05/24/2026
Thanks Nancy F for bringing this to our attention!
Why is Gregg’s mistflower (Conoclinium dissectum) so irresistible to monarchs and queens? This is one of a few species of plants that produces a natural compound called intermedine, which is a pyrrolizidine alkaloid (PA for short). PA’s occur in many plants and are well known to ranchers, being poisonous to livestock (and humans) as they serve to protect the plants from grazing. However, it turns out that intermedine isn’t poisonous to butterflies, and is essential to the reproduction of queens and monarchs. When you see them nectaring on Gregg’s mistflower, over 90% of them are males happily imbibing intermedine with the nectar. Then they convert part of the intermedine to a smaller molecule named danaidone which is a s*x attractant pheromone that draws in the females. During mating, the male passes the remaining unchanged intermedine to the female as a “nuptial gift” that once again manifests itself as a toxin, this time rendering her eggs unpalatable to predators! Thus as the butterfly pollinates the flower, the flower provides a molecule that in two ways enables the butterfly to reproduce! Gregg’s mistflower is a spreading perennial growing about 2’ tall and spreading 3’ or more which spreads almost like a mint plant. Blue flowers appear throughout the warm season. Grow in full to part sun, provide regular water—this is a riparian species. This plant is root hardy to at least 0° F (cut back if frosted or when plants are leggy, often after blooming cycle). Flowers provide nectar for a large host of pollinators, and can be covered in butterflies. There are many plants called “mistflowers” in various genera. This plant was formerly known as Eupatorium greggii or Conoclinium greggii.
Waterways, depressions, washes and ditches, dry sandy or rocky soil, and in mesquite bosque at about 1300-4600 ft. in southern Arizona, New Mexico, Texas, south into central Mexico.
