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Weed watch: The Tumbleweeds of Fall |
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Written by Susan Donaldson
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Monday, 01 September 2008 |
September is my favorite month. Temperatures cool off just enough to make the outdoors delightful, and I can pick and eat tomatoes off the vine. However, it won’t be long before we start dodging weed skeletons as they roll across our yards and streets.
Tumbleweeds are iconic symbols of the West. Movies use images of tumbleweeds blowing in the wind to evoke visions of vast, empty spaces. There’s only one problem with the image: the weed that most people think of as a tumbleweed is called Russian thistle, Salsola tragus. It is a native of Russia, and was introduced into South Dakota around 1874 in a shipment of contaminated seed. While it spread quickly, it was not widespread in the West until the 1900s. Therefore, when it appears in movies set in the 1800s, a great deal of artistic liberty has been taken!
If you’ve ever cleared a portion of your property of all vegetation and left it barren, you’re familiar with Russian thistle. It’s the stickery, prickery, ball-shaped bushy plant that’s starting to dry out now (photo 1). An annual, Russian thistle starts sprouting in late spring and summer. The seedlings resemble tiny pine trees (photo 2). If you pull them out, you’ve killed the plant. Sounds easy, doesn’t it? The problem is that few people associate the cute little innocuous seedling with the mature, unpleasant plant, and they fail to take action until seeds have been formed. When the mature plants break off and tumble, they spread seeds along the way.
Russian thistle is not a very competitive plant, and the key to control is to establish healthy, competitive vegetation. It takes advantage of disturbed sites on which all competing vegetation has been removed, which is why it becomes such a problem on vacant building pads and cleared lots. It’s rarely a problem in well-maintained, vigorous landscapes.
If you’re unfortunate enough to have areas of disturbed soils on your property, don’t give up. At this point, chances are good that the plants have already made seed, so your job is to control next year’s sprouts. Depending on the scope of the problem, you have several choices. Study the photo and learn to identify the young plants (photos 2 and 3) . Then, pull the seedlings as they emerge. This method works well if you have a small infestation but may not be practical for larger patches. Consider applying a pre-emergent herbicide in the spring when the forsythia bloom. These chemicals kill emerging seedlings by stopping the growth of root hairs. Be sure to carefully read and follow all directions.
Postemergence herbicides containing glyphosate, such as Roundup, can be used on small, young plants. However, they are not effective on larger tumbleweeds, and won’t do anything if applied now. If you’ve waited too long, pull the plants and dispose of them. Or, wait until they dry out, collect them, and put them out with the trash. Next year you’ll know to expect sprouts in that area of your property, and you can watch for and remove the seedlings before they get out of hand.
Russian thistle is not the only weed that breaks off and tumbles, but it does seem to be the most common one locally. If you need help identifying weeds on your property, bring us a fresh sample of the plant, including leaves, flowers, stems and roots, if possible, and we’ll identify it for free. We’ll also provide recommendations for control.
For more information on weeds and water quality issues, contact Susan Donaldson, University of Nevada Cooperative Extension, 775-784-4848 or
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Susan Donaldson is a water quality and weed specialist for the western area of University of Nevada Cooperative Extension.
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