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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.

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

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Sunday - October 06, 2013

From: Edinburg, TX
Region: Southwest
Topic: Watering, Trees
Title: Problems with Mexican Olive tree from Edinburg TX
Answered by: Barbara Medford

QUESTION:

My Mexican olive (anacahuita) shows no obvious signs of pest or disease, but over the last years has more and more dead limbs and smaller and smaller leaves. It's in a yard with a sprinkler system that is regularly watered. I've tried less water, I've tried more water, I've tried fertilizer stakes, and it continues to go downhill. When we get a good rain, though, it's VERY happy, with bigger leaves and blooms. Do you have any suggestions on how to duplicate that effect the 300+ days it isn't raining? (I live in the Rio Grande Valley.) Thank you!

ANSWER:

If you follow this plant link, Cordia boissieri (Mexican olive), to our webpage on this plant, you will find this line: "Native Distribution: Rio Grande valley of Texas south to San Luis Potosi in Mexico." So at least you know you are growing it in the right area. Now, let's look at the Growing Conditions of this plant, and try to figure out the problem:

"Growing Conditions

Water Use: Low , Medium
Light Requirement: Sun , Part Shade
Soil Moisture: Dry , Moist
Soil pH: Alkaline (pH>7.2) , Circumneutral (pH 6.8-7.2)
CaCO3 Tolerance: High
Drought Tolerance: High
Heat Tolerant: yes
Soil Description: Well-drained caliche, sand, sandy loam, medium loam, clay loam, clay, or gravel soils
Conditions Comments: Prefers well-drained soil and full sun. Requires mild winters. Regular watering necessary to establish it, but once established within its natural  range, it can be left on its own, making it a popular highway planting in the Valley."

What makes Mr. Smarty Plants ears perk up is always the phrase "well-drained soil." We are not crazy about watering trees with sprinkler systems. Sprinklers well out in the shade line of the tree will be good for those roots spreading out there, but directly on the trunk of the tree can contribute to mold or fungus problems and does not get the water to the area where it is needed most - the main roots right under the trunk. Also, you probably should have your soil tested. Our growing conditions say this tree does well in clay loam, but not necessarily in clay itself. If your soil is all clay, water may be standing on the roots and causing problems.

From the Yucca Do Nursery, here is an article on the Mexican Olive, which contains this line: "Excessive irrigation and fertilization can result in exuberant, brittle growth that is susceptible to wind damage."

So, we have several questions you can ask yourself in the course of trying to figure out your problem, since we don't do house calls.

1. How old is your plant? We could find no projected average mature age for it, but if it is beginning to decline from age, there is little that can be done about that.

2. Is it possible you are over-loving your desert tree? The quotation above would have us believe that too much water and fertilizer (or any) is not good for it.

3. Do you have a soil that will allow proper drainage around the roots? Again, reduction of the amount of water and a soil test could help.

Hopefully, attention to some of these details will help you solve your problem. We suggest you contact the Texas A&M AgriLIFE Extension Office for Hidalgo County to see if they know what your soil situation is and if they know of other gardeners having similar problems. 

 

From the Image Gallery


Mexican olive
Cordia boissieri

Mexican olive
Cordia boissieri

Mexican olive
Cordia boissieri

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