Until today, I always thought of ageratum as a low-growing garden annual that you could buy readily in any garden center– but I never knew it was also a native wildflower!
I recently found a colony of these plants growing along the side of a shallow pond in Blacksburg, VA. The plants were tall and distinctly “minty” looking, but they lacked the square stem of the mint family… The bluish-purple flowers screamed AGERATUM, but I thought–no way! But what IS it? I made a note to myself to “look up this wild ageratum” as soon as I got home. Sure enough, I found this very accurate description online:
Blue mist flower, or wild ageratum is a perennial wildflower that can reach up to 3 feet in height. The leaves are opposite, hairy, ovoid, toothed and have short petioles. The blue to purple flowers occur in flat-topped clusters at the top of the stem. The clusters can be several inches across in width. Mist flower plants arise from a dense system of underground rhizomes, so they can be mildly weedy if introduced to the home garden.
Mist flower grows in full sun. The plant prefers WET conditions like those found near shallow ponds and soggy meadows. Bloom time is late summer to early fall.
Well there you have it! The ancestor to our common garden annual is an August-blooming, wetland-loving native wildflower! Wild ageratum is blue mist flower.
Note: I later found wild ageratum growing along the New River in Giles County. The plants formed large “drifts” of color along the river banks in mid-August.