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Saving rare orchids that are ‘confusingly difficult’ to grow in labs: Q&A with orchid expert Marc Freestone

Few plants capture the imagination quite like orchids. When orchid fever gripped England in the early 1800s, wealthy aristocrats sent out orchid hunters to forests around the world in search of these exotic flowering plants. Many died in the process. Even today, collectors seek out the rarest and the prettiest of orchids from the wild, and orchids are among the most widely traded plant groups in the world.

But many species of orchids are now under severe threat of extinction. Several are threatened by illegal collections from the wild because many orchid species occur in just a few locations, and removing them leads to the extinction of the species. Other orchids, especially the ones that grow in grasslands, are losing out to agriculture, grazing and development.

Leek orchids are a case in point. They’re a group of small, native wildflowers found in bushlands across southern Australia. Of the 140-odd leek orchids known today, one-third are at risk of extinction, primarily from habitat loss. Several species, such as the lilac leek orchid (Prasophyllum colemaniae), whose only known population was destroyed by the development of a railway line, are already extinct. Others, such as the Shelford leek orchid (P. fosteri), are down to a handful of plants.

Leek orchids occur in bushlands across southern Australia, and are threatened by habitat loss. Image by Marc Freestone.

Time is running out for the endangered leek orchids. In fact, for some of the more threatened species with just a few populations, captive breeding and reintroduction to the wild might be the only way to save them, researchers say.

But there’s a problem: leek orchids are deceptively hard to grow in labs, unlike many other orchids that can be easily artificially propagated. “Growing leek orchids is confusingly difficult,” Marc Freestone, a doctoral student at Australian National University, working with the Orchid Conservation Program at the Royal Botanic Gardens Victoria, told Mongabay.

Freestone and his colleagues are, however, hopeful that they will soon be able to crack the code.

Mongabay spoke with Freestone to find out more about leek orchids and what it takes to protect these tiny wildflowers.

Marc Freestone. Image courtesy of Marc Freestone.

Mongabay: What do you find most interesting about leek orchids?

​Marc Freestone: It’s not so much about their looks (I like to think I’m a bit more discerning than that — although some are certainly very pretty!). I think I’m drawn to leek orchids because so many of them are at risk of extinction. And because some species can look a bit drab, they can slip away without most people ever knowing they existed. To me, they seem delicate and utterly defenseless against humans who have engulfed their world. Ironically, some species are now totally dependent of humans for their survival. I feel a great sense of responsibility to help them.

How many species of leek orchids are at a risk of extinction, and what are the main causes of the species’ decline?

​Officially we have 39 species listed as threatened under Australia’s national environmental law, making leek orchids the fifth-largest genus of plants listed under that law. That’s about a third of the approximately 140 leek orchid species Australia-wide. Only a couple of species occur outside Australia in New Zealand.

Most of the threatened species grow in grasslands, woodlands or seasonal wetlands in the southeast of the country, areas with fertile soils and that were heavily cleared for agriculture in the first half of the last century. They cling on in narrow roadsides, beside rail lines or in rural cemeteries — tiny pockets of land that have never been plowed. For example, the lilac leek orchid (Prasophyllum colemaniae) grew beside a rail line in the eastern suburbs of Melbourne before works on the rail line destroyed the only known population in the ’70s. The only known population of the tan leek orchid (P. erythrocommum) north of Melbourne was destroyed when a firebreak was put through it during bushfires in 2009. Species that are on the very brink include the Shelford leek orchid (P. fosteri), which hasn’t been seen for a couple of years and the gaping leek orchid (P. correctum) which is probably down to fewer than 10 wild plants on a rail line east of Melbourne. Both species have a small amount of seed stored at the Royal Botanic Gardens Victoria, but that seed is getting older, it’s viability is probably decreasing, and we don’t know how to get it to grow with any measure of confidence.

In an earlier interview, you mentioned that despite efforts to manage these orchids, their populations are still declining. Could you tell us why?

​Most of our really rare leek orchids have active management plans, but for many of them their populations are still declining. We don’t know why, but it’s probably a combination of sustained below-average rainfall in the past few decades, combined with the inevitable loss of genetic diversity encountered by species with small populations. Other threats, particularly weeds and inappropriate fire regimes, are also significant for some species.

