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Wisconsin Plant of the Week

Aster prenanthoides Muhl. ex Willd.

Asteraceae (Aster or Sunflower Family)

Common Name:

crooked-stem aster


The genus Aster in the broad sense has several hundred species worldwide, that grow in many different habitats, all with a similar flower structure.  Like the “flowers” of sunflowers, aster “flowers” are made up of sterile ray flowers -- what look like petals-- and fertile disc flowers that eventually produce the seeds.  WI has nearly 30 Aster species, many of which hybridize with each other for over 90 different (but not always easily recognized) taxa.

Crooked aster, in the group of Aster native to North America, is a perennial that grows from a rhizome in low woods and moist thickets where there’s been little disturbance.  It prefers neutral to slightly acidic soil where organic matter has accumulated and with little sediment deposition.   

Crooked aster is most easily recognized by its unusual leaves -- the base of each leaf wraps around the stem, the lower third of each leaf is narrowed with a smooth edge, and the rest is wider with coarse teeth and a long pointed tip.

Flowers bloom from August through October with heads about 3 cm across in loose clusters. Disc flowers are yellow and the ray flowers range from blue or pale purple to white, the latter more common in the southeast.

The stems are branched only in the top third of the plant. In spite of the common name, the stem is only slightly zigzag or crooked. Unlike similar more common asters found in wetlands, crooked aster is not clonal and so the plants don’t form dense patches.

  • Origin of the name: Aster, L., a star; prenans, Gk., drooping
  • Range:  Eastern N. Amer., s. to IA, VA, in the mountains to TN
  • WI Range:  Statewide, less common in the northeast
  • Common associates: lake sedge, water hemlock, green ash
  • Wetland Indicator Status: FAC
  • Coefficient of Conservatism: WI, 9; MI, not listed; Chicago Region, 10
  • Related Links: Wisconsin State Herbarium
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