Symphyotrichum shortii (Lindl.) Nesom
Basis for Listing
Symphyotrichum shortii (Short’s aster) is a typical, though not always common, aster of deciduous forests in eastern parts of the country. In fact, it is considered of conservation concern along the whole periphery of its range (Brouillet et al. 2006). It reaches Minnesota at the extreme northwestern limit of its range and is restricted to remnant forests in the southeastern corner of the state (Paleozoic Plateau Section).
It was designated a threatened species in Minnesota in 1996, at which time it was known from a small number of sites. Since then, it has been found at enough additional locations to indicate it is not as rare as previously thought, and threatened status is no longer necessary. However, because its habitat is under pressure from residential development, livestock grazing, timber harvest, and invasive species it was retained on the list in 2013, with a status of special concern.
Symphyotrichum shortii grows to a height of 30–150 cm (1-5 ft.). The lower portions of the stem are smooth; the upper portions have dense short hairs. It has only a short rhizome and does not spread underground. The leaves are short-hairy on the lower surfaces and smooth on the upper. The basal leaves have petioles that are 1–2 times as long as blades, but they wither by flowering time. The stem leaves are mostly persistent and have slender petioles, which get progressively shorter the farther up the stem. The blades of the stem leaves are ovate to lanceolate in shape, with cordate to truncate or rounded bases. The phyllaries of the flowers are in 4–5(–6) series, lanceolate or linear-lanceolate, and strongly unequal in length. The ray florets are usually blue or purple-blue, seldom pinkish or white (Brouillet et al. 2006).
Symphyotrichum shortii is a rather showy blue-flowered aster. It bears a superficial resemblance to the common S. oolentangiense (sky blue aster), for which it might be mistaken in the field. However, only the lower leaves of S. oolentangiense are cordate or subcordate, while nearly all leaves below the inflorescence in S. shortii are cordate or subcordate, the lower stem leaves usually deeply so.
Symphyotrichum shortii appears to prefer mesic to dry-mesic forested slopes and level terrain dominated by Quercus alba (white oak), Q. rubra (northern red oak), Acer saccharum (sugar maple), and Tilia americana (basswood). Symphyotrichum shortii typically grows in somewhat closed canopy forests or in gaps where partial sunlight reaches the forest floor. Populations typically occur as scattered individuals, though at times the species may be locally abundant. Several sites seem to be associated with a transition from silty colluvial soils to slightly coarser soils part way up wooded slopes. It is not yet clear whether this apparent microhabitat preference is related to soil conditions themselves or to possible changes in light that occur along the slope, as maple forest gives way to oak.
Biology / Life History
Very little is known about the specific biology of S. shortii. It is known to be a moderately long-lived insect-pollinated perennial, which reproduces only by seed. The seeds are likely dispersed by wind and secondarily by small animals, though dispersal distances are probably not great. Under ideal conditions, S. shortii may reach reproductive status the second year following germination, but harsh conditions can delay maturation. Once reproductive maturity has been reached, S. shortii will likely flower each year, unless damaged by animal predation or extreme weather conditions.
Conservation / Management
Potential threats from changes in land use are not well understood. It is clear that severe habitat damage, which follows activities such as logging and livestock grazing, are deleterious and likely fatal to populations of this species. However, it is not possible to quantify the threshold beyond which this species would experience irrevocable decline. It should be noted, however, that few viable populations have been found in habitats with a history of severe disturbance.
Best Time to Search
The best time to search for S. shortii is September through October. Because it flowers late in the season, it might be overlooked in mid-summer searches.
Conservation Efforts in Minnesota
There are a few sites of S. shortii on State Forest lands, which does afford protection from commercial or residential development projects and livestock grazing, but the sites are actively managed for timber production, which could be problematic for the species.
References and Additional Information
Brouillet, L., J. C. Semple, G. A. Allen, K. L. Chambers, and S. D. Sundberg. 2006. Symphyotrichum. Pages 465-539 in Flora of North America Editorial Committee, editors. Flora of North America north of Mexico. Volume 20. Oxford University Press, New York, New York.
Coffin, B., and L. Pfannmuller, editors. 1988. Minnesota's endangered flora and fauna. University of Minnesota Press, Minneapolis. 473 pp.
Gleason, H. A., and A. Cronquist. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. Second Edition. New York Botanical Garden, Bronx, New York. 910 pp.
Minnesota County Biological Survey. 1994. Natural communities and rare species of Houston County. Minnesota County Biological Survey Biological Report No. 50. Minnesota Department of Natural Resources, St. Paul.
Minnesota Department of Natural Resources. 2005. Field guide to the native plant communities of Minnesota: the eastern broadleaf forest province. Ecological Land Classification Program, Minnesota County Biological Survey, and Natural Heritage and Nongame Research Program. Minnesota Department of Natural Resources, St. Paul, Minnesota. 394 pp.
Minnesota Department of Natural Resources, Division of Ecological Resources. 2008. Rare species guide: an online encyclopedia of Minnesota's rare native plants and animals [Web Application]. Minnesota Department of Natural Resources, St. Paul, Minnesota. Accessed 1 July 2009.
Minnesota Department of Natural Resources, Division of Fish and Wildlife. 1995. Statement of need and reasonableness in the matter of proposed amendment of Minnesota Rules, Chapter 6134: endangered and threatened species. Minnesota Department of Natural Resources, St. Paul, Minnesota. 336 pp.
Ownbey, G. B., and T. Morley. 1991. Vascular plants of Minnesota: a checklist and atlas. University of Minnesota Press, Minneapolis. 320 pp.
Rosendahl, C. O., and J. W. Moore. 1947. A new variety of Sedum rosea from southeastern Minnesota and additional notes on the flora of the region. Rhodora 49:197-202.
Semple, J. C., and J. G. Chmielewski. 1983. Aster shortii. In G. W. Argus and D. J. White, editors. Atlas of the rare vascular plants of Ontario. National Museums of Canada, Ottawa, Ontario, Canada.
Skinner, L. H. 1941. Aster in Wisconsin. American Midland Naturalist 26:399-420.