(Un)Forgotten forbs

Bredbo gentian

Snuggled into the drainage lines of sphagnum moss, the Bredbo gentian (Gentiana bredboensis) is at home in boggy conditions, but as the Saving our Species team found out, it also loves the sunshine.

Only one known population of this critically endangered species is located within a 20 m x 20 m patch in Ngarigo Country, east of Bredbo, just outside the south border of the Australian Capital Territory. Before 2019, the population had dwindled from 200 to fewer than 12 individual plants.

Half of the remaining patch was then affected by the Black Summer bushfires of 2019–20, but with the vegetation around it burnt and the La Nina rains that followed, the tiny forb bounced back in surprising numbers, with almost 280 plants counted.

This allowed the Saving our Species team to collect seeds and conduct further study into this fascinating species, which had been notoriously impossible to germinate from existing seed collections. We collected 7,000 seeds and sent them to PlantBank for storage and research into discovering what makes these plants tick. A sample of this fresh seed was tested to see if there was a chance it could survive and germinate, and for the first time, germination in the lab was highly successful.

Since 2021, the emergence of new plants has slowed to fewer than 10 individuals each year, so this study and seed collection has proven to be a precious opportunity and has opened the possibility to grow this forb outside of its only known location. Our researchers are working to learn and understand more about the Bredbo gentian and help species numbers thrive more and more into the future.

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Mountain trachymene (Trachymene scapigera)

The endangered mountain trachymene (Trachymene scapigera) is a real Goldilocks of the forb world.

There are 3 known populations of this species – one in Kanangra-Boyd National Park and 2 in Gurnang State Forest on Gundungurra/Wiradjuri country in the Central Tablelands of New South Wales.

Almost all plants in the 3 known populations grow within 10 metres from the edge of a creek – they won't grow in the creek as it's too wet, but they won't grow too far from the creek, as it's too dry. They like a bit of shade from eucalyptus trees, but not too much shade...the conditions have to be just right.

Occasionally, an intrepid individual will grow further from the creek, but if the weather is hot and dry, the adventure stops there - so the number of plants declined across all 3 sites by 55% during the drought before the 2019–20 bushfires. The species then took further blows as the Kanangra–Boyd population burnt in December 2019 and then flooded the following month. The biggest population in Gurnang was overshadowed by introduced blackberry plants, which took over the site due to the La Nina rains.

Despite these impacts, the species was able to rely on some clever survival skills. The mountain trachymene can survive at the rootstock, meaning the plants can resprout from their roots or grow rhizomes (horizontal underground stems) and form new child plants. This has helped the species slowly begin to recover and populations have returned to be within 10% of their pre-drought numbers. While this is great news for Saving our Species researchers, it can also cause a bit of a headache. Parent and child plants can start growing into each other, making counting individual plants difficult to undertake. So, the team has been trialling various survey techniques as part of their ongoing monitoring of the species populations.

Monitoring the populations will help researchers keep track of the mountain trachymene's recovery across the 3 sites and inform how best to manage the species into the future. The team has also begun weed control at the Gurnang site to ensure the blackberry plants don't overshadow these fussy little forbs to make it just right so they can start to thrive once more.

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Elusive cress

Just as its name suggests, the endangered elusive cress (Irenepharsus magicus) is, well, elusive. While the species has been well-recorded over the border in north-eastern Victoria, it has been some time since this species has been spotted in New South Wales, with just one population recorded near the Geehi Dam in Kosciuszko National Park.

The elusive cress is a member of the Brassicaceae, or mustard, family. Like other mustard family members, this species sits dormant until it rapidly takes advantage of perfect conditions by emerging in the thousands – kind of like Sydneysiders at Bondi Beach on a hot day.

While we know this happens, what constitutes perfect conditions for the elusive cress has yet to be discovered. Ecologists suspect that part of the reason for this forb's elusiveness may be that it only germinates and flowers following disturbance, which could be anything from soil movement to bushfire. With this in mind, the Saving our Species team is planning future surveys around the Geehi dam to boost their search efforts should the area experience fire or other disturbance.

Another possibility behind the difficulty in recording this mysterious species is that, like many native plants in the mustard family, the elusive cress could be mistaken for one of its weedy Brassicaceae relatives, such as the wild radish (Raphanus raphanistrum), which is found in agricultural areas and on roadsides – meaning the elusive cress could easily be overlooked by the untrained eye.

There is still much more to learn about this elusive cress, especially as it continues to elude records, so it's more important than ever that Saving our Species continues investigating the species. Understanding more about its reproductive ecology and its habitat will support the team to ensure the survival of this intriguing forb.

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