About Eupatorium hyssopifolium L.
Eupatorium hyssopifolium, commonly known as hyssopleaf thoroughwort, is a fall-blooming herbaceous plant native to North America. Like other members of the genus Eupatorium, it produces inflorescences that hold a large number of very small flower heads. Each flower head has 5 white disc florets and no ray florets. It reaches a height of 0.5 to 1 meter (20 to 40 inches), which is toward the shorter end of the height range seen in Eupatorium species. Individuals classified as E. hyssopifolium can be either diploid or polyploid, and some appear to have originated from past hybridizations with Eupatorium serotinum. Hybrids with E. album and E. linearifolium are also thought to exist. The hybrid E. torreyanum is similar in appearance to E. hyssopifolium, but it is actually a cross between E. serotinum and Eupatorium mohrii. Two varieties of Eupatorium hyssopifolium are recognized: Eupatorium hyssopifolium var. hyssopifolium, which has leaves 2–5 mm wide, and Eupatorium hyssopifolium var. laciniatum A.Gray, which has leaves 5–15 mm wide. Eupatorium hyssopifolium is distributed across most of the eastern and south-central United States, ranging from Massachusetts west to Wisconsin, and as far south as Texas and Florida. It is listed as endangered in the state of Ohio. It grows in moist soils, and can be found in woodlands, oak savannas, pastures, fields, roadsides, and disturbed areas, growing on both acidic and calcareous substrates. Ecologically, Eupatorium hyssopifolium becomes more abundant after fire disturbance, and is most common in habitats with short fire return intervals. For human use, Eupatorium hyssopifolium can be used medicinally when applied externally to treat insect and reptile bites. It can also be planted near crops to attract beneficial insects.
