Weed of the Month: Skeletonleaf Bursage

For this Weed of the Month, we’re laying bare skeletonleaf bursage—bones and all. Although it’s a native, it competes with crops and can cause severe allergic reactions. We’ve got the tips and tricks to managing and eliminating this pest. 

Skeletonleaf Bursage Origins:

Skeletonleaf bursage (Ambrosia tomentosa) is a North American native, but that doesn’t mean you should give it a warm welcome. Its dense stems and root systems can harm crops, and it’s highly aggravating to people with ragweed allergies—so an infestation is nothing to sneeze at.

Skeletonleaf Bursage: Plant Description

Skeletonleaf bursage is a small, herbaceous perennial in the Asteraceae (aster) family. It has silver-green to light brown stems that span from 4 to 24 inches. Its green-gray leaves grow alternatively on the stem and are hairy on top, smooth/hairy underneath, and can be pinnately or bipinnately lobed. 

Skeletonleaf bursage produces small, yellow flowers that are male or female. Males grow in spike-like inflorescences at the top of the plant, and female flowers grow in small clusters in the upper leaves

Skeletonleaf Bursage Habitat

Native to North America, skeletonleaf bursage grows in the central west, including the Great Plains, the Colorado Plateau, and the eastern Great Basin. It can be found alongside roads, in waste areas and in the sandy parts of plains, but can be a problem when it invades pastures, prairies, and cultivated fields.

Skeletonleaf Bursage Growth

Skeletonleaf bursage forms dense strands spread by seeds and an extensive rhizomatous root system. Skeletonleaf bursage flowers from early to late summer, and it spreads to new areas by green/brown seeds produced in small burs. 

Skeletonleaf Bursage Management

Although skeletonleaf bursage is native to our ecosystem, it’s still a problem for crops and agriculture and people with severe allergies. Because it’s native, no biological control agents exist. Luckily, management isn’t too hard.

Prevention and cultural control should be used first, like mowing before seeds take root or hand pulling and disposing of small seedlings before roots take hold. In case of an infestation, hand pulling and mowing is not recommended because root fragments can resprout.

Herbicides are effective in case of a larger infestation. Spring and fall treatments are ideal, but treatment on bolting plants can work too. Always read the label before using any herbicide, and contact us if you have any questions.

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This species is not actively managed through TCWP programs, but we’re happy to provide guidance and tips on how you can remove an infestation.