Photo courtesy usda.gov

Get rid of yellow starthistle

The weather is warming up, and that means weeds are sprouting. The weeds we should be most concerned about are noxious weeds — those that, by definition, cause economic loss and harm the native environment.

Noxious weeds choke out crops, destroy rangeland and pastures, clog waterways, affect human and animal health, decrease property values and threaten native-plant communities. The majority of Oregon's most noxious weeds are of European, Mediterranean and Asian origins.

One invasive weed we're quite familiar with around here is yellow starthistle (Centaurea solsticialis). A tap-rooted annual, it loves warm, south-facing slopes, but given the chance it'll occupy almost any unshaded piece of ground.

A starthistle plant can put out as many as 30,000 seeds per square meter, with about 95 percent of the seed being viable. Most seeds germinate within a year of dispersal, but some can remain viable in the soil for more than three years.

This is not a difficult weed to kill, but one must be persistent to get rid of it. If you've got starthistle on your property, you can bet there's seed in the soil that will germinate either later this year, next year or the year after that, so don't give up.

Annual weeds such as starthistle will succumb to a variety of treatments, including shovels, hoes, mowing, burning, herbicides, goats and insects. Five species of insects, or biological controls, have been released for more than 20 years in Oregon, so don't invest too much time or energy in that method. Instead, pull, dig, mow, chop, disk or burn. They're all viable ways to control this noxious weed. If possible, do it before yellow flowers appear. If you get to the plants after that, cut the flowers off and bag them for disposal later.

The best time to treat weeds is prior to seed production, which for starthistle is as early as late June. But that doesn't mean you have to wait until June — get busy as soon as you find it.

To learn more, see http://oregon.gov/ODA/PLANT/WEEDS. This website is one of the best sources of information about noxious weeds in Oregon.

If you have any questions, feel free to contact me.

Jacksonville resident Bob Budesa oversaw the noxious-weed program with Medford District Bureau of Land Management and helped start the Jackson Coordinated Weed Management Area. Reach him at 541-326-2549 or bob_budesa@yahoo.com.

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