil. See this Texas A&M University website on Controlling cotton root rot on ornamental plants.That site will also give you instructions for trying to diagnose if that is the case. Should it prove to be cotton root rot, do not plant any other plants susceptible to the disease in the same soil.

If you don't feel that any of these possibilities is the cause, we suggest you treat the tree as though it is under stress, and treat like transplant shock. First, check the drainage of your soil. If you stick the hose down in the soil around the roots of your mountain laurel, let it drip slowly until the water appears on the surface, and then the water stays for a half hour or so, your drainage is poor. Without disturbing the roots any more than you have to, try to incorporate some organic material like compost or leaf mold into the soil to improve the drainage. Water deeply but infrequently. Trim off 1/4 to 1/3 of the upper structure of the tree, including the dying leaves. Leave as many green leaves as possible to improve the nutrition of the tree. 

And, then, it's just watch and wait. This is an incredibly tough tree, growing in the wild almost out of solid rock, and certainly without a sprinkler system. It may take it a while to recover, but hopefully by next Spring your beautiful tree will be coming back. 

 

More Trees Questions

Lopidea on Texas Mountain Laurel from Austin
April 16, 2012 - How do I get rid of the Lopidea ALL OVER my Texas Laurels and boring into the seed pods?
view the full question and answer

Plant Suggestions for a Partly Sunny Steep Bank in Illinois
November 09, 2013 - I am looking to plant something on a steep clay bank on our Illinois property. It is on the edge of our dirt road with trees above the bank and is partly sunny. What would work best for that type of a...
view the full question and answer

Does Chilopsis linearis, var.Bubba produce seed pods? No.
October 01, 2007 - We have a really beautiful 2-year old Bubba, Desert Willow. It is already about 12 feet tall. I really have two questions. One does the Bubba form the seed pods like the other types of Desert Willows?...
view the full question and answer

Is Texas Mountain Laurel Honey Toxic in Fulshear, TX?
March 11, 2012 - Toxicity of Texas Mountain Laurel HONEY I know the seeds and leaves of the Tx Mountain Laurel are toxic. But, is honey that comes from the Mountain Laurel toxic too? I heard that it is, but can'...
view the full question and answer

Southern Magnolia Damaged by Deer
April 16, 2015 - I have a young Southern Magnolia (about 6 feet tall) that was damaged by deer on the main trunk. The bottom 2 feet looks okay, but where they damaged it and tore branches off, and above that, the leav...
view the full question and answer

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