The Hoptree (Ptelea trifoliata, Rutaceae) is a deciduous shrub or small tree 6-8 m tall with a broad crown. It is native to North America, from southern Ontario, Canada southeast to Florida, USA, west to southern California and south to Oaxaca in southern Mexico.
While most often treated as a single species with several varieties, some botanists treat the Hoptree as a group of four or more closely related species:
- Eastern Hoptree P. trifoliata var. trifoliata (P. trifoliata, sensu stricto)
- Florida Hoptree P. trifoliata var. baldwinii (P. baldwinii)
- Western Hoptree P. trifoliata var. crenulata (P. crenulata)
- Narrowleaf Hoptree P. trifoliata var. angustifolia (P. angustifolia, P. lutescens)
Ptelea, of Greek derivation, is the classical name of the elm tree, which was transferred by Linnaeus to this genus, because of the resemblance of its fruit to that of the elm. Trifoliata refers to the three-parted compound leaf.
A small tree but often a shrub of a few spreading stems. It makes part of the undergrowth of the Mississippi river valley, and is found most frequently on rocky slopes. Has thick fleshy roots, flourishes in rich, rather moist soil. Its juices are acrid and bitter and the bark possesses tonic properties.
The twigs are slender to moderately stout, brown with deep U-shaped leaf scars, and with short, light brown, fuzzy buds. The leaves are alternate, 5-18 cm long, palmately compound with three (rarely five) leaflets, each leaflet 1-10 cm long, sparsely serrated or entire, shiny dark green above, paler below. The western and southwestern forms have smaller leaves (5-11 cm) than the eastern forms (10-18 cm), an adaptation to the drier climates there.
The flowers are small, 1-2 cm across, with 4-5 narrow, greenish white petals, produced in terminal, branched clusters in spring: some find the odor unpleasant but to others trifoliata has a delicious scent. The fruit is a round wafer-like papery samara, 2-2.5 cm across, light brown, maturing in summer. Seed vessel has a thin wing and is held on tree until high winds during early winter.
The bark is reddish brown to gray brown, short horizontal lenticels, warty corky ridges, becoming slightly scaly, unpleasant odor and bitter taste. It has several Native American uses as a herbal medicine for different ailments.
- Bark: Dark reddish brown, smooth. Branchlets dark reddish brown, shining, covered with small excrescences. Bitter and ill-scented.
- Wood: Yellow brown; heavy, hard, close-grained, satiny. Sp. gr., 0.8319; weight of cu. ft., 51.84 lbs.
- Winter buds: Small, depressed, round, pale, covered with silvery hairs.
- Leaves: Alternate, compound, three-parted, dotted with oil glands. Leaflets sessile, ovate or oblong, three to five inches long, by two to three broad, pointed at base, entire or serrate, gradially pointed at apex. Feather-veined, midrib and primary veins prominent. They come out of the bud conduplicate, very downy, when full grown are dark green, shining above, paler green beneath. In autumn they turn a rusty yellow. Petioles stout, two and a half to three inches long, base enlarged. Stipules wanting.
- Flowers: May, June. Polygamo-monoecious, greenish white. Fertile and sterile flowers produced together in terminal, spreading, compound cymes; the sterile being usually fewer, and falling after the anther cells mature. Pedicels downy.
- Calyx: Four or five-parted, downy, imbricate in the bud.
- Corolla: Petals four or five, white, downy, spreading, hypogynous, imbricate in bud.
- Stamens: Five, alternate with the petals, hypogynous, the psitillate flowers with rudimentary anters; filaments awl-shaped, more or less hairy; anthers ovate or cordate, two-celled, cells opening longitudinally.
- Pistils: Ovary superior, hairy, abortive in the staminate flowers, two to three-celled; style short; stigma two to three-lobed; ovules two in each cell.
- Fruit: Samara, orbicular, surrounded by a broad, many-veined reticulate membranous ring, two-seeded. Ripens in October and hangs in clusters until midwinter.