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Home gardeners become accidental citizen scientists for Wollemi Pine

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by Andrea Wild, CSIRO

When the unusual branches of a tall tree were first noticed in a canyon northwest of Sydney in 1994, it sparked great excitement in the botanical world. The tree was new to science. It had very few living relatives and a lineage dating back millions of years to the Cretaceous period.

Scientifically named Wollemia nobilis, Wollemi Pine is a conifer in the same family as Kauri Pine and Norfolk Island Pine. It grows in small pockets within a 10 square kilometer area northwest of Sydney. It is listed as critically endangered, with fewer than 100 known adult trees existing in the wild.

Botanist Dr. Heidi Zimmer of the Australian National Herbarium said the tree has many unusual features that make it interesting to botanists. "The trees have multiple trunks and their bark looks quite distinctive, a little like chocolate bubbles," Heidi said.

"The branches grow rhythmically, with shorter leaves growing during winter and longer leaves during the warmer growing season. This results in a repeating pattern of different length leaves along each branch. "Trees are both male and female, having the male or female cones forming at the tips of the branches. "The tallest Wollemi Pine in the wild was 42 meters when we last measured it a few years ago."

For the first decade after it was recognized as new to science, Wollemi Pine was grown only in botanic gardens, sometimes in protective cages to prevent theft. The plants were mostly propagated from cuttings, not grown from seed.

In 2005, due to huge public interest in this rare tree and to protect wild populations from illegal collecting, Wollemi Pine was made available to home gardeners in Australia and many countries around the world. Little were they to know they would accidentally be taking part in a global experiment.

Wollemi Pines that have thrived in home gardens could hold the secrets to successful conservation plantings. Heidi and Cath Offord, from Botanic Gardens of Sydney, decided to survey home gardeners around the world to discover the best growing conditions. "We realized home gardeners could reveal the best soil, climate, rainfall and other conditions for Wollemi Pine, given it was growing across the world," Heidi said. "Conservationists could then use this information to select sites for planting Wollemi Pine to expand its current range in the wild or in botanic gardens globally.

"We released a survey with questions about location, soil type, fertilizer use, growth in pots versus planting in the ground, tree height and more. "More than 1,500 people from 31 countries responded. Some people shared how much their tree meant to them or that they used them as Christmas trees. 'Wolly' was a popular nickname."

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Monday, July 31, 2023