Symphyotrichum prenanthoides (Crooked Aster)

Plant Info
Also known as: Crooked-stem Aster, Zig-zag Aster
Family:Asteraceae (Aster)
Life cycle:perennial
Habitat:part shade, sun; moist soil;
Bloom season:August - October
Plant height:1 to 3 feet
Wetland Indicator Status:GP: none MW: FAC NCNE: FAC
MN county distribution (click map to enlarge):Minnesota county distribution map
National distribution (click map to enlarge):National distribution map

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Detailed Information

Flower: Flower shape: 7+petals Cluster type: panicle

[photo of flowers] Branching clusters of stalked flowers at the top of the stem and arising from upper leaf axils. Flowers are about 1 inch across with 20 to 35 petals (ray flowers) and a yellow center disk that turns reddish with age. Ray color is very pale lavender (nearly white) to light blue-violet.

[photo of bracts (phyllaries)] The bracts (phyllaries) surrounding the base of the flower are in 4 to 6 layers, lance-oblong to linear, light green with a lance to elongated diamond-shaped darker green tip that is appressed or spreading. Phyllaries are hairless except for a few minute hairs around the tip edge. Flower stalks are up to ¾ inch long, hairy in lines, with several leaf-like bracts below the flower.

Leaves and stems: Leaf attachment: alternate Leaf attachment: basal Leaf type: simple

[photo of lower/mid stem leaves] Leaves are mostly lance/spear/spatula-shaped, the blade coarsely toothed, sharply pointed at the tip, abruptly narrowed at the base to a toothless, broadly winged stalk that is slightly enlarged at the base into a pair of lobes (auricles) that clasp the stem. Leaves are hairless except for a few hairs on the midvein on the underside. Basal leaves have slender, narrowly winged stalks and wither away by flowering time along with the lowest stem leaves. Most stem leaves persist through fruiting.

[photo of upper stem and leaves] In the upper stem, leaves quickly change shape, become stalkless and more generally lance-shaped but still auricled and clasping, becoming smaller and toothless or nearly so as they ascend the stem, with the uppermost leaves reduced to bracts. Stems are mostly single, sometimes multiple from the base, ascending to erect but may be floppy in the upper plant, green or purple, hairless on the lower stem and hairy in lines in the upper plant. Stems often zig-zag between the leaf nodes, hence the common names. Plants may form colonies from creeping rhizomes.

Fruit: Fruit type: seed with plume

Fruit is a dry seed with a tuft of light brown hair to carry it off in the wind.


The leaf shape of Crooked Aster is pretty unique and makes it easy to identify in the field. While Big-leaf Aster (Eurybia macrophylla) also has light blue-violet flowers and broadly winged leaf stalks that clasp the stem, its leaves are much broader and variable in shape as they ascend the stem, most with heart-shaped bases.

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More photos

Photos by K. Chayka and Peter M. Dziuk taken at Whitewater Wildlife Management Area and Whitewater State Park, Winona County.


Have you seen this plant in Minnesota, or have any other comments about it?

Posted by: Joseph C - Knife Lake, Kanabec Co
on: 2017-09-01 11:51:06

Along the path to the lake

Posted by: Frank@Mound - Maple Plain
on: 2022-02-05 16:31:55

For awhile I was thinking it was Purple=Stemmed due to its purple stem, I am not thinking it is Crooked. The leaf is right and the ray count is what made me look further. These have begun popping up around my place in the last two years. Outside of the range, but....

Posted by: K. Chayka
on: 2022-02-05 16:47:45

Frank, the flowers of most blue-violet asters are very similar but the leaves of S. prenanthoides are really distinctive and should be the best way to distinguish it. Eurybia macrophylla (big-leaf aster), which is more common in the state, can also have broad wings on leaves but its leaves are much broader and more heart-shaped. S. ciliolatum (Lindley's aster) also has winged leaves but the wings are much narrower than S. prenanthoides.

Posted by: Frank@Mound - Maple Plain
on: 2022-02-16 11:33:07

Sorry, there was a typo in my comment. It should have read "I am NOW thinking it is Crooked" (as opposed to Purple Stem. Big Leaf appears to me a completely different type of aster, and a woodland one. These are growing in part to full sun, in a shallow drainage of compacted clay and sand (over my french tile). I'll post to FB when the season of growth comes upon us to confirm.

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