Identifying characteristics:
The common hop tree is a slow-growing, low, spreading shrub or small tree
to 25 feet with a slender trunk up to 8 inches in diameter. Because it is
in the citrus family, the bark, leaves and fruit of this tree are pungent
and aromatic. The shiny leaves are
alternate and pinnately compound with three essentially unstalked leaflets,
the middle one usually larger. The leaves are gland-dotted (seen with strong
backlighting using a hand lens) and dark green, becoming yellow-green in
the fall. The small, greenish-white, fragrant flowers
are produced in June in clusters at the ends of the branchlets, each cluster
sometimes containing both bisexual and unisexual flowers. The fruit is a round, flattened, two-seeded samara
produced in drooping clusters that may persist on the tree into December
or later. The common name refers to the fact that the fruits were once used
in beer-making as a substitute for hops as they contain a bitter principle.
The buds are tiny, rounded, woolly, pale-yellow and are hidden within
the bases of the leaf stalks. Terminal buds are absent. The young bark
is reddish-brown with numerous conspicuous lenticels, and the mature bark
is dark gray, rough and scaly.
Similar species:
Ecology:
The common hop tree is hardy to zones 3 to 9 and has a widely-scattered
distribution from Ontario and New York to Florida and west to Minnesota.
It is native to south-east and extreme east-central Iowa, growing along
wooded streams, rocky bluffs, low-lying sandy places and along the edges
of woods. This species is very adaptable, but grows best in well-drained
soils in sun or shade. This species is susceptible to attack by treehoppers
which secrete a residue of honeydew, turning the twigs black. Leaf spot,
rust and root rot and scale can be problematic.
Uses:
The wood is hard, heavy and yellowish-brown, with a satiny texture,
but unimportant commercially because of the tree's small size. The common
hop tree is of limited value to wildlife: thickets provide nesting places
for birds and bees are attracted to the flowers. Hop tree juice was once
used as a substitute for quinine to treat many ailments, and the bark was
used for medicinal purposes. The low, spreading habit of this tree makes
it ideal for use as a hedge plant and it is an interesting native plant
for ornamental use in the eastern US. The cultivar 'Aurea' has attractive
yellow new growth that fades to a lime green and 'Glauca' has striking blue-green
leaves, both produce effective shrub borders.
