Pottery Milkvetch - Astragalus ceramicus
State Rank Reason (see State Rank above)
Astragalus ceramicus is found in Beaverhead County and in the eastern-most counties of Montana. Populations represent two varieties which together are known from about 25 occurrences observed between 1903 and 2005. Plants grow in sand, very sandy soil of sandhills, or below sandstone outcrops which in Montana represent specialized habitats. Most sites have not been revisited since the 1980s to 1990s; therefore, current data on locations, population sizes, and threats is greatly needed.
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Pottery Milkvetch (Astragalus ceramicus) 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, which are profiled separately in the Plant Field Guide.
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). At least half of its year’s growth can remain concealed in sand (Barneby 1964). Stems often grow a long distance from their rootstock, and most herbarium specimens are not of the full plant (Barneby 1964). Its pods (fruits) are balloon-shaped, large, and red-mottled.
Southeast (Beaverhead County) and eastern MT and the western Dakotas south to AZ, NM, and TX; most common in the sandhill region of Nebraska (Kartesz 2009; McGregor 1986, Flora of the Great Plains). It is confined to sand dunes and areas where loose sand predominates (Barneby 1964). In the arid west occurrences are widely distributed and can be locally abundant, yet the species is not common (Barneby 1964).
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).
Threats or Limiting Factors
Studies have shown that Pottery 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.
- 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.