Hedera rhombea aka Japanese Ivy

Hedera rhombea, or Japanese ivy, is an evergreen climbing vine. It belongs to the Araliaceae family and comes from eastern Asia. Its native range includes Japan and Korea. It grows on rocky slopes and climbs trees in mountain forests. Aerial rootlets help it grip trees, cliffs, and walls. Without support, its stems creep across the ground.

Garden size estimates differ between sources. RHS gives heights of 5–8 feet [1.5–2.5 metres]. Its spread reaches about 1.6–3.3 feet [0.5–1 metre]. NC State lists heights of 10–30 feet [3–9.1 metres]. RHS gives five to ten years to reach full size. Growth is fast, and the leaves stay green year-round. The dark, glossy leaves have clear grey veins. They grow in an alternate pattern along the stems.

Leaf shape changes as the plant matures. Young leaves have a diamond outline and three lobes. Their bases often have a heart shape. Adult leaves are mostly oval, with rounded or wedge-shaped bases. Leaves measure about 0.08–0.25 feet [0.025–0.076 metres] long. Young stems climb or trail across the soil. Mature stems stop climbing and can bear flowers. Small yellow-green flowers form upright umbels in autumn. Only adult branches with some sun produce these nectar-rich blooms. They draw pollinators, then give way to round berries. The fruit turns black from winter into spring.

Grow this ivy in moist soil that drains well. It suits shade, dappled light, or partial sun. RHS also lists full sun as suitable. It tolerates clay, chalk, loam, and sand across a broad pH range. Rich soil with plenty of humus gives the best growth. RHS favours alkaline soil and a sheltered site. Keep indoor plants moist, but avoid soggy potting mix. The species has an RHS hardiness rating of H5. NC State lists USDA zones 8a through 9b. It can cover banks, soften walls, or form a screen. Containers and indoor growing offer other uses, including in colder areas.

Pests include spider mites, mealybugs, scale insects, aphids, and vine weevils. Leaf spots can occur, including those caused by bacteria. Honey fungus is another possible problem, though RHS calls it rare. The plant is harmful when eaten by people or pets. Handling it can also cause skin irritation or an allergic reaction. Wear gloves and protective clothing when working with it. NC State identifies hederin as a poisonous compound in the plant. Its reported medical uses do not make the leaves or fruit safe to eat.