Green leek orchid, a vulnerable species. Image by Marc Freestone.

Do you see captive breeding as the only way of saving the endangered species of leek orchids?

For our most critical species that are known from few, small populations that are declining toward zero plants despite our attempts at managing them, there really doesn’t appear to be any other alternative to captive breeding. There are probably 10 to 20 species of leek orchids that fall into this category. Some other threatened leek orchids are not quite at that point yet, and for those, continued emphasis of land management practices is probably a better option for the time being.

Why haven’t researchers figured out how to grow these orchids in labs? And are you close to any breakthrough?

Growing leek orchids is confusingly difficult. The Royal Botanic Gardens Victoria grows many other endangered Australian orchids by extracting the symbiotic fungi that live in the orchid’s roots, growing the fungi on petri dishes, and sprinkling on the orchid seed. The fungi are required to inoculate the seed to get it to germinate. But for some reason, leek orchid seed rarely germinates using this method, or any other method. My research project is testing a bunch of theories, ranging from seed viability, growing conditions, and the identity of the fungi that we find in the roots of the leek orchids. We don’t have any breakthroughs yet, although the results of chemical testing show that seed viability doesn’t appear to be a major issue. At the moment we have several large germination trials underway and a large DNA identification study for the symbiotic fungi — so we’re optimistic that the answers will lie somewhere in there.

Could you tell us about the symbiotic fungi that leek orchids are associated with, and why they’re important?

All wild orchids harbor symbiotic fungi that live in their roots and the surrounding soil. Due to the microscopic size of orchid seed, all orchids rely on these symbiotic fungi to inoculate their seed when it lands on the soil, prompting it to germinate (orchid seeds don’t have enough food reserves in them to germinate by themselves). Most species of Australian orchids appear to have very specific relationships, often each orchid has its own unique species of symbiotic fungus. However, some preliminary data that we have suggests that leek orchids can associate with multiple species of fungi, which begs the question: Which species of fungus is involved in the seed germination process? To answer that, we are burying small packets of seed around the wild leek orchid plants, hopefully some will germinate and we can then identify the species of fungus in the newly germinated seedling and compare it to the fungi we find in the roots of the adult plant at different times of year. We will then know if using the wrong fungus is the cause of the poor germination results in our laboratory trials.

Seeds of leek orchids are incredibly hard to germinate and grow in the lab. Image by Marc Freestone.

How is the Threatened Species Recovery Hub and Royal Botanic Gardens Victoria involved in saving these orchids? What species are you working on currently?

The Australian government’s Threatened Species Recovery Hub is providing funding for this project, along with the Hermon Slade Foundation, Australian National University (who are funding my Ph.D.) and the Victoria state government. The research is based at the Orchid Conservation Program at the Royal Botanic Gardens Victoria. The Rural City of Wangaratta, Project Platypus and the Australasian Native Orchid Society are also providing field assistance with the project. It really is a team effort and the generosity of our project partners and funding agencies is heartening and inspiring.

We are working mostly on four main study species that are relatively common, but closely related to critically endangered species to which we will hopefully be able to apply our research findings. We are also collecting seed from our most threatened species, so that we will be ready to go if we can make a breakthrough on how to grow them.

What do you think would happen if Australia lost its leek orchids?

The alpine parts of the southeast of the country are still relatively untouched and there are several species of leek orchid that are very common up there. To be up in those high plains in summer when the alpine leek orchid (P. tadgellianum) is in full flower, the air sweet with the scent of its nectar, its flowers crawling with insects, you can really get a feel for what the lowland grasslands would have been like once upon a time, when species like the gaping leek orchid would have numbered in the millions, its flowers playing an important role in the food chain. Now there are perhaps 10 plants left. If it goes extinct, Australia will have lost part of what makes it unique. A small part perhaps, but when added to all the other threatened species in this country, a significant part.

Is there anything else that you would like to add?

I don’t think I have anything left to add other than to say — fingers crossed — stay tuned over the next year or two for any breakthroughs!

Coastal leek orchid is known from a few hundred plants near Portland, Victoria. Image by Marc Freestone.