Asters of Wisconsin
Family: Asteraceae (formerly Compositae)

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There are a total of 30 Asters known for Wisconsin, 29 in the genus Aster plus Brachyactis ciliata (Ledeb.) Ledeb., once known as Aster brachyactis. Leaves, including basal leaves are often important key characters, as are the phyllaries. As always, it is important to record the live color of the ray flowers and carefully considered habitat descriptions can be very helpful. Collectors are encouraged to select representative specimens and to be sure to take the full stem with all leaves, resisting the urge to make pressing of these often tall plants easier by collecting only the tops. Some Aster species are highly variable and there seems to be a tendency among experts to assign hybrid status, often on the basis of perceived intermediate characters.

In the recently published Volume 20 of the Flora of North America, the plants previously included in the genus Aster are reassigned to several other genera, in keeping with current taxonomic research. The excellent Keys to all the Wisconsin species of the Aster family, by Robert R. Kowal (available on the UW-Stevens Point web site) includes the asters, with names reflecting the new nomenclature.

The treatment of Wisconsin asters by Shinners (1941) although a bit out of date in terms of nomenclature is an important publication, as is the treatment of Asters by Voss (1996) in Michigan Flora, Vol. III. Shinners key does not include Brachyactis ciliata, which may prove difficult to recognize as an Aster at first encounter, because the heads are totally lacking ray flowers--the only Aster in Wisconsin with this condition.

The key to Asters in Michigan Flora, vol. 3 is very helpful and relevant. Most of the common, widespread Wisconsin species are included in the Michigan key, except for A. firmus which is treated as a variety of A. puniceus (see below). The following Wisconsin species are not included in the key to Michigan asters and are mostly either rare or local in distribution, often primarily in the southwestern portion of the state.

  • Aster drummondii. Considered by some authors to be a variety of A. sagittifolius. Not deemed to be present in Michigan, but discussed under A. sagittifolius in Michigan Flora.
  • A. falcatus. Rare.
  • A. firmus. Treated in Michigan keys as a variety of A. puniceus and sometimes treated as A. lucidulus (A. Gray) Wiegand in other books.
  • A. fragilis.
  • A. hesperius.
  • A. linariifolius. Mostly southwest and southcentral Wisconsin.
  • A. oblongifolius. Primarily SW.
  • A. prenanthoides. Mostly local, SW and central.

The following species of Aster are included in the Michigan key, but are not found in Wisconsin:

  • Aster modestus. A boreal species ranging south only into far northern upper peninsula of Michigan.
  • A. nemoralis. Reported in Michigan in the eastern upper peninsula on wet sites, especially fens.
  • A. paternus. Known from a single site in Michigan and ranging to the east and south, therefore not likely in Wisconsin.
  • A. solidagineus. No Wisconsin records.
  • A. subulatus. A halophyte reported only from 2 sites in southeastern lower Michigan, but probably spreading along highways. This species may well appear in Wisconsin in the near future and may be expected along the edge of heavily salted roads. The leaves are broader than Brachyactis ciliata and there are very small blue rays.
  • A. tataricus. A garden escape known from a single site in southern lower Michigan.

Literature cited:

Voss, Edward G. (1996). Michigan flora, vol. III. Cranbrook Institute of Science, Bulletin 61 and Univ. Michigan Herbarium.

Shinners, L.H. 1941. The Genus Aster in Wisconsin. Am. Midl. Natl. 26:398-420.


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