White Snakeroot with Whorled (3) Leaf Arrangement

Photo of White Snakeroot (Ageratina altissima)

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Taken on May. 8, 2015

Ageratina altissima is usually described as having an opposite leaf arrangement, and it does on most plants. However, it can also have a whorled leaf arrangement; usually, whorled leaves in sets of three, as pictured here, are the second most common arrangement. Such arrangements are still uncommon.

This variability may reflect or be related to this species' membership in the broader Eupatorieae tribe, which contains numerous other species, Eutrochium sp. being conspicuous examples, which tend to have whorled leaf arrangements.

This was a wild plant that came up as a weed in a bed of spearmint. It probably spread from a population in the wooded area above the garages just uphill from this site. This species is abundant in this neighborhood.