Description

Ageratina altissima grows up to 4' tall. It is a clumping plant that produces more stems as it matures. Terminal clusters of abundant, small, white flowers appear in late summer, and can persist until frost.

Cultivation

Very easy to cultivate in a variety of soils and light conditions. It is drought tolerant, but foliage and blooms will decline earlier in a sunny, or dry location. It will slowly spread by rhyzomes, or more aggressively from seed. Ideal to naturalize in moist open locations. A good choice for cottage, and rock gardens, though it is recommended to remove spend flowers before they go to seed, to avoid unwanted spread. Flowers persist late in the season, when very little else is in bloom; July to October. Zones 2-8

Propagation

Self seeds readily. Clumps can be divided in early spring. Plants have taproots. This makes them drought tolerant, but hard to dig out, particularly in heavy clay.

Additional Notes

The common name "snakeroot" is a reference to the early belief that the roots where a cure for snakebite. In fact all parts of the plant are highly toxic and can be fatal to animals and humans if ingested in large quantities. It was later discovered that these toxins are passed on to humans through cow's milk, causing "milk sickness". Fortunately, grazers avoid this plant and only forage on it as a last resort. Ageratina altissima was previously classified as Eupatorium rugosum.