Gondwana on our doorstep

For me, one of the joys of the Australian National Botanic Gardens (ANBG) is the rainforest gully. I first ‘got into’ plants many years ago when I lived in Tasmania and spent much time working in the cool temperate rainforests there. I became acquainted with such iconic trees as the Myrtle Beech (Nothofagus cunninghamii), Southern Sassafras (Atherosperma moschatum), Huon Pine (Lagarostrobos franklinii) and Leatherwood (Eucryphia lucida) which flourish in the lower reaches of the gully.

I’ve been fascinated with cool temperate rainforests ever since. They are like time capsules, ancient relics from the past when Australia was part of the supercontinent of Gondwana and these forests dominated the land. But when Australia broke free about 50 million years ago and became drier and more arid, they shrunk considerably, giving way to tougher competition such as the Eucalypt forests.

Unknown to most people, small pockets of cool temperate rainforest survive in southern NSW, in the sheltered valleys of the coastal escarpments at high altitude, where the rainfall is high and misty cloudy weather is frequent. However the dominant tree here is the Plumwood (Eucryphia moorei), a close relative of the Tassie Leatherwood, and named for the pink or plumy colour of its wood. It ranges from Bulli Pass near Wollongong to the Howe Range just over the border in Victoria.

The fossil records show that the Eucryphia genus was widespread in Gondwana. There are now only seven species in the world – two in Chile and five in Australia. A second species in Tasmania is a smaller montane version of the Leatherwood, once considered a variety. And in recent times two new species with very restricted distribution have been discovered – one in the cloud forests of the wet tropics in 1970, and the other in the subtropical forests of northern NSW/Southern Queensland in 1994.

Some of the largest and best examples of Plumwood forest can be found in Monga National Park, about 20km south-east of Braidwood. The trees here can reach enormous sizes and ages, with some ancient specimens reportedly measuring four metres in width and estimated to be two to three thousand years old.

Penance Grove is an easy and delightful spot to view the Plumwoods of Monga. Turn off the Kings Highway at River Forest Rd and follow the signs south. A raised 240m boardwalk with interpretive signs leads you through the wonders of this magical grove which evokes what the ancestral forests of 100 million years ago probably looked like.

Due to low light levels, the understorey is sparse and dotted with graceful tree ferns which provide a high platform for Plumwood seedlings to germinate out of reach of nibbling swamp wallabies.  As they grow, they extend their roots to the soil below before eventually encompassing the host plant. Sadly, a few of the tree ferns have been ‘beheaded’ by illegal plant collectors in recent years.

The Plumwood is an attractive tree due to its pinnate leaves (which are unique for this genus) and its large cream-coloured, strongly scented flowers. If you visit in early Autumn, you’ll see the petals sprinkling the rainforest floor like snowflakes.

The genus name Eucryphia was bestowed by Melbourne Botanic Gardens Director, Baron Ferdinand von Mueller in 1863, with the name derived from the Greek for ‘well hidden’, referring to the cap which is formed by the sepals. The specific name is in honour of botanist Charles Moore, Director of the Sydney Botanic Gardens from 1848 to1896.

Plumwood  trees can also be seen in the rainforest gully at the gardens. Next time you visit the ANBG, look out for five or six specimens on the Main Path on the southern side of the creek just to the west of the café.

Plumwood at gardens
Plumwood tree along the Main Path at the ANBG.
Penance Grove
Penance Grove walking track in Monga National Park
Pinnate leaves
The unique pinnate leaves of the Plumwood
Plumwood Flower ANBG M. Fagg
Plumwood flowers (Credit: ANBG)