Acer carpinifolium aka Hornbeam Maple

Acer carpinifolium, or hornbeam maple, belongs to the Sapindaceae family. It comes from central and southern Japan. Its range includes Honshu, Kyushu, and Shikoku. This deciduous plant forms a small tree or large shrub. Garden trees reach 20–30 feet (6.1–9.1 metres), with similar spread. UConn gives a smaller garden range of 20–25 feet (6.1–7.6 metres). RHS lists heights up to 39 feet (12 metres). Several trunks often support its dense crown. The crown starts vase-shaped and becomes oval or round.

The bark stays smooth and grey. Its leaves look like hornbeam leaves rather than most maple leaves. They lack lobes and grow in opposite pairs. This paired layout helps tell the tree apart from hornbeams. Each leaf has an oval shape and a pointed tip. Strong, parallel veins run from the midrib to toothed edges. Young leaves may show bronze tones and fine hairs. The hairs fade as the green leaves mature. Fall brings gold, bronze, yellow, or brown shades. Some leaves stay on the tree into winter.

Small flowers appear in short racemes, chiefly during May. Their green to yellow-green colour makes them easy to overlook. Male and female flowers grow on separate trees. The fruit consists of samaras with spreading wings. The leaves and autumn colour provide more garden interest than flowers. This tree suits a lawn, patio area, or woodland edge. It also works as a specimen or screen. Gardeners may find it hard to buy.

Grow it in fertile soil that drains well but stays moist. It accepts full sun and partial shade. UConn reports stronger growth where trees receive full sun. RHS lists neutral soil and clay, loam, sand, or chalk. Water needs and routine upkeep are modest. Published USDA ratings range from zones 4–7 to 5–7. RHS gives it an H6 rating. Restrict pruning to late autumn through midwinter.

Serious pest and disease trouble is not usual. Aphids, scale, borers, caterpillars, and mites can occur. Diseases include wilt, leaf spots, canker, root rot, and honey fungus. Leaf scorch can also affect it. PFAF lists no known hazards or medicinal uses. Its sap provides a drink or syrup after boiling. It has less sugar than sugar maple sap. PFAF also records using leaves to help preserve stored produce.