Pottery Milkvetch - Astragalus ceramicus var. filifolius
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Astragalus ceramicus variety filifolius is associated with sandy soils of the sandhills and sandstone outcrops in eastern Montana. It is known from about 20 occurrences observed mostly from 1983 to 2000. Some populations occur in State Parks. The Flora of the Great Plains (1986) considered it rare for the region except in the Nebraska sandhill area where it was somewhat common. Based on aging data, limited distribution, and an association to specific habitat types it is considered a Species of Concern. Current data on locations, populations sizes, and threats is greatly needed.
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Pottery Milkvetch (Astragalus ceramicus var. filifolius) Conservation Status Review
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PLANTS: Perennial from rhizome-like caudex-branches (Barneby 1964). The root-crown is deeply buried but can become exposed by shifting sand of mobile dunes (Barneby 1964). Plants are densely strigose (Lesica et al. 2012). Stems solitary, lax to ascending, 10–25 cm (Lesica et al. 2012).
LEAVES: 1–12 cm long. Mostly pinnate with 1-7 leaflets; the terminal leaflet is longest and confluent with the rachis (Lesica et al. 2012). Petioles are slender (Barneby 1964). Stipules are lanceolate, 2–6 mm long, and often united basally.
INFLORESCENCE: Racemes of 2-10(25) white to light purple flowers. Racemes with spreading to ascending flowers grow among the leaves (Lesica et al. 2012).
In Montana we have two varieties: filifolius and apus (refer to Diagnostic Characteristics and Range Comments).
Astragalus ceramicus is unique in being diffusely cryptophytic (bears its buds below the soil), with confluent terminal leaflets, and an inflated pod that does not lose its red mottling (Barneby 1964). Its pods (fruits) are balloon-shaped, large, and red-mottled.
Variety apus has pods that are sessile to the stem and is endemic to Beaverhead County and adjacent Idaho (Lesica et al. 2012). Pods are 2-4 cm long and about 1.5-2.4 cm in diameter (Barneby 1964). Lateral leaflets are wanting or nearly so (Barneby 1964).
Variety filifolius has pods that have a stipe of 1-3 mm length and grows in the counties of eastern Montana, adjacent North and South Dakota, and other regions of the Great Plains (McGregor 1986, Flora of the Great Plains). Pods are (2)3-5 cm long and 1.4-2.6 cm in diameter (Barneby 1964). Some lower leaves may have 1-2(3) pairs of lateral leaflets (Barneby 1964).
Variety apus is endemic to Beaverhead County and adjacent Idaho (Lesica et al. 2012).
Variety filifolius grows in the counties of eastern Montana, adjacent North and South Dakota, and other regions of the Great Plains (Barneby 1964). It is rare in the Great Plains except in the sandhill region of Nebraska where it is common (McGregor 1986, Flora of the Great Plains).
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)
Sand or very sandy soil of sandhills, below sandstone outcrops; plains, valleys, montane (Lesica et al. 2012).
Long distances between occurrences is thought to reduce opportunities for pollen exchange and has led to the perpetuation of small regional differences that consist of many minor races (Barneby 1964). Three varieties have been recognized since at least 1964: ceramicus, apus, and filifolius of which the latter two occur in Montana and are depicted in their own Plant Field Guide accounts.
Flowers white to light purple; calyx white- and/or black-strigose; sepals 2–3 mm long; banner reflexed, 8–11 mm long; keel 6–8 mm long. Legume ovoid, inflated, 15–40 mm long, maroon-mottled, glabrous, papery, pendent (Lesica et al. 2012).
The removal of natural disturbance regimes, including fire, ungulate grazing and pocket gopher activity, leads to dune stabilization and reduces the extent of early seral blowout vegetation areas upon which this species depends. Painted milkvetch would benefit from restoration of the fire regime and moderate grazing, at least in years following burns. Severe destabilization of the dunes, e.g., from off-road vehicle use, could also threaten its habitat.
Threats or Limiting Factors
Studies have shown that Painted milkvetch occurs in early successional habitats that are maintained by grazing or fire. Threats would include any process or action that hinders or prevents grazing or fire. Plants occur in habitats where the potential for off-road recreational vehicles use is real; however, actual use has not been documented at any known occurrence. Invasive plants are a potential threat to its habitat though current assessments on the condition of occupied habitats have not been made.
- Literature Cited AboveLegend: View Online Publication
- Barneby, R.C. 1964. Atlas of North American Astragalus. 2 Vols. New York Botanical Garden, Bronx, New York. 1188 pp.
- Lesica, P., M. T. Lavin, and P. F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p.
- Martin, B., S. Cooper, B. Heidel, T. Hildebrand, G. Jones, D. Lenz, and P. Lesica. 1998. Natural community inventory within landscapes in the Northern Great Plains Steppe Ecoregion of the United States. Unpublished report to the Natural Resource Conservation Service, Northern Plains Regional Office. The Nature Conservancy, Montana Field Office, Helena. 211pp.
- McGregor, R.L., coordinator, and T.M. Barkley, R.E. Brooks, and E.K. Schofield, eds.: Great Plains Flora Association. 1986. Flora of the Great Plains. Lawrence, KS: Univ. Press Kansas. 1392 pp.