Ptelea trifoliata - Hoptree

Ptelea trifoliata, also known as the Hop Tree, is a little-known North American species that is not widely planted in European gardens, despite its remarkable adaptability. This shrub or small tree is not an elm, but a cousin of the lemon tree, just like Poncirus trifoliata and Mexican Orange, with which it shares a highly aromatic foliage. Its discreet spring flowering is both fragrant and melliferous, and is followed by clusters of winged fruits that resemble those of the elm and remain decorative until late in the season. Its beautiful, dark green, trifoliate foliage turns a brilliant golden yellow in autumn. While the Ptelea may not be spectacular, it is useful for difficult areas. This undemanding shrub also provides a good source of food for bees and small garden fauna.

Ptelea trifoliata, from the Rutaceae family, is native to a vast area covering the eastern part of North America, from Mexico to the United States and Quebec. In the wild, it is often found anchored in rocky hillsides in mountainous areas, on shallow soils where it develops thick roots.

The Hop Tree develops several thin and twisted trunks, displaying a generally open habit and a sparse, wide crown supported by upright and intertwined branches. It is a large, hardy shrub or small tree with slow growth, reaching a height of approximately 6 m (20ft) and a width of 4 m (13ft), depending on the growing conditions. The bark covering the trunk and branches is initially smooth and reddish-brown, becoming more grey and slightly grooved in appearance, and peeling over time. The branches bear a very dense, deciduous foliage that falls late in autumn and develops late in spring. When crushed, it gives off a musky and lemony aroma, which can be off-putting. The leaves, which are somewhat soft in texture and measure 6 to 15 cm (2 to 6in) long, are divided into 3 lobes with pointed tips. They are a fairly dark, glossy green on the upper side. The foliage turns golden yellow before falling.

Ptelea trifoliata offers a discreet flowering in April, with clusters of small, cream-white to pistachio-green star-shaped flowers, 1 to 2 cm (1in) wide, appearing among the leaves. They are intensely nectar-rich and exude a heady fragrance reminiscent of honeysuckle, more perceptible at dusk, which may or may not be appreciated by humans. The flowers are followed in late summer by generous clusters of small nuts, each surrounded by an oval, papery beige membrane, 2 to 2.5 cm (1in) in diameter. Dispersed by the wind, they are enjoyed by many birds and small mammals. These fruits, which are also aromatic, can be used as a substitute for hops in beer brewing.

The Hop Tree will find a special place in gardens that embrace nature. Far from extravagant blooms and lush foliage, it offers simple yet highly useful flowers and fruits, supporting life in the garden. It is valuable in difficult areas, on rocky soil and in somewhat shaded areas that are neglected by other shrubs. While it appreciates the sun and moist soil that provide it with more luxuriance, it is capable of withstanding summer drought once well established in slightly deep soil. It can be placed near the house if one enjoys its fragrance, in a natural hedge or a shrub border. For example, it can be associated with small maples (Acer campestre, monspessulanum, griseum), Poncirus trifoliata, honey tree (Tetradium danielii), Cotinus, and deciduous euonymus, all of which are equally easy to grow. Its very slow growth allows it to fit into smaller gardens.

The Hop Tree is also a medicinal plant used in the traditional medicine of the Native Americans.