Australian Plants for Bonsai

April Daly

Desirable qualities of bonsai include: a strong, prominent root system, a thick trunk, heavy lower branches, and small leaves, flowers, and fruit. Leaf size can be reduced through bonsai culture; flowers and fruit cannot. Therefore, it's a good idea to start with a plant that has smaller flowers in the first place, and scale the tree's size to match.

Traditional bonsai are grown outdoors, but in the last 20 years, many enthusiasts have begun to grow tropical and subtropical species in their homes. These indoor bonsai are much easier to maintain. Like any other houseplant, they do not require special soil or daily watering, and their beauty can be enjoyed year-round.

Where to Start

Collecting plants growing naturally is often the best way to begin a bonsai. Wind, fire, drought, lightning, and plain hard luck can dwarf and contort trees into amazing shapes. Obviously collection from National or Conservation Parks and Nature Reserves is not acceptable but sometimes a suitable plant can be located on private land. If you find such a tree, think hard about what kind of bonsai it would make. If you wish to collect it, get permission from the landowner, grab your shovel, and think hard again. Be sure you are committed to caring for your tree as a friend; don't dig up a novelty whose charm will pass. Whenever you collect, always refill any holes you dig to prevent soil erosion, and offer to plant a new tree in place of the old.

Whether bought or collected, a new tree in your home is a mystery that you should take the time to study. Before starting to prune and shape your tree, live with it a while and get to know its character. Imagine what it will look like pruned into different shapes, or how it might appear in the future. The two of you will be living together for a long time.

Australian Species for Bonsai

Most of these plants are subtropicals, which means that they need a cool, dry rest in winter. The fastest way to kill these plants indoors is overwatering during this period. Always use a pot with a drainage hole! Use your fingers to check the top 25 mm (1 inch) of soil. If it's still moist, don't water. On the other hand, all of these species use a lot of water in hot weather, so check the pot every day in summer. The best way to water in summer is to put the whole pot in a bucket of water up to the lip of the pot for about fifteen minutes or until the top of the soil appears damp. Then just let it drain and leave it be until the top 25 mm (1inch) of soil has dried out. In winter, water over the surface of the soil, then let it dry down about 50 mm (2 inches) before watering again. All plants benefit from additional humidity in the home during the central heating season. If you don't already have a humidifier, consider purchasing an inexpensive cool mist unit. Humidity is good for you, too.

Acacia

Acacias are trees and shrubs mostly grown for their small yellow flowers, which grow profusely in fluffy little pom-poms. As bonsai they must be pruned back severely in early spring as they are prolific growers. All acacias need as much light as can be provided, and should be turned often to maintain even growth. In summer, they enjoy going out to the patio for fresh air, and can be left out until night temperatures start to fall below 13 degrees C (55 degrees F). They like a lot of water and fertilizer when in active growth. They require cool conditions (not less than 10 C; 50 F) and less water in winter, although they should never be allowed to dry completely. If they decide to drop their leaves in winter, simply keep them barely moist until new growth appears in spring.

The best for bonsai are Acacia paradoxa (Kangaroo Thorn - previously known as A.armata), A.dealbata (the Mimosa sold by florists in the USA) and A.podalyriifolia (Queensland silver wattle, which will tolerate higher winter temperatures).

Brachychiton

These odd little trees are grown more as curiosities than formal bonsai subjects, but they are excellent for the beginner. They don't need a lot of water and will thrive on "benign neglect". Brachychitons can be kept in any position, although they prefer a sunny window. Brachychiton rupestris (Queensland Bottle Tree) is the best for bonsai, and will grow in any temperature range from 4 to 24 C (40 to 75 F), but should be protected from sudden cold drafts. It is called "Bottle Tree" because of its large, bulbous trunk and roots that it forms in order to conserve water. B.populneus (Kurrajong) is faster growing and will tolerate temperatures down to -4 C (25 F). The cooler they are, the less water they need.

• Plant your tree in a one-gallon thin plastic pot (available at any nursery).
• Allow the tree to grow in a sunny window without pruning the branches.
• When the trunk reaches 50 mm (2 inches) or so in width, slice 25 mm (1 inch) off the top of your pot and remove the same amount of soil.
• Continue this procedure once a month until you have exposed 100-150 mm (4-6 inches) of strong taproots.
• Using pruning shears, cut the trunk back to the lowest three branches.
• In spring, remove the plant from the pot and slice horizontally through the root ball, cutting away about half of the tree's roots.
• Repot into a bonsai pot and keep warm and barely moist for one month while the new roots form. Cut back branches at any time to create a bushy appearance. The results will be
• impressive.

Callistemon

These are evergreen shrubs or small trees which produce really amazing red, purplish, or yellow flowers. The flowers are actually long spikes of tiny flowers with very long stamens, giving these plants the nickname "bottlebrush". If you can provide cool conditions in winter (not under 10 C; 50 F) and a sunny position in summer, these plants will be easy to grow. They are quite vigorous, and require heavy pruning after flowering. Water and fertilize heavily in summer, but keep on the dry side during winter. Although they do need sun, they will survive the winter under fluorescent light if conditions are cool, so try placing them in a basement near a window under a standard shop light. Move them outside in spring.

Eucalypts

Evergreen trees and shrubs with beautiful bluish-green leaves. These plants will thrive in any soil, under any conditions, as long as they have sun. They are extremely durable and adaptable in the home, and will tolerate light shade and winter warmth better than most other Australian plants. They are an excellent choice for the beginner. Since they are rapid growers, the only difference between a good job of pruning and a bad one will be about two weeks. Stand them outside in full sun for the summer to get the best, most compact growth. Water thoroughly from spring to autumn, sparingly in winter. Keep them potbound or they will take over the house. The best are Eucalyptus globulus (Tasmanian blue gum) with striking blue leaves and rapid growth, E.gunni (Cedar gum) which is slower growing, and Corymbia citriodora (Lemon scented gum - previously Eucalyptus citriodora).

Grevillea

Grevilleas are evergreen shrubs and trees, mostly grown for their showy foliage, although some have beautiful flowers. The foliage is fern-like, and can really give your collection an exotic appearance. Grevillea robusta (Silky Oak) is the most commonly grown, because it can tolerate light shade and some winter warmth. These trees require additional humidity to keep their foliage attractive in winter. Use a humidifier, and do not place them near a heat source. These are a rapid growers, which can go from seed to ceiling in about five years. Don't be afraid to cut them back at any time. For those who wish to grow a large tree, minimize your pruning and you may be rewarded with a show of white flowers in spring. The best Grevillea for bonsai is G.rosmarinifolia, which has tiny, needle-like leaves and adorable red (occasionally pink or white) flowers carried in handsome yellow bracts. This plant must have a cool winter to bloom successfully. Highly recommended.

Melaleuca

These evergreen trees and shrubs are absolute knockouts as bonsai. They are pest-free, tolerant of light shade and winter warmth, easy to propagate by seed or cutting, and just plain good natured. Young branches have beautiful black bark, aging to white. The trunks show off with papery, exfoliating bark that becomes more marked with age.

Further Information

April Daly is a 30 year old resident of Chicago, Illinios. She is a former business consultant, now happily unemployed and a keen exponent of bonsai culture. Currently she is maintaining about 70 plants. This article is based on growing experiences in the northern hemisphere but Australian growers should find the advice invaluable for developing bonsai downunder.

Australian Plants online - June 1997
The Society for Growing Australian Plants