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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 - May 04, 2014

From: Benson, AZ
Region: Southwest
Topic: Soils, Shrubs
Title: Chlorotic Texas Mountain Laurel in Benson, Arizona
Answered by: Jimmy Mills

QUESTION:

I've planted a Texas Mountain Laurel in heavy clay soil in Arizona. It's been in place for 3 years and flowers each spring. However it's leaves are a shade of medium, yellowish green nothing like the dark green of the mountain laurel trees around Tucson. I'm 40 miles east of Tucson at 4000' elevation. Is there something I need to do to improve it's condition? Thank you.

ANSWER:

This quote from the NPIN page for Texas Mountain  Laurel Sophora secundiflora (Texas mountain laurel) may give us a clue  about the problem you are facing: “Sophora secundiflora is very popular as a native evergreen ornamental tree within its range, valued for its handsome, dark green foliage and lush early spring blooms.”  This USDA distribution map shows us that  Arizona is not in its range.

Also from its NPIN  page, the Growing Conditions provides useful information.

Growing Conditions

Water Use: Low , Medium
Light Requirement: Sun , Part Shade
Soil Moisture: Dry , Moist
Soil pH: Alkaline (pH>7.2)
CaCO3 Tolerance: High
Drought Tolerance: High
Cold Tolerant: yes
Heat Tolerant: yes
Soil Description: Dry, rocky, well-drained, preferably calcareous soils. Sandy, Sandy Loam, Medium Loam, Clay Loam, Clay
Conditions Comments: Needs good drainage.

Your description of the problem that your Texas Mountain Laurel is having sounds like chlorosis, which can have several causes. Mostly likely in this case, the heavy clay is not providing good drainage which in turn is limiting the availability of iron to the plant. Iron is important in the pathway that allows the plant to produce chlorophyll. Low iron = low chlorophyll = yellow leaves.
I’m including links describing chlorosis, and tips for working with clay soils.

  iron chlorosis

  ammending clay soils

  improoving clay soils

For some help closer to home, you might want to contact the folks at the Cochise County office of the University of Arizona Extension Service .

 

From the Image Gallery


Texas mountain laurel
Sophora secundiflora

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