Common Hoptree

Ptelea trifoliata is a small native deciduous tree or large shrub in the citrus family (Rutaceae), reaching 15–25 ft tall. Native to woodlands, thickets, and rocky slopes from Ontario south to Florida and west to Texas, it produces trifoliate leaves, clusters of small greenish-white flowers in late spring, and papery disk-shaped samaras that persist through winter. It is the primary larval host plant of the giant swallowtail butterfly (Papilio cresphontes) across much of eastern North America, giving it high wildlife value in native plantings.

It grows naturally as an understory species and tolerates part shade, though it sets heavier fruit crops with more direct light. Plants adapt to dry, rocky, and limestone-rich soils and become drought tolerant once established. Bark, leaves, and fruit emit a pungent citrus-skunk odor when bruised - the source of common names stinking ash and skunk bush. It can be trained to a single trunk or left to develop as a multi-stemmed shrub; persistent samaras attract finches and other seed-eating birds into winter.

Several Native American nations used root bark preparations as a digestive tonic and fever remedy. The samaras were historically used as a substitute for hops in beer, which accounts for the name hoptree. The plant contains quinoline alkaloids and furocoumarins, some of which have demonstrated antimicrobial activity in laboratory studies.