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When I first moved to the great American Southwest, I took a drive up to Mesquite to see some more of Clark County. It happened to be quite a windy day on the I-15.
The size of the tumbleweeds that were rolling along the highway, threatening my car’s undercarriage, was amazing. They were enormous. Of course, I’d seen westerns; tumbleweeds were a symbol of the old west, right?
Nope. Not exactly the old west, not even the western hemisphere. Actually, there’s more than one plant that turns into a tumbleweed, but the most common villain is Russian thistle. It was introduced into this country in the 1870’s, apparently in some Russian flax seed. Guess that’s why we don’t have a linen industry.
Its proper name is Salsola tragus, although it has a number of synonyms. In fact, some researchers think that several different species might have been lumped into that one. Don’t worry too much about the nomenclature; we all know Russian thistle. When it first appears, you might think that it’s some kind of grass shoot. When it’s in the little immature stage, it’s even edible – not that I’ve ever tried it, mind you. As it starts to mature though, you see it branching into a thick mass of slender red stems and green leaves. It produces thorns at the ends of its leaves, and they’re quite unpleasant to touch.
But it’s a green plant, like so many others. It has flowers, although you need to get up very close to see them. They’re tiny and prickly, but rather pretty, when you’ve braved all the thorns to look at them. After the flowers are pollinated, they produce seeds.
What’s so special about Russian thistle, and the other tumbleweeds as well? It’s the very effective seed dispersal system. Because Salsola’s an annual, it’ll only produce flowers and seeds once in its life, and then the plant dies. Underground, it doesn’t have an impressive root system. It’s got a long thin taproot, but not much side branching to hold it in place.
This dead parent plant, which can be as much as six feet across, is attached to the earth only by a slender shoot that dries up into a brittle stem.
It just takes a strong breeze to break off the whole dry plant, which by now is a spiny, leafless tumbleweed, covered by seeds. As it rolls along, it can drop seeds for miles. Some researchers in California reported that one plant can produce a million seeds.
You rarely see it in the untouched wild lands of the desert, but once the ground’s been broken, whether for construction, roads, or somebody being careless riding their ATV, then it will get established. A little water helps, but being such a tough plant, it doesn’t need much to gain a foothold. This is one reason it’s on California’s noxious weed list.
It’s called a “thistle” because of its prickly nature, although it isn’t related to any of the other thistles. Botanically, it’s a cousin of spinach and beets. One of its many problems is that it harbors the beet leafhopper insect. This insect carries a virus, which attacks those plants, as well as melons, tomatoes and other things. Obviously, this isn’t anything you’d want close to the vegetable garden you worked so hard to create.
Many weeds escape recognition because they’re really attractive. They were brought into a new environment because people figured they’d be a good addition to the plant palette. Russian thistle does not fall into this category. I don’t imagine anyone would be tempted to let it take over.
If it should appear in our own yards and gardens, most of us’ll pull as soon as we realize that it’s nothing we planted. It’s more of a problem along fences and in vacant lots. If possible, try talking to the property owner; see if they’d remove the plants before they go into flowering and seed production. Remember, one weed plant, a million weed seeds.
For KNPR’s Desert Bloom, this is Dr. Angela O’Callaghan of the University of Nevada Cooperative Extension.
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