Published by Brian Wagner on 10/28/25 in “Growing Flowers from Seed.”
Symphyotrichum pilosum (commonly called hairy aster), previously named Aster pilosum, is an Asteraceae herbaceous perennial native to the eastern United States and southern Ontario. It is often called ‘Hairy Oldfield Aster’ because it springs up in abandoned fields, especially if they’ve been abandoned. It has a profuse number of small white daisy-like flowers – absolutely smothering the plant.
It is hardy to Zone 3 and is tough as nails. It will produce an exorbitant amount of seed, enough to populate an entire community from one single plant – but will bring a soft smile when it flowers in early autumn. In its native geography it is happiest growing along the forest edge and also in open fields where it receives full sun. Not a plant for the shade, this perennial will be happy if neglected with a moderate amount of sun – but will thrive if given all the goodness it can get.
Growing from Seed
Hairy Aster has some interesting properties. First, freshly harvested seeds have a conditional dormancy meaning that they’ll only germinate under very specific conditions. In the case of Hairy Aster, they will only germinate at very high temperatures (around 35C or 95F) and with very bright light (Baskin and Baskin, 1979). If propagating from fresh seed, you don’t need to cold stratify the seeds if you can give them these high temperatures and light.
They have a type of dormancy called a Type 2 non-deep physiological dormancy. Basically, the dormancy is quite weak – and the seeds will become non-dormant over time, especially if you just leave them on the mother plant and harvest them after winter. Good trick. It’s a “type 2” because they can only germinate at high temps when fresh, but after cold stratification or after-ripening they can germinate at much lower temperatures if desired.
To break dormancy and propagate seeds, either cook ‘em under bright lights (as per above) – or cold stratify them for 12 weeks at 4C (40F). Also interesting fact, if you can somehow cold stratify with ambient light during the day, they retain their ability to germinate in darkness later on. Otherwise, if you keep them in a dark fridge they get pushed into skotodormancy and they absolutely require light to germinate after. No biggee.
Seeds will germinate in 5 or 6 days, and you’ll be off to the races. Perhaps you’ll regret growing them given the self-seeding habit, but your neighbours might thank you.
References
Baskin JM, Baskin CC. The light requirement for germination of Aster pilosus seeds: temporal aspects and ecological consequences. The Journal of Ecology. 1985 Nov 1:765-73.
Baskin JM, Baskin CC. The germination strategy of oldfield aster (Aster pilosus). American Journal of Botany. 1979 Jan;66(1):1-5.
Baskin CC, Baskin JM. Seeds: Ecology, Biogeography, and Evolution of Dormancy and Germination. Second Edition. 2014. Academic Press: San Diego, California
Jones AG. Observations on reproduction and phenology in some perennial asters. American Midland Naturalist. 1978 Jan 1:184-97.
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Fitch EA, Walck JL, Hidayati SN. Temporal fulfilment of the light requirement for seed germination: an example of its use in management of rare species. InSeeds: biology, development and ecology. Proceedings of the Eighth International Workshop on Seeds, Brisbane, Australia, May 2005 2007 (pp. 365-373). Wallingford UK: CABI.
Baskin CC, Baskin JM. Germination ecophysiology of herbaceous plant species in a temperate region. American Journal of Botany. 1988 Feb;75(2):286-305.
Goloff Jr AA, Bazzaz FA. A germination model for natural seed populations. Journal of Theoretical Biology. 1975 Aug 1;52(2):259-83.
Peterson DL, Bazzaz FA. Life cycle characteristics of Aster pilosus in early succesional habitats. Ecology. 1978 Aug;59(5):1005-13.
Prinzie TP, Chmielewski JG. Significance of achene characteristics and within‐achene resource allocation in the germination strategy of tetraploid Aster pilosus var. pilosus (Asteraceae). American Journal of Botany. 1994 Mar;81(3):259-64.
Keever C. Causes of succession on old fields of the Piedmont, North Carolina. Ecological Monographs. 1950 Jul 1;20(3):229-50.
Chmielewski JG, Semple JC. The biology of Canadian weeds. 114. Symphyotrichum pilosum (Willd.) Nesom (Aster pilosus Willd.). Canadian Journal of Plant Science. 2001 Oct 1;81(4):851-65.
Lee IY, Kim SH, Lee YH, Pradeep A, Hong SH. Occurrence and Management of an Invasive Plant in Korea: Symphyotrichum pilosum. Weed & Turfgrass Science. 2023;12(4):353-63.