This small, usually shrub-like tree bears its flowers on spikes — a feature reflected in one of its French names, érable à épis, which literally means “maple with spikes.” Typically found in moist understories and on rocky slopes, the mountain maple is the smallest of Canada’s native maple species.
Mountain maple grows 3 to 10 m tall. Its short trunk is crooked and twisted. Its bark is thin, dull, reddish to greyish-brown, smooth or slightly grooved.
Its slender twigs are yellowish-green to reddish-brown or pink. The young twigs are coated with grey hairs, giving them a velvety look.
Like all maples, the palmately lobed leaves grow in opposite pairs along the branches. Slightly longer than they are wide, each leaf has three to five pointed lobes with numerous coarse, irregular teeth. The upper surface is yellowish-green, while the underside is paler and pubescent, covered with fine white hairs.
Come autumn, the leaves of this tree take on shades of red and orange, recalling the colours seen in red maple (Acer rubrum) and sugar maple (Acer saccharum).
The greenish-yellow flowers are arranged in clusters at the tip of the stems.
The fruit is a pair of winged keys that meet at about 90°. Each key is 1 to 2 cm long and the keys are arranged in erect clusters. In fall, the fruit is often bright red, later turning yellow or pinkish-brown.