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Monday - August 18, 2008

From: Kaufman, TX
Region: Southwest
Topic: Trees
Title: Avoiding cedar elm because of allergens
Answered by: Barbara Medford

QUESTION:

Hi. Cedar elm, Ulmus crassifolia, seems like a wonderful, tough, drought tolerant native tree. I'd like to plant several to shade buildings. I'm being discouraged from doing so because Cedar elm pollen is allergenic. I've been researching and having a hard time finding out how far the pollen travels and how bad it really is. There's plenty of Cedar elm growing on nearby properties, so isn't the pollen going to be blowing around anyway, whether we plant more of the tree or not? Or does it make a significant difference for allergic people if they walk under a tree? Thanks.

ANSWER:

In Texas, the calendar of allergies from tree pollens appear March through May. These are mostly pollens of ash, oak, box elder, hackberry, sycamore, walnut, elm, hickory, pecan, mesquite, and mulberry. The Fall Elm, or Cedar Elm, pollinates in August, September and October. Grass pollen season extends from May until August. Weed pollens are predominant July through October. For most parts of the country, winter is pollen free, but in Central Texas we have "cedar" (Ashe Juniper) December through March. Conclusion: If you live in Texas and have sensitivity to allergens (which lots of people do) you are going to have problems with pollen virtually year-round. This information came from an excellent website from BNet Business Network "Trees 'n Sneeze".

It has been suggested to you, apparently, that you not plant a particular tree (Cedar elm) because of its pollens. Pollen is the result of plants needing to reproduce themselves. The pollen is a vital link in that need, and there is going to be pollen, regardless. The benefit you are seeking is shade for buildings, but this Trees Are Good website "Benefits of Trees" gives many more benefits. As you pointed out, there are lots of other Cedar elms around, and you would not be contributing a great percentage to the allergy problem. All of the trees listed on the calendar of allergies are native, which is good. We are going to list the trees we consider as good shade trees for your part of the state, and you can follow the links to our web pages which will give you more information on each tree. Considering that all are going to put pollens in the air, you can then choose a tree that is best suited for your purposes.

Fraxinus americana (white ash)

Quercus palustris (pin oak) - good in East Texas, likes sandy, acid soil

Acer negundo (boxelder) - fast growing, planted for shade, but short-lived

Celtis occidentalis (common hackberry)

Platanus occidentalis (American sycamore)

Juglans nigra (black walnut)

Ulmus crassifolia (cedar elm) - susceptible to Dutch Elm Disease

Carya texana (black hickory)

Carya illinoinensis (pecan) - slow growing, difficult to transplant because of large taproot, susceptible to a number of pests and diseases.

 

 

 

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