Black bean tree

How to identify a black bean tree

Black bean has a dense, rounded crown of glossy, dark green compound leaves, each with 9 to 17 oblong leaflets. Crushed leaves smell like freshly mown grass. In spring, short sprays of pea-shaped flowers 3 to 4 cm long grow straight from the older branches; they open yellow, age to orange and red, and are often half hidden by the leaves. Fat, cylindrical pods up to 20 cm long follow, then split to show a few large brown seeds. The bark is grey to brown and fairly smooth. Big pods lying on the ground under the tree are the easiest clue.

Growing a black bean tree in Brisbane

Black bean is a true local. The specimen used to name the species was collected at Moreton Bay in 1828, and it grows wild in rainforest along creeks and rivers. Brisbane's warm climate suits it, and it does best in deep, moist, fertile soil that drains well, in full sun or part shade. Garden trees usually reach about 10 metres, sometimes 20, with a crown 4 to 8 metres wide. That makes it a tree for large yards, acreage and parks rather than small suburban blocks.

What to watch out for

The roots spread widely. The Australian National Botanic Gardens and Gardening Australia both advise keeping this tree at least 10 metres from drains, sewers, house foundations, garages and pools, and Unitywater lists it among trees not to plant near pipes. The seeds are poisonous if eaten, causing vomiting and diarrhoea, so keep fallen seeds away from children. The leaves and seeds are also toxic to livestock. Pods drop in large numbers and litter the ground, and sawdust from the timber can irritate skin and noses.

• Poisonous parts. The seeds are poisonous if eaten and can cause vomiting, diarrhoea, stomach pain and dizziness; the leaves and seeds are also toxic to livestock.
• Mess. Big crops of pods drop and litter the ground under the tree.
• Irritant sap or hairs. Sawdust from cutting the timber can cause skin rashes and nasal irritation.
• Size. Garden trees reach 8 to 20 metres with a dense crown up to 8 metres wide, and wild trees can reach 40 metres.

Pruning and care

Young trees are slow to establish, so water them through dry spells and give them a liquid fertiliser while they settle in. Avoid keeping the soil soggy, because overwatering can cause root rot. Scale insects and psyllids occasionally turn up. When pruning, remove only dead, damaged or low branches, cut just outside the branch collar, and take off no more than you need. Large limbs over a roof or driveway are a job for a qualified arborist with the right gear.

• Tree pruning
• Tree removal
• Stump grinding
• Tree health assessment