About 15 summers ago, while Jim and I were still attempting to tame a very large, messy, and wildly overgrown daylily garden, I discovered a pretty plant in the daylily beds with fuzzy lavender-blue flowers and a sweet fragrance reminiscent of baby powder. I identified the plant as the annual ageratum, only it wasn’t.

It was the perennial version, Conoclinium coelestinum, formerly known as Eupatorium coelestinum. Its common name is Blue mistflower. This hairy-stemmed native to the central and southeastern United States is common in the Coastal Plain and Piedmont regions. With a liking for moist to wet soils, mistflower is found in old farm fields, meadows, and disturbed sites. The purplish stems bear ovoid, coarsely serrated, bright green leaves and tiny, fluffy flowers that attract butterflies.

Mistflower grows to 1½ to 3 feet in height with a similar spread without any major disease or insect problems other than downy mildew or leaf miners and aphids. This perennial requires a...