Starthistle

The most visible - and possibly the most obnoxious on the Rogue River National Forest is starthistle.

Photos courtesy of Weeds of the West 5th Edition.

StarthistleMany of you may not realize that this weed is a "newcomer" to much of the forest. Over the past twenty years, this weed has taken over more and more fields as well as moving into wildlands. Often, a few plants will appear along a road and in the next few years move in and take over a whole field. This plant out competes our native vegetation and some of our less obnoxious non-native plant species which are generally pretty aggressive. Alien plant species are becoming one of our biggest problems in maintaining our native plant communities.

What is it? Starthistle is that yellow spiny flowering plant along roadsides and invading fields. It is a winter-hardy annual that normally begins growth in the fall. The plant begins to bolt in late May and June and flowers from mid June to mid July depending on the weather and elevation. Plants can mature at any height from 3 inches up to 4 feet. Two types of seeds are produced by the flower, one with a white plume that carries the seed in the wind (up to about 30 feet from the plant) and one without a plume that drops below the plant. About 95% of the seeds produced are viable. Many seeds may remain alive but dormant in the soil for several years and will germinate and establish any time conditions are favorable. From 20-40% of the seeds may remain alive after one year and 10% can lie dormant for more than 10 years. Root development of yellow starthistle proceeds faster than that of native perennial grasses and is able to capture moisture, nutrients, and sunlight before other plants begin to grow.

Starthistle can cause "chewing disease" (a type of poisoning) in horses. This does not appear to be too much of a problem with horses in our area now but could become more of a problem by accumulating in the horse over time. If horses have other feed they usually leave the starthistle alone but sometimes a horse might develop a taste for it and eat more than normal. Signs do not become evident until the horse eats starthistle in amounts nearly equivalent to the animal's body weight and may not appear until several weeks after the horse has eaten the starthistle. These signs might first be noticed as abnormalities in walking or other movements. More severe cases are when the muscles of the lips, face, and tongue become stiff and swollen and the horse is unable to eat or drink.

Habitat requirements? Starthistle does well in dry areas with lots of sunlight. Shade and watering seem to reduce the number of plants. Irrigation probably affects the amount of starthistle by helping other plants grow well and out compete the thistle. Starthistle has a deep taproot and can utilize deeper water than many plants.

two photos of Starthistle: Immature leaf and mature bloomHow does it spread? Starthistle commonly starts along roads and appears to be spread by road maintenance work, heavy earth moving equipment, and by vehicles. These plants can hitch-hike in a number of ways that we might not think about. Starthistle plants get caught in car doors and then drop off when the car door is opened. Plants have been noticed on dozer tracks from a dozer that had been hauled out to the Applegate from the Rogue Valley. Starthistle can also be spread by wind, animals (sticking to their legs), hikers, motorcycles, bicycles, and any number of other methods.

Controls? Competition with other plants is very important in shading out the starthistle and competing with it for moisture and nutrients. If you can irrigate your pasture or yard you'll have a good chance in reducing the amount of starthistle plants and those that do remain could be pulled. A recent article in the Medford Mail Tribune featured trials by the JacksonCounty Extension Service with Berber orchard grass ascompetition with starthistle. Success has also been achieved locally by planting dryland alfalfa. Burning and plowing seem to make excellent habitat for starthistle and cause it to increase if done at most times of the year. Areas where the starthistle was cut at just the right time of year (when it's just starting to flower before seeds are forming) resulted in reduced numbers or total elimination. Some work has been done with herbicides but if you do try herbicides you need to target individual plants and plant something that will compete against the starthistle seed and will germinate the next year.

On the Applegate Ranger District, there exists several "small" scattered areas of starthistle (all but two along roads) as well as large populations around Applegate Lake and on the lower part of Beaver Creek Road. Eradication methods have included pulling individual plants in the small areas which in some cases has eliminated the starthistle while in other cases plants still remain (from seed left in the soil). In a couple of the larger sites a weevil was release but does not appear to have done much good. Another site was mowed after the plants began flowering and this site is now being evaluated. At this time, control tactics do not include herbicide use or planting of non-native species.

To reduce/eliminate populations of starthistle on the Rogue River National Forest we all need to work together. This is a big problem but if we start taking action we can do something about it. If you see a small population getting started - pull it up before the population gets too big and gets harder to control. If you've been successful in eradicating starthistle - let us know what you've done. Contact Barbara Mumblo or Jeanette Williams (541) 899-1812 and share what you've learned or to get more information. Randy White, with the Jackson County Extension Service (541) 776-7371, can fill you in more about the trials they have conducted to find plants that can out compete starthistle.