Acacia Bonsai Care

Acacia dealbata can be kept in full sun or partial shade. The plant tends to close its leaves when it has received enough sunlight, so it can remain in partial shade and is suitable for indoor bonsai cultivation.

A good growing temperature is 68–82°F (20–28°C). A tree planted in the ground may tolerate temperatures as low as 23°F (-5°C) briefly, but a container-grown bonsai should be moved into a protected shed or indoors during cold weather.

A suitable winter range is 41–52°F (5–11°C). When grown indoors, keep it near a west-, south- or east-facing window and maintain good air circulation.

Acacia can be propagated from seeds or semi-hardwood cuttings taken in summer.

Before sowing, subject seeds to thermal shock. Place them in boiling water for 10 minutes, allow the swollen seeds to cool, and then sow them in the growing medium.

When using stem cuttings, rooting hormone and bottom heat can promote rooting.

Acacia has moderate water requirements. Keep the growing medium moist, but do not leave it soaked for long periods.

Reduce watering during winter unless the tree is kept in a warm environment. Occasional misting can be beneficial, although it is not essential.

Acacia branches take shape relatively quickly and younger branches are flexible and easy to wire. Take care around thorns, which may be pruned if necessary.

Wire after flowering while the tree is actively growing, or when the tree has been completely defoliated in late spring. Older branches are quite brittle and require extra care.

Avoid damaging the attractive flaky bark. Guy wires are useful; copper wire may also be used if the branches are protected with raffia. Marks become less noticeable as the bark ages.

Acacias grow quickly and require regular pruning. Their growth tends to concentrate toward the top, which can cause lower branches to die back.

If the tree flowers, carry out the main pruning after flowering, usually at the end of winter or the beginning of spring. Main branches may be pruned throughout the year.

Leave a generous stub when pruning and preserve any bud that should develop into a branch. Remove the stub after it has dried, and apply cut paste to reduce infection and dieback. Leaf pruning is generally unnecessary because acacias have compound leaves.

Repot an acacia bonsai every two to four years: approximately every two years for younger trees and every four years for mature specimens.

If pruning the roots, keep the tree relatively cool and make only a light root prune. The root system is not especially strong, and the nitrogen-fixing nodules should not be removed.

Choose a relatively deep bonsai pot and use a basic free-draining bonsai soil mix. Acacia can grow in acidic or alkaline soil.

During the growing season, feed every three to four weeks with a general-purpose fertilizer that has a fairly low nitrogen content. Excess nitrogen encourages long internodes.

Feeding can be paused in winter when the plant is kept at a cool temperature of 41–52°F (5–11°C).

Acacia bonsai trees are usually pest-free, but poorly maintained plants may be attacked by red spider mites, scale insects and aphids.

Appropriate systemic treatment can be used when needed. Good light and air circulation also help prevent these problems.

Overwatering may cause Acacia dealbata to “bleed” sap from the trunk. This is known as gummosis: a natural way for the plant to release excess pressure and protect the trunk and stems. Wipe the sap away before it marks the bark.

Leaf shedding can indicate insufficient watering. Water the plant when this symptom appears.

Defoliation can encourage the formation of fine twigs and smaller leaves.