Rush Skeletonweed, an Idaho Noxious Weed

A weed is considered “noxious” when it is harmful to the environment or animals. According to Idaho's Noxious Weeds booklet, Rush skeletonweed (Chondrilla juncea) is one of the 69 plants designated as a noxious weed by Idaho’s Department of Agriculture. Equipped with knowledge, together we can help curb the spread of this harmful plant in Idaho.

What is Rush skeletonweed?
Rush skeletonweed is an invasive, non-native, long-lived biennial or perennial that is very persistent, taking years for established colonies to be eradicated.  It is not toxic, being palatable for most livestock, especially sheep and goats (only goats will eat the wiry stems). These stems are so tough that they can interfere with harvesting equipment, making them a bane for farmers raising grain crops. In the West, it is estimated that over 6 million acres are infested with Rush skeletonweed, and those numbers are likely to continue to grow.

Rush skeletonweed germinates or re-sprouts in the fall and early spring as a rosette (looking very similar to young dandelions), actively growing through the spring and early summer.  All the while it is establishing a formidable root system that can be 7’ deep with many side shoots, which can form future rosettes. In early summer, as the stem develops the leaves of the rosettes begin to die back. If it is allowed to progress to this point, it cannot be killed chemically.

The small bright yellow flowers produce ripe seeds, without fertilization, in a few days.  These seeds can then be dispersed by the wind miles away. An established, vigorous plant can produce an average of 20,000 seeds each year.

Rush skeletonweed prefers well-drained, rocky, or sandy-textured soils in climates that are cold in winter, warm in summer, and wet early in the year. Areas that have been disturbed, such as roadsides, empty urban lots, burn scars, logging sites, cultivated fields, droughty areas, and areas that have been overgrazed, seem to be favorable sites. South and central Idaho is currently the epicenter of the infestation, with wheat-growing regions and rangelands being particularly hard hit

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How can we mitigate this noxious weed?
First, it helps to know that eradicating Rush skeletonweed is a long-term project (possibly seven years or longer), so be patient.

Spraying rosettes with herbicides both in fall and winter is preferable, and spring treatment is also effective. Unfortunately, 2,4-D, and a round-up type product won’t do the job.

Hand pulling is effective if done when seedlings are less than 5 weeks old.  Once the roots have developed, mark the spot, and return periodically to re-dig because  2 or more roots will likely re-grow in the same spot. This method is preferred in your vegetable garden or other areas where you cannot use chemicals.

As mentioned above, grazing is effective, but must be continuous or you will end up with more rosettes or more flowering stems. Controlling and eradicating Rush skeletonweed is a very serious issue. If you have it on your property, take proactive measures to ensure it does not flourish and spread.