Ageratina altissima (White Snakeroot)
|Also known as:|
|Habitat:||part shade, shade; thickets, deciduous woods|
|Bloom season:||July - October|
|Plant height:||1 to 4 feet|
|Wetland Indicator Status:||GP: UPL MW: FACU NCNE: FACU|
|MN county distribution (click map to enlarge):|
|National distribution (click map to enlarge):|
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A few to many small flower heads in numerous flat clusters 1 to 2 inches across at the end of branching stems. Flower heads are made up of 10 or more bright white 5-parted disk flowers, each about 1/6 inch across, with protruding white styles. There are no ray flowers (petals).
Leaves are 2 to 6 inches long, 1 to 4 inches wide with coarse teeth all around the edges, a sharply pointed tip, and slender leaf stalk up to 2½ inches long. The leaf base is typically wide and rounded or somewhat heart-shaped, becoming more tapered as they ascend the stem. The underside of leaves are typically hairy along major veins. Stems are green and mostly hairless.
Notes:When I took a walk through the park in mid-September, the woods there were filled with White Snakeroot. It and Canada Goldenrod were about the only things blooming in the woods. The flowers are similar to Boneset, and in fact White Snakeroot used to be in the same genus (Eupatorium rugosum) but has since been reclassified. The leaves are distinctly different between the Eupatorium species and White Snakeroot, so a positive ID is fairly easy.
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Photos by K. Chayka taken at Long Lake Regional Park, New Brighton, MN, July and September 2006 and August 2009. Other Photos courtesy Peter M. Dziuk taken in Anoka county.
Have you seen this plant in Minnesota, or have any other comments about it?