When I was working as a naturalist on a Great Lakes cruise ship, we often visited the sand dunes on Lake Michigan near Saugatuck. While the passengers were racing around on dune buggies, I walked about admiring the local flora and fauna. One small tree which caught my eye was the Hop Tree (Ptelea trifoliatum).
Hop Trees thrive on forested and open dunes along Lake Michigan.
While leading walks in Sunnybrook Park along the West Don River, I have occasionally noticed a tree with 3 leaflets on a central stock which bear a surprising resemblance to Poison Ivy Leaves.
This is the Hop Tree. Trees in Canada (John Laird Farrar, p. 230) describes the tree as Rare in Canada; occurs in southwestern Ontario on the north shore of Lake Erie. No indication of it growing near Toronto. Michigan Flora (Voss and Reznicek, p. 863) mentions that it will grow along rivers and the edges of floodplain forests. This is a perfect description of Sunnybrook Park near the Don River.
The leaflets are nearly stalkless and the margins are nearly smooth. There is a strong citrus odor when the leaves are bruised.
Here is a view of the leaf underside.
The lateral buds are very small and sunken.
The flowers are small and greenish-white.
The fruits are flat and one or two seeded.
The bark is reddish-brown and smooth when young.
It becomes rough with age.
Hop Trees grow up to about 8 meters in height and 15 centimeters in diameter.