Native Plants
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.
Did you know you can access the Native Plant Information Network with your web-enabled smartphone?
Ask Mr. Smarty Plants is a free service provided by the staff and volunteers at the Lady Bird Johnson Wildflower Center.
rate this answer
Saturday - August 30, 2008
From: Boerne, TX
Region: Southwest
Topic: Compost and Mulch, Diseases and Disorders, Soils, Trees
Title: Yellow, pale green leaves on Cedar Elms in Texas
Answered by: Barbara Medford
QUESTION:
I have had several cedar elms of various sizes planted in our yard over the last 10 years. Only the largest has dark green, healthy looking leaves. All the others have yellowish, pale green leaves. The poor color look is more pronounced this year than before. Do you believe this is a soil problem?ANSWER:
The diagnosis is that the leaves on the smaller elms are chlorotic, or not having enough chlorophyll in the leaves. Chlorosis is caused by the failure of the tree roots to absorb enough iron from the soil for the creation of chlorophyll, with which the plant manufactures food. Ulmus crassifolia (cedar elm) prefers moist to dry, alkaline soil. In Boerne, in the Texas Hill Country, you have the alkaline soil, but not necessarily the moist soil. But even for a plant preferring a slightly alkaline soil, the Central Texas soils can be too alkaline to permit the plant to take up iron in the soil. In excessively wet or poorly drained soils, the chemistry of the soil changes and iron becomes unavailable.
Here are some things to try to prevent chlorosis. Improve the soil-work compost in around the roots, this will also help make the soil drainage better. Apply iron sulfate, blending with organic matter like compost and concentrate the mix in soil near plant roots. Apply iron chelate-these organic compounds keep iron soluble and available to roots. Scatter the dry granules within plant's drip line, then water thoroughly. Leaves should start to green up in 2 to 3 weeks.
The website Ulmus crassifolia (USDA Forest Service) mentions that Elm leaf beetles and aphids can infest the Cedar Elm. The elm leaf beetle can seriously defoliate a tree, but is not a cause of yellowing, and defoliation is usually not too severe. Aphids also may suck fluids out of the leaves, causing them to yellow; again, not a big threat. Aphids can usually be identified by the honeydew they deposit on the undersides of leaves, which often hosts sooty mold, turning the leaves dark gray or black. Another disease that has yellowing leaves as a symptom is Dutch Elm Disease (USDA Forest Service. This disease is usually fatal, and there are other more compelling symptoms on the tree besides yellowing leaves.
In answer to your question, is this a soil problem, yes, we believe the alkalinity of the soil and/or poor drainage is probably the reason the leaves are turning yellow. If only the smaller trees are showing these symptoms, it is probably because their roots are not getting good enough drainage to permit them to draw on the minerals in the soil. See the first paragraph for compost around the roots and drainage improvement.
More Trees Questions
How to tell the girls from the boys in wax myrtles (Morella cerifera)
May 14, 2010 - How would I be able to identify whether my wax myrtles are male or female plants? I was given two plants last fall (that came from a family members back yard) and the person who gave them to me didn'...
view the full question and answer
What are the grey-green plants on oak trees in San Marcos, TX?
March 12, 2011 - The oak trees in the neighborhood in San Marcos, TX, are covered with clumps, or balls, of gray/green fluffy-looking plants. they remind me of bromeliads. You can pull and knock them off; after wind ...
view the full question and answer
Non-native avocado trees in Rio Grande Valley from Austin
January 05, 2013 - I just read the article in the Austin American Statesman about growing avocados outdoors. Don't know if they grow here, but they certainly don't just grow in south Florida. I used to live in Wesla...
view the full question and answer
Tag on oak tree in Buda, TX
April 02, 2008 - I found a large oak tree on my property with a tag that has a number on it. Any idea what that means?
view the full question and answer
Privacy screen from Simpsonville SC
May 04, 2013 - My neighbor cut down his part of our shared woods so now we see his whole "outside patio area". What kinds of fast growing shade loving trees and shrubs can we plant on our property line that will c...
view the full question and answer
Support the Wildflower Center by Donating Online or Becoming a Member today. |