Camden white gum (Eucalyptus benthamii) is a vulnerable species that only exists in a few places near Sydney.
Along the Nepean River near Camden, southwest of Sydney, the tall, white trunks of these majestic trees were once common. They were an important part of the river's ecological community. But clearing for agriculture and urban development has left the survivors growing too far apart to pollinate each other. This means they don’t set high quality seed. No seed means no next generation.
A seed orchard for Camden white gum
How do you bring 40-metre tall plants together to pollinate? Scale the heights in summer to hand-pollinate their white flowers? Carry insect pollinators from tree to tree? Train birds to fly between them?
Our solution was to create a clonal seed orchard. We are growing exact genetic copies of the trees in the wild, side by side, in miniature.
Locating the wild trees was a major undertaking. Local citizen scientists assisted us and also helped collect DNA samples that guide the work. Using equipment such as pole cutters and ropes, we took small cuttings of each tree. At our labs at Black Mountain in Canberra, we grafted the cuttings onto robust rootstocks.
Nigel England, a forestry technician at the Australian Tree Seed Centre[Link will open in a new window], has been working on this technically demanding project for more than a decade. The orchard is now a cluster of trees standing several metres tall, in large black plastic-fibre tree bags. So far Nigel has “captured” more than 40 clones, each genetically identical to an endangered tree growing wild along the Nepean River.
“Now that I’ve got a decent population assembled, the clones have begun to flower, pollinate each other and set seed. So far, we’ve raised over 500 seedlings from this seed and they have all returned home to Camden,” Nigel said.
Camden Council[Link will open in a new window] has planted 500 seedlings in the Camden area. In the future, these seedlings will mature, pollinate each other and, importantly, nearby wild trees. These will set seed for a new generation of wild trees that retains the genetic diversity of the original Camden population.
After growing in tubes for around six months, seedlings are ready for planting.
Commercialising a conservation species
Many Australian hardwoods[Link will open in a new window] are prized overseas for pulp fibre, construction materials and as fuel for heating, cooking and industrial processes. Our Australian Tree Seed Centre supplies seed, including Camden white gum, to forestry plantations around the world. This seed comes from a seed orchard based on a population of Camden white gum at Kedumba Valley, near Sydney.
David Bush[Link will open in a new window] leads our Botanical Collections Group and knows the conservation value of commercialising a species.
"Camden white gum is a sub-tropical tree that is also frost tolerant. This means it is suitable for plantations in some regions of Brazil, Uruguay and the USA that have generally warm weather but can get sudden cold spells," David said.
"This species is estimated to be the tenth most widely planted eucalypt in the world. It's still vulnerable in its natural setting, but the plantations overseas provide a backup genetic resource, in addition to the steps we are taking to preserve it in its natural range," he said.
This project is part of the Greening our City Grant program proudly funded by the NSW Government.