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 - December 13, 2009

From: Austin, TX
Region: Southwest
Topic: Diseases and Disorders, Trees
Title: Freeze damage to Mexican olive in Austin
Answered by: Barbara Medford

QUESTION:

I have a Mexican Olive tree/bush. It is young - about 8 ft. tall. This last freeze in Austin made many of its leaves turn black. I got this from your database: "Its native range extends no farther north than the Rio Grande Valley because it can't survive harsh winters, but it has long been grown in San Antonio and even in Austin, where cold winters can cause it to die back to the ground. Those surviving longest in San Antonio and Austin are protected from north winds." My question is what should I do now - just wait and see or do some pruning. It is one big "trunk" with many branches full of leaves. Thanks!

ANSWER:

We have been receiving many questions regarding what to do after the sudden hard freeze that occurred recently in Central Texas; in fact, we are still dipping below freezing at night frequently. One thing that applies in every case is, don't fertilize. Plants should be fertilized in the Spring, when you want to encourage new shoots to appear. The last thing you want to do is encourage new shoots now that will put more stress on already-stressed roots and probably just get frozen back again.

You may already know what happened; actively growing plants still have water in their upper structure, particularly the leaves. A sudden hard freeze causes that water to expand, bursting cell walls in the leaves, and they quickly turn dark and look pathetic. What made this freeze worse was that it was earlier than we ordinarily expect these conditions in this part of Texas, very sudden, temperatures went down very far, and remained below freezing for several hours. A gradual decrease in temperature over a period of time increases the ability of plants or plant parts to withstand cold temperatures. A sudden decrease in temperature in late fall or early winter usually results in more damage than the same low temperature in January or February.

The information that you found in our database is exactly what we know about the hardiness of the Cordia boissieri (anacahuita).  Was your plant protected from those hard, cold winds we had during our cold snap? If so, that might give you a better prognosis. The first thing to do is determine how much of the tree is still alive. Obviously, the leaves, probably black, are going to drop off. On the trunk and branches, use the thumbnail test. Scrape away a very fine, very small layer of the bark, beginning with upper branches and working down toward the base. If there is still some green beneath that scraping, that part of the plant is still alive. If it is black or even slimy beneath the outer bark, that portion of the plant should probably be marked for pruning. The good news is that the bark and woody portions of the tree have stronger cell walls, and are not so apt to burst in freezing. 

In your case, you are asking about pruning some damaged areas. From Texas A&M AgriLIFE Extension this article Follow Proper Pruning Techniques will give you some good information on what and when to prune. If you elect to prune now, in the interest of appearance, wait a few days first, as more damage may become evident as time passes. In any case, we would not disturb it except to remove dead areas, and wait to see if it starts to come back in the Spring. Hopefully, the roots were well enough protected by the soil to keep them from freezing, too.

This is an illustration of why the Lady Bird Johnson Wildflower Center recommends the use of plants native not only to North America but to the area in which the plant is being grown. You knew you were gambling to plant the Mexican olive this far north; we hope that you will ultimately win the gamble and retain a live tree. 

From our Native Plant Image Gallery:


Cordia boissieri

Cordia boissieri

Cordia boissieri

 

 

 

More Diseases and Disorders Questions

Rose canker in roses on cedar posts
May 24, 2007 - While visiting the wildflower Center I saw that some of the plants were growing on trellis' made of posts cut from cedar trees. I made a trellis for my climbing rose bush and where the stems touched...
view the full question and answer

Keeping cows from eating the garden
September 02, 2008 - I have a flowerbed area outside of our new split-rail fence available for planting, but cattle roam outside the fence also! Do you have any suggestions for plants that cows tend not to eat (unle...
view the full question and answer

Long term effects of pesticide from Lubbock TX
March 20, 2013 - I have 9 western pecan trees about 20 years old. Trunk sizes is from 18" to 39". I used a product Bayer Tree and Shrub, applied to the trees. I wonder what it will do to the trees. I talkd to Bayer ...
view the full question and answer

Watering Houseplants with Soapy Water
August 22, 2011 - I accidentally watered my house plants with a container that had a some dishsoap in it. Will they be okay? One of the plants is a 20yr old cactus, with small roots.
view the full question and answer

Problems with red tip photinia in San Antonio
March 29, 2009 - I have a red tip photinia that's about 20 years old and about 20 feet high--it is big! I noticed last summer the highest leaves looked droopy all the time even with deep watering and now that portion...
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