Sericocarpus rigidus

Aster curtus Cronquist:
China (Asia)
United States (North America)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: Regional endemic: southwest British Columbia (restricted to souther Vancouver Island), Puget Trough in Washington and Willamette Valley, Oregon.

Plants 19–37 cm. Stems erect, puberulent. Leaves basal and proxi-malmost cauline withering by flowering; cauline sessile; blades obovate, 10–60 × 3–9 mm, margins entire, apices acute, distal acuminate, faces puberulent. Heads 2–3 per branch, in compact corymbi-form arrays. Peduncle bracts ovate, puberulent. Involucres 6–9 mm. Phyllaries in 3–4 series, outer 3–5 mm, mid 5–7 mm, puberulent. Ray florets 1–2; corolla tubes 2–4 mm, laminae 2–3 mm. Disc florets 9–17; corolla tubes 4–6 mm, lobes 0.6–1 mm. Ovaries fusiform-obconic, 1–2 mm, strigose; pappi: inner series 6–7 mm.

Aster curtus Cronquist

This species is separated from the closely related Aster oregonensis by small ray flowers shorter than the pappus, fewer flower heads, and generally smaller stature (Oregon Natural Heritage Program).

Comments: Occurs in open grassland habitats in the Willamette-Puget Trough. A majority of the occurrences occur in gravelly, glacial outwash soils. However, in the southern and northern portions of its range, it occurs in the clayey and exposed bedrock habitats, respectively. The general requirement appears to be open, non-forested habitats that are seasonally mesic but somewhat moisture stressed during late summer. Trees such as Quercus garryana and Arbutus menziesii are often present, but do not form a closey overstory. Possible associates of the understory of shrubs are Cytisus scoparius, Holodiscus discolor, and Symphoricarpos albus. Dense thickets are not formed by these shrubs because soils are too shallow. The ground tends to be dominated by a mixture of introduced grasses including Aira praecox, Dactylis glomerata, Poa sp., Cynosurus echinatus and Anthoxanthum odoratum (Douglas 1994).

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 21 - 300

Comments: There are approximately 50 known occurrences in Washington, another 28 in Oregon, and another 22 in British Columbia. Douglas and Illingworth (1994) report eighteen occurrences, six of which are likely extirpated.

Occurs primarily in open grassland habitats. Population levels and vigor decline as a canopy of trees or shrubs develops. Seedlings appear to be poor competitors.

The taxon appears to rely primarily upon asexual reproduction, through framentation of existing clones and repeated production of new ramets.

Canada

Rounded National Status Rank: N2 - Imperiled

United States

Rounded National Status Rank: N3 - Vulnerable

Rounded Global Status Rank: G3 - Vulnerable

Reasons: Approximately 80 total element occurrences. However, the number of discrete, isolated populations is somewhat less, and the degree to which many of the occurrences are threatened is significant. Threats include invasion of its habitat by native conifers and non-native shrubs and grasses, as well as development, grazing, and military training exercises.

Global Short Term Trend: Decline of 10-30%

Comments: Small occurrences continue to be lost to development and/or conifer and non-native invasions. Large occurrences are also being degraded by the same invasions.

Comments: The most significant threat to this taxon is the invasion of its habitat by native conifers and non-native shrubs (Scot's broom) and grasses. Other significant threats include the continued loss of habitat due to suburban and light industrial development, grazing, off-road vehicle use, and military training exercises. Fire suppression appears to have favored the expansion of some native species including Symphoricarpos albus which may also competitively exclude this species from existing sites or prevent its establishment at new sites (Douglas 1994).