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Tristaniopsis laurina

Water Gum, Kannooka

Family: Myrtaceae

A very commonly planted tree, reaching 30 metres tall in its natural habitat. It has smooth brown-grey mottled bark.

It grows naturally along most of the entire coast of NSW, into the east of Victoria, and north into Queensland to around the Sunshine Coast. There are also a few record on the western slopes of NSW but these appear to be erroneous.

It is a common tree in rainforest and sclerophyll forest on freshwater creeklines in gullies, in sandstone and on other substrates, especially in places like the Royal National Park and elsewhere. It can be seen with its roots entirely in moving water. In some locations, it can completely dominate the bed of creeks and streams, creating a matrix of stems and branches in amongst sandstone boulders.

Tristaniopsis spp. have simple and alternate leaves, often heavily crowded on stems. In this species, the leaves somewhat resemble leaves of the exotic Oleander, oblanceolate, to about 12 cm long and 3 cm wide, dark green above and pale greyish white below, with scattered oil glands and a prominent midvein.

Tristaniopsis spp. have 5-merous flowers which are somewhat staminate; the interesting aspect is the stamens are fused into clusters or fascicles, opposite the petals. The 5 petals are often circular. Inflorescences are often axillary, with branches of 3 flowers (triads) or flowers in dichasia. In this species, the flowers are produced in groups (dichasia – in opposite pairs) of 7-15, in leaf axils and near the terminals; deep yellow in colour which is an attractive feature, about 1 cm wide with stamens not overly showy, but up to 20 produced in each of the 5 small ‘clusters’, in each flower.

The fruit is a capsule with a distinctive shape, about 10 mm long.

In the garden

A very hardy tree with an attractive canopy and overall form. It has been popular in parks and as a street tree for a long time.

Relatively easy to grow, although many Myrtaceae trees can take a while to establish and grow. But this is balanced by trees being very long-lived. This species can grow relatively quickly.

It will provide dense shade. Needs some room to grow as it will spread out. Expect a 20 m tree if grown in a garden over time, to about 10 m wide if not controlled.

It can be pruned heavily and turned into a dense topiary or hedging plant.

Likes a well-drained soil with some enrichment.

May be susceptible to Myrtle Rust.

The yellow flowers can be produced profusely, and the fruit are also ornamental.

Propagation

Propagation from seed or soft-wood cuttings.

Other information

Some cultivars are available. The most popular of these is marketed as “Luscious” which is registered as T. laurina ‘DOW 10’. This form is from the NSW north coast and has broader leaves, about 2 to 3 cm wide. It has been planted commonly since about 2013.

Another cultivar is called ‘Hot Tips’ with variegated leaves new bronze-red growth.

Can regenerate from seed bank after fire as well as branch shoots and suckering stems/trunks. Does not usually get burnt in fires as it grows almost purely on creeks.

Tristaniopsis is a genus oif about 40 species, distributed in Malesia to Burma and Thailand, Australia and New Caledonia. Australia has 3 species, all endemic. There are currently 2 species in NSW. 

Tristaniopsis – has its roots in the closely related genus Tristania which is named in honour of Jules Marie Claude de Tristan (1776-1861), a French botanist about whom not much information can be found online. Tristaniopsis means “resembling Tristania”; the two genera have similar leaves and flowers. However, Tristania neriifolia (the sole species) has opposite leaves whereas Tristaniopsis spp. have alternate.

laurina – having leaves resembling the genus Laurus – Bay Trees and other laurels (Family: Lauraceae)

This species is not considered to be at risk of extinction in the wild. 

NSW Flora Online (PlantNET) – Tristaniopsis laurina profile page       https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=tristaniopsis~laurina

Gardening with Angus – Tristaniopsis laurina profile page and ‘Hot Tips’ profile page https://www.gardeningwithangus.com.au/tristaniopsis-laurina-water-gum/
https://www.gardeningwithangus.com.au/tristaniopsis-laurina-hot-tips-water-gum/

Wrigley, J.W. & Fagg, M.I. (2001). Australian Native Plants – Propagation, cultivation and use in landscaping. 4th edition. New Holland Publishers, Pty. Ltd. Australia.

By Dan Clarke