- Scientific name: Symphyotrichum praealtum (Poir.) G.L.Nesom
- Species of Greatest Conservation Need (MA State Wildlife Action Plan)
Description
Willow aster is a perennial, colonial species with long rhizomes. The mature plants may grow to 2 m (6.5 feet), and it blooms in late summer. Willow aster has thick, firm willow-like leaves, conspicuously reticulate beneath with isodiametric areolae (rounded equal areas defined by the veinlets) on the leaf’s underside. Flowers (rays) are usually light blue, though may be white on occasion. The plant may be glabrous or have some pubescence in vertical lines on the stems.
Life cycle and behavior
This is a perennial species that blooms from mid-August through September. Mature achenes are present October to mid-November. As an aster, it is pollinated by a variety of insects seeking food late in the year. Similar to other asters, its seeds are wind-dispersed.
Population status
Willow-leaved aster is a species of greatest conservation need and is maintained on the plant watch list. One population of this species has recently been verified in Berkshire County. In the past (pre-1900), this species was observed in Suffolk County in eastern Massachusetts and was considered historic in the state until 2013.
Distribution and abundance
Willow-leaved aster range extends from New Brunswick (where it is considered introduced) and Ontario south to New Mexico, Texas east to Florida, excluding Delaware and South Carolina. It is considered critically imperiled in Massachusetts, Delaware, Virginia, Tennessee, and Georgia; imperiled in Ontario; and vulnerable in Michigan and West Virginia.
Habitat
Gleason and Cronquist (1991) state the species habitat is moist, low ground. The current population in Massachusetts occurs on state-owned land in fields that are mown approximately every three years to keep them open.
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Threats
Invasive plant species such as multiflora rose, Asiatic bittersweet and non-native shrub honeysuckles threaten to shade out the population, despite efforts to remove them. This plant could be easily mistaken for the more common S. lanceolatum, and thus not protected but cut or removed.
Conservation
The exact ecological needs of willow-leaved aster are not known. However, maintaining high quality habitat is essential. The known population of this species is mown every few years, but there are a number of aggressive invasive plant species growing with the population. Control of these invasive species to ensure survival of this rare aster as part of the state's biodiversity is important. Research is needed to determine whether this plant can be grown in a nursery or garden setting for purposes of species restoration. Questions about seed germination and seed storage over winter will need to be answered. In addition, sites with appropriate habitat and management regime will need to be identified.
References
Fernald, M.L. 1970. Gray’s Manual of Botany, Eighth (Centennial) Edition - Illustrated. D.Van Nostrand Company. New York.
Gleason, H.A., and A. Cronquist. 1991. Manual of Vascular Plants of Northeastern United States and Adjacent Canada, Second Edition. The New York Botanical Garden, Bronx, New York.
Haines, A. 2011. Flora Novae Angliae. The New England Wild Flower Society. Yale University Press, New Haven, CT.
Native Plant Trust. 2014. NORM Phenology Information.
NatureServe. 2025. NatureServe Network Biodiversity Location Data accessed through NatureServe Explorer [web application]. NatureServe, Arlington, Virginia. Available https://explorer.natureserve.org/. Accessed: 5/5/2025.
Contact
| Date published: | May 7, 2025 |
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