Ptelea trifoliata, commonly known as common hoptree, wafer ash, stinking ash, and skunk bush, is a species of flowering plant in the citrus family (Rutaceae). It is native to North America, where it is found in Canada, Mexico, and the United States. It is a deciduous shrub or tree, with alternate, trifoliate leaves. Description Ptelea trifoliata is a small tree, or often a shrub of a few spreading stems, growing to around tall with a broad crown. The bark is reddish brown to gray brown, with short horizontal lenticels (warty corky ridges), becoming slightly scaly, The plant has an unpleasant odor and bitter taste. Branchlets are dark reddish brown, shining, covered with small excrescences. The twigs are slender to moderately stout, brown with deep U-shaped leaf scars, and with short, light brown, fuzzy buds. It has thick fleshy roots. Leaves Its leaves are alternate and compound with three leaflets, dotted with oil glands. The leaflets are sessile, ovate or oblong, long by broad, pointed at the base, entire or serrate, and gradually pointed at the apex. They are feather-veined, with a prominent midrib and primary veins. They come out of the bud conduplicate and very downy. When fully grown the leaves are dark green and shiny above and paler green beneath. In autumn they turn a rusty yellow. The petioles are stout, long, with an enlarged base. Stipules are absent. The western and southwestern forms have smaller leaves, , than the eastern forms , an adaptation to the drier climates in the west. Flowers The flowers are small, across, with 4–5 narrow, greenish white petals. The pedicels are downy. The 4- or 5-part calyx is downy and imbricate in bud. The corolla has four or five petals which are white, downy, spreading, hypogynous, and imbricate in bud. The five stamens alternate with the petals. The pistillate flowers bear rudimentary anthers. The filaments are awl-shaped and more-or-less hairy. The anthers are ovate or cordate, two-celled, with cells opening longitudinally. The ovaries are superior, hairy, abortive in the staminate flowers, two to three-celled. The style is short, the stigma 2- or 3-lobed, with two ovules per cell. Fertile and sterile flowers are produced together in terminal, spreading, compound cymes—the sterile being usually fewer and falling after the anther cells mature. Flowers are produced in May and June. Some find the odor unpleasant but to others the plant has a delicious scent. Fruit