Skeletonweed (Chondrilla juncea) is classified as a noxious weed in many areas, though it is not a plant native to the United States. Difficult to eradicate, this perennial spreads well and can be locally abundant.
There are relatively few leaves on each plant, and they tend to be narrow and deeply toothed. The color of the leaves and flower stems is dark green.
This weed usually blooms from early summer to early fall, depending on the area and the growing conditions. The flowers are yellow, with numerous blooms on each flower stalk. The plant is low growing, but the flower stalks can attain a height of up to four feet. The flowers give way to a large number of small seeds, up to 20,000 on a healthy plant, which can then be easily spread. Even a gentle breeze can carry the seeds quite some distance.
The main mechanism for the spread of skeletonweed is through seeds, especially when they are cut down or mowed. The roots can also cause spreading. Like dandelions, which they resemble superficially, the tap root of this plant tends to grow deeply, while side roots branch out in all directions. This causes difficulty in controlling the weed, because if a small root is left when digging it up, the root will soon grow into another plant. Since the roots can grow several feet deep, it is difficult to dig them up.
According to the Oregon Department of Agriculture, plant division, though first noticed in the mid 70’s in Oregon, skeleton weed is abundant now in 7 counties, and can be found in several more. The areas it is most populous tend to be hot and damp, with well drained soil. However the plant can grow in areas that are more arid as well.
Washington state also classifies this plant as a noxious weed, and it can be found in roughly half of the state. Even the US Department of Agriculture classifies Chondrilla juncea as a noxious weed. The plant now grows in a large number of states, particularly in the east and west, while the middle of the US appears to have so far escaped this problem plant. The weed can now also be found growing well into Canada.
Skeleton weed is tolerant to many herbicides. There are biological controls available, including a fungus, a midge, and a mite. However, these appear to simply lower the number of seeds produced, rather than actually controlling the spread of the weed. The plant, especially young plants, also resemble dandelions in many ways, enough to make identification more difficult. Identifying the plant becomes much easier once it blooms. Dandelions only have one compound flowering head per flower stem, while skeletonweed has many.
At this time, there are no controls that are reliable in controlling the spread of this noxious weed, though efforts are continuing to find something that will be more effective.
Oregon State Extension Service