Common name: Australian gardenia

Australian gardenia is a small flowering tree reaching heights of up to 7 m (23 ft) in its native habitat, though it is more typically 3 to 5 m (10 to 16 ft) tall with a slender trunk supporting a densely leafy rounded crown. 

The leaves are oval, large to medium-sized, dark glossy green on top and with a smooth or prominently ribbed surface, depending on the variety or subspecies. They remain on the tree in all seasons.

Flowers are white, star-shaped with five petals, sweetly fragrant, and female and male flowers on separate trees. They bloom in showy clusters, mostly in spring and on and off the rest of the year. They are followed on female trees by globular fruit, up to 10 cm (4 in) in diameter, green when young, becoming dull yellow when ripe, usually from late summer to autumn.

There are two known subspecies with distinct climate adaptations, subsp. fitzalanii, which is adapted to dry, coastal strips and lowland areas, and subsp. tenuipes which is adapted to hilly, high-rainfall areas.

Use

The plant's small size, lush green foliage and fragrant flowers make it a suitable small ornamental tree or hedge plant for the home garden or for growing in a large container. A bonus is that it attracts butterflies, which are drawn in by the nectar-rich flowers. It is widely planted in its native range as a street or landscape tree. However, its cultivation is discouraged because of the tendency for birds to eat the fruit and disperse the seed, which germinate readily.

The fruit is sometimes eaten fresh in its native range and is reported to have a fair flavour and texture but is considered a minor fruit.

Climate

Depending on the subspecies, it grows in moderately humid to very humid subtropical and tropical coastal to mid-elevation climates, generally areas with annual lows of 16 to 24°C, annual highs of 25 to 33°C, annual rainfall of 1000 to 4000 mm and a dry season of 6 months or less.

Growing

New plants are easily started from seed, but good practice is to grow new plants from cuttings taken only from male trees, as they flower but do not produce fruit, removing the risk of the seed being dispersed and becoming a weed problem.

Performs well on free-draining loam and sand soils of a moderately acid to neutral nature, generally with a pH of 5.0 to 7.0, and on sites with partial sun to light shade exposure.

Problem features

Birds are attracted to the fruit on female trees and disperse the seed outside of cultivation, making it a potential weed risk in non-native areas. It is assessed as a high weed risk species for Hawaii by the Hawaii Pacific Weed Risk Assessment (HPWRA) project.

Books

• Oakman, H. 1981, Tropical and subtropical gardening, 2nd ed., Jacaranda Wiley Publications, Milton, Queensland

• Oakman, H. 1995, Harry Oakman's what flowers when : the complete guide to flowering times in tropical and subtropical gardens, University of Queensland Press, St. Lucia, Queensland