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Montana Field Guide

Montana Field Guides

Rush Skeleton-plant - Lygodesmia juncea

Native Species

Global Rank: G5
State Rank: S5

Agency Status
USFWS:
USFS:
BLM:
MNPS Threat Rank:
C-value: 4

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General Description
Rhizomatous perennial. Stems erect, branched, 15–50 cm. Herbage glabrous. Leaves cauline, alternate, linear, 5–30 mm long; the upper reduced to scales. Heads ligulate, solitary on branch tips; involucre obconic, 9–16 mm high; phyllaries in 2 series; outer minute; inner ca. 5, linear, glabrous, scarious-margined; receptacle flat, naked. Ray flowers perfect, ca. 5; ligules 9–12 mm long, pinkish. Pappus off-white, capillary bristles. Achenes fusiform, 6–10 mm long, 5-ribbed, glabrous (Lesica 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Diagnostic Characteristics
Rush Skeleton-plant (Lygodesmia juncea), Rush Skeletonweed (Chondrilla juncea), and Thorny Skeletonweed (Pleiacanthus spinosus) can be confused by their common name, scientific name, and/or first appearance! All are members of the Aster or Sunflower Family, Asteraceae, and exhibit green stems that are leafless or inconspicuous leafy (few, small, and linear). All have flowerheads made of only ray florets (ligulate). Yet Rush Skeletonweed is exotic and designated Noxious, Rush Skelton-plant is native and designated desirable, and Thorny Skeletonweed is native and designated desirable and a Species of Concern in Montana. How do you differentiate them?

Rush Skeleton-plant:
* Pinkish flowerheads occur at the tips of stems. About 5 florets per flowerhead.
* Achenes are not beaked, but sometimes are fusiform.
* Plants lack milky sap.
* Plants are without hairs (glabrous).
* Plants are rhizomatous perennial forbs.

Rush skeletonweed:
* Yellow flowerheads occur at the tips of stems or in the axils of leaves. About 7-15 florets per flowerhead.
* Achenes (fruits) have a beak of 5-6mm long.
* Stems, leaves, and inflorescence have milky sap.
* Plants have hairs being hirsute to glabrate. On the lower 10-15 cm (4-6 inches) of the stem the hairs point downward while the upper stem is lacks hairs or has a few rigid hairs.
* Plants are taprooted perennial forbs.

Thorny Skeletonweed:
* Pinkish flowerheads occur solitary on upper branches. About 3 florets per flowerhead.
* Achenes are not beaked, but are tubular.
* Plants have a milky sap.
* Plants have hairs, being glabrate to weakly tomentose.
* Plants are taprooted with a brown-woolly branched crown.
* Stems are spine-tipped and branched.

Species Range
Present
 


Range Comments
BC to MB south to AZ, NM, TX, IN and MI (Lesica 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Observations in Montana Natural Heritage Program Database
Number of Observations: 48

(Click on the following maps and charts to see full sized version) Map Help and Descriptions
Relative Density

Recency

 

(Observations spanning multiple months or years are excluded from time charts)



Habitat
Grasslands, sagebrush steppe, open forest, roadsides; plains, valleys (Lesica 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

References
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Citation for data on this website:
Rush Skeleton-plant — Lygodesmia juncea.  Montana Field Guide.  .  Retrieved on , from