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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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Monday - November 15, 2010

From: Tucson, AZ
Region: Southwest
Topic: Compost and Mulch, Transplants, Trees
Title: Problems with Texas wild olive tree in Tucson
Answered by: Barbara Medford

QUESTION:

Planted a Texas Olive tree in Tucson, Az. Some of the leaves are kind of yellow. It gets part sun and part shade and is growing. Is this due to too much water, not enough water or does it need something like Miracle grow ?

ANSWER:

Cordia boissieri (Mexican olive), which also has the common name of Texas Wild Olive is endemic to Texas, which means it is not native to Arizona, and may be in conditions in which it cannot do well. When you follow the plant link above to our web page on this plant, you will notice this instruction in the Propagation Instructions:

"Maintenance: Requires much water to get it established but once established it is drought-tolerant."

From this USDA Plant Profile, you will see that Mexican Olive grows naturally no closer to Arizona than the extreme southern tip of Texas. You did not say how long ago this tree was planted, but transplant shock is quite common in recently planted trees, particularly if they have been planted in what is, for them, an alien environment. If it was planted pretty recently, then we would definitely recommend more water, allowed to drip in very slowly from a hose. The plant also needs good drainage; if its roots are in clay with no compost or other amendments to improve the drainage, the roots may drown in the water it is given.

Pima County, against the southern border with Mexico, is in USDA Hardiness Zones 8b to 9a, while the South Texas area where the Mexican Olive grows natively is Zones 9a to 9b, a little warmer, but probably not enough to make that much difference. It is more likely that lack of water when the tree was being established and possbly poor drainage and/or the wrong soil is causing the difficulty. And, if you planted it in the heat of an Arizona summer, or even fall, transplant shock is almost inevitable.

On the subject of fertilizing, don't. Any plant under stress, and yours obviously is, should not be fertilized. The fertilizer will try to push a plant to grow more profuse leaves, when what that plant is doing is struggling to survive.

From our Native Plant Image Gallery:


Cordia boissieri


Cordia boissieri


Cordia boissieri


Cordia boissieri

 

 

 

 

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