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Sunday - June 06, 2010

From: Austin, TX
Region: Southwest
Topic: Trees
Title: Cottonwood seed clogging air conditioner in Austin
Answered by: Barbara Medford


My husband and I recently moved into a rental house that has a very tall cottonwood tree in the backyard. It has been shedding its seeds all over our yard since the beginning of May and seems to still be going full speed. It looks like snow, but snow that clogs up our A/C unit. I would like to know how much longer it will probably be seeding (we are in south Austin, 78744) and if you have any suggestions for our landlord as to how we can save our A/C unit from being constantly clogged.


Populus deltoides (eastern cottonwood) is native to Travis County and its seeds have long been the bane of anyone living around it. In particular, those flying puffs of cotton are extremely allergenic. The cottonwood itself is not very popular, as it tends to drop big limbs, has large roots, and weak wood. It grows very fast, particularly in a moist area, and you can still see them coming up in creek beds in Texas. We found a website from Hortiscope Questions on Cottonwood that has all kinds of good information, including the name of a product thought to inhibit the cotton production. We were never able to find any information on how much longer the cottonwoods will be flying cotton in the Austin area, but the above-mentioned website said that it usually lasts about 4 weeks. Depending on where the tree is growing, of course, that will be earlier or later in the Spring than now. 

In terms of a filter for the air conditioner, that is out of our line of expertise. We recommend you or your landlord contact an air conditioning contractor. If there are many cottonwoods around, you can bet this is not the first time this question has been asked, and the contractor should have some sort of solution.

By the way, after many questions on how to stop the cotton flying, the author of the article we referenced, Ron Smith, Horticulturist for the North Dakota State University Extension Service, said the only way he knew of was to cut the tree down.

From our Native Plant Image Gallery:

Populus deltoides

Populus deltoides

Populus deltoides

Populus deltoides




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