Weed Seed: Chondrilla juncea (Rush skeletonweed)

Family

Asteraceae

Common Name

Rush skeletonweed

Regulation

Primary Noxious, Class 2 in the Canadian Weed Seeds Order, 2016 under the Seeds Act.

Distribution

Canadian: Occurs in BC and ON (Brouillet et al. 2016Footnote 1).

Worldwide: Native to northern Africa, temperate Asia and Europe. Introduced to North America, Argentina, Latvia, Australia and New Zealand (USDA-ARS 2016Footnote 2). Infests millions of acres in Washington, Idaho, Oregon and California (FNA 1993+Footnote 3).

Duration of life cycle

Perennial

Seed or fruit type

Achene

Identification features

Size

  • Achene length (without style): 3.0 - 4.0 mm
  • Achene width: 0.5 - 1.0 mm
  • Length of achene style: 5.0 - 6.0 mm

Shape

  • Achene is oblong, tapering to a truncate base, compressed laterally

Surface Texture

  • Woody, dull, with small overlapping flat spines at the top of the achene

Colour

  • Achene is yellow-brown

Other Features

  • A remnant style extends from the top of the achene which is usually broken off in samples.

Habitat and Crop Association

Cultivated fields, pastures, rangelands, forests, roadsides and disturbed areas (Darbyshire 2003Footnote 4). A serious weed of wheat in Australia (FNA 1993+Footnote 3).

General Information

Rush skeletonweed was first reported in the United States near Spokane, Washington in 1938 (Shelly 1994Footnote 5), and is now found in the northern regions and California (Kartesz 2011Footnote 6). Rush skeletonweed is often found on well-drained, light soils (Shaw et al. 2008Footnote 7).

One plant may produce as many as 15,000–20,000 seeds (Ministry of Agriculture, Food, and Fisheries 2002Footnote 8). Seeds are dispersed by wind and animals over considerable distances (Shaw et al. 2008Footnote 7).

Similar species

Dandelion (Taraxacum officinale)

  • Dandelion has a similar oblong shape, yellow colour and style remnant as rush skeletonweed.
  • Dandelion achenes are shorter, wider, a darker colour and the flat spines at the top extend further down the achene than rush skeletonweed.

Photos

Figure 1 - Rush skeletonweed (Chondrilla juncea) achene
Rush skeletonweed (Chondrilla juncea) achene
Figure 2 - Rush skeletonweed (Chondrilla juncea) achenes
Rush skeletonweed (Chondrilla juncea) achenes

Similar species

Figure 3 - Similar species: Dandelion (Taraxacum officinale) achenes
Similar species: Dandelion (Taraxacum officinale) achenes
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