Extra TERRESTRIAL assistance

A team of scientists and volunteers is nurturing endangered native orchids to help them regain ground control in their natural habitat, writes MILLIE ROSS

As gardeners and plant lovers, it can be hard to resist taking a precious plant home to try to grow it, even if we know it will fail. But the truth is, some plants cannot be cultivated in our gardens, and nor should they be. They are so intimately connected with their natural environment, to the soil, climate and species that are in their location, that they cannot survive without them.

Native ground-dwelling terrestrial orchids are such plants. Unlike the more familiar and showy epiphytic species, terrestrial orchids are tiny. Complex, unique, and beautiful, they are best observed on hands and knees, crawling through their natural habitat. And right now, orchids are blooming.

Australia is recognised for orchid diversity, with some 1700 species found across the continent, but we also lead in their decline. One-sixth of all plant species that are listed as endangered in the Environmental Protection and Biodiversity Act are orchids. Habitat destruction, added competition from introduced weeds, and grazing by rabbits and stock have devastated populations. Species that were once so widespread that early colonisers described their flowers as snow on the landscape have since been reduced to a handful of plants or have disappeared altogether.

saving species

An innovative project at The Orchid Conservation Centre, at the Royal Botanic Gardens Victoria's Cranbourne site, is trying to bring back some of the most endangered orchid species. Led by botanist Dr Noushka Reiter, who works with research scientists, partner organisations and volunteers, the program has grown and reintroduced some 20 orchid species from New South Wales, Victoria and South Australia.

Noushka says the key to their success has been to understand all the pieces of the ecological puzzle. “In the past, we have looked at endangered species in isolation, but increasingly we look at the whole ecology,” she says. “We must get that right – understand all the parts of the puzzle, the pollinators and what is happening in the soil.

That is when we have success.”

“With such limited numbers of plants, genetic diversity can be an issue”

The terrestrial orchids are highly specialised, having evolved relationships with very particular pollinators – in some cases a single matched insect species. They lure their pollinator with offers of nectar, pollen or even sex, releasing pheromones to attract their mate. Then, if the orchid successfully attracts its pollinator match and produces seed, it requires another specialised partner, mycorrhizal fungi. Attaching itself to the seed, the fungi acts as a root system, absorbing the water and nutrients that are needed for the orchid to grow.

These extraordinary evolutionary collaborations allow these orchids to survive in some of the most inhospitable growing environments, from coastal heathlands and bogs to the driest eucalypt forest. If any of these related species are absent, reintroduction is impossible.

meticulous process

The Orchid Conservation Centre consists of two shadehouses, a potting shed and a makeshift laboratory in a portable building. “We had to crowdfund to pay for the lab, and we continue to look for support,” says Noushka. Here the team works to isolate the individual fungal partners for each threatened orchid, and piles of petri dishes illustrate the needle-in-a-haystack nature of the task. Once the fungi are identified and the seed successfully germinates, the seedlings are flasked into nutrients, and grown on until they are large enough for potting, then grown on again. Pots are mulched with she-oak (Allocasuarina spp.) leaves to encourage the fungi.

The day I visit, a dozen pots of crimson spider orchids (Caladenia concolor) are in flower. They were once widespread in central Victoria, “but there is so little of their box–ironbark forest habitat left that now we have only two small populations of a handful of plants,” Noushka says.

They are carefully hand-pollinated to ensure seed production. The team has only recently identified the pollinator – a wasp that is attracted to the flower by its smell, which is a bit like citrus. "The scent itself is unusual, as wasps are ordinarily attracted to a burnt or unpleasant scent."

Noushka takes flowering potted orchids into the field to lure, observe and identify potential pollinators. Often the pollinator no longer exists, and this informs where they might try to reintroduce a population. “There is no point putting plants back into a place where they have no chance of reproducing naturally,” she explains.

With such limited numbers of plants in the wild, genetic diversity can be an issue. The brilliant sun orchid (Thelymitra mackibbinii) survives in only two wild populations, of about 15 and 20 plants respectively. Noushka grew seedlings from each, but they both exhibited weak growth. “Finally, we managed to get the two populations flowering simultaneously and crossed them, and immediately we saw that the offspring produced were far superior plants.”

Over the past few years, Noushka and her team have introduced literally thousands of orchids back into the wild, partnering with volunteers to plant them in national parks or on protected private land. “I travel thousands of kilometres through the season, following the plants as they flower,” she says.

While her work focuses on supporting wild plant populations, as they succeed in establishing orchids in the wild, some may end up in our gardens. “The metallic sun orchid (Thelymitra epipactoides) used to be very common in Victoria, New South Wales and South Australia. It has a stem of blazing flowers. They were listed as vulnerable and are now endangered.

They should be weeds!” We can only hope they become common again and that Noushka and her team get the required support for their work.