Desert Dandelion - Malacothrix torreyi
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Desert dandelion is limited in Montana to a few localized sites on the south side of the Pryor Mountains. Impacts of grazing are unknown, but it may respond positively to moderate levels of disturbance. Additional data on population levels and trends are needed.
Desert Dandelion is a taprooted annual with milky sap and a basal rosette of leaves giving rise to one to several erect or ascending stems that are 1-3 dm high. The basal leaves are up to 10 cm long, have petioles, and are deeply pinnately divided into toothed and pointed lobes. The few stem leaves are reduced upwardly. The foliage has sparse long hair when young but is glabrous with age, other than the sparse, glandular hairs in the inflorescence. The several stalked flower heads arise from reduced upper leaves, or bracts, in an open inflorescence. Flower heads nod in the bud but become erect in flower. Each is 8-13 mm high with 2 series of involucral bracts, the outer of which is very short, and the inner of which is long-pointed. Rays are yellow and ca. 1 cm long, and disk flowers are lacking. The cylindrical achenes are 5-ribbed, 3-4 mm long, and topped by a pappus of numerous unbranched, white bristles that are united at the base and fall as one when seeds mature.
Flowering takes place in June.
Several genera have yellow dandelion-like flower heads on leafy stems. Species of Hieracium differ in that they are perennial and have leaves with entire or shallowly lobed margins. The genus Lactuca has involucral bracts in more than two series and Sonchus has clasping stem leaves. Species of Crepis are perennial or have shallowly lobed leaves.
WY, eastcentral ID, and southcentral MT to southeast OR, south to AZ, NV, and possibly CA. Disjunct.
Observations in Montana Natural Heritage Program Database
Number of Observations:
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(Observations spanning multiple months or years are excluded from time charts)
Desert dandelion occurs locally below 1525 m (5000 feet) on the south side of the Pryor Mountains (Lesica and Achuff 1992). Information from the few known occurrences suggests that it prefers sandy alluvium, often occurring with Artemisia tridentata, Atriplex gardneri, Astragalus geyeri and Bouteloua gracilis.
This species is an annual, suggesting that population sizes may vary greatly between years. The low stature and annual habit also suggest that it may suffer from competition with larger plants, may require sparse vegetation and could respond positively to moderate levels of disturbance (Lesica and Achuff 1992).
Populations are subject to grazing, but the effects are unknown. Grazing removes the palatable, more competitive grasses and may favor species like M. torreyi. However, many species in the Tribe Lactuceae are palatable to ungulates.
- Additional ReferencesLegend: View Online Publication
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- Davis, W.S. 1986. Reproductive biology of Malacothrix (Asteraceae). American Journal of Botany. 73:758-759.
- Lesica, P. and P.L. Achuff. 1992. Distribution of vascular plant species of special concern and limited distribution in the Pryor Mountain desert, Carbon County, Montana. Unpublished report to the Bureau of Land Management. Montana Natural Heritage Program, Helena, MT. 105 pp.
- Lesica, P., M. T. Lavin, and P. F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p.
- Tomb, A. S., D. A. Larson, and J. J. Skvarla. Pollen Morphology and Detailed Structure of Family Compositae, Tribe Cichorieae. I. Subtribe Stephanomeriinae. American Journal of Botany. 61(5):486-498.