Discovery

Davies’ Waxflower (Phebalium daviesii) is slender shrub endemic to Tasmania’s north east coast. Known from only three collections made around the St. Helens area back in late 1800’s, it was believed to be extinct. But in 1990 a population of 55 plants was rediscovered on the Georges River by fern expert Michael Garrret. Recognised and listed as critically endangered in the wild, in 1995 a joint party of RTBG and DPIPWE staff visited the population to collect cutting material. The cuttings were passed on to the RTBG Nursery where 26 individuals from the original population were successfully established. (DPIPWE), also HERE, and listings page HERE

Safeguard

To conserve the genetic diversity of the Phebalium collection the nursery maintains duplicate clones of each individual. This ensures that the diversity we hold is secure. This has meant a process of re-propagating all of the individuals every 2-3 years to ensure plants do not become too old and maintain a healthy collection. Maintaining this collection requires careful curation by the nursery staff. “Many of the individuals are relatively easy to propagate from cuttings” says Lorraine Perrins, Horticulturist at the RTBG Gardens Nursery, “But a few of the plants prove problematic, so I need to take large numbers of cuttings from these plants to make sure I get adequate results.”

Sadly since collecting took place, erosion from flooding and storm damage has reduced the wild population to less than 20 individuals. However over time the collection in the nursery has grown to 40 individuals as the plants began self seeding around the nursery. Knowing the plants were setting good seed attempts were made to collect it, but these largely met with failure. “Getting a seed collection would further safeguard the diversity we’re holding, but we initially had problems” comments Lorraine. “It’s not really obvious when the fruit are ripe, we also didn’t realise how small the seeds are or how explosive the dispersal mechanism is. It’s meant that the conventional method of catching fallen seed in trays below the plants was just ineffective”.

Summer Harvest

So in Spring of 2008 nursery staff decided a more thorough approach was required. Nursery Supervisor Michelle Lang constructed purpose built hessian bags to enclose completely 45 of the larger plants held in the nursery (representing 32 individuals). After flowering was completed the bags were fitted around the plants with the hope of capturing any seed that might develop. In the middle of January 2009 the bags were carefully removed from the plants and the contents (a mixture of old leaves, flowers and fruit debris) poured into trays. The material was then passed over to Tasmanian Seed Conservation Centre coordinator James Wood for cleaning.

James says “Lorraine and I had a sneak peak at one of the bagged plants back in the middle of December to see what was going on. We recovered 95 seeds which was very encouraging as the previous years total collection was only 85 seeds. With 45 plants bagged up we were confident that we’d have a collection of at least 4 to 5 thousand seeds.”

Phebalium harvest (iii)
James Wood and Margo White carefully harvest the last of the Phebalium seed at the RTBG Nursery.
What was finally recovered from the harvested debris actually turned out to be well over 34 and a half thousand seeds. “That’s a seriously big collection” says James “We were all pretty stunned, to be honest.” The collection quality also turned out to be good too. After cleaning, a cut test assessment revealed the collection to be around 94% full. The collection has now been divided in half and one half sent off to the UK, to be housed at the Millennium Seed Bank (home of the Royal Botanic Gardens, Kew landmark Millennium Seed Bank Project). “That’s a back up collection” explains James “we’re not keeping all our eggs in one basket. Kew will look after our seeds until we need them back. It’s a standard safeguard for all our collections.”

The Next Challenge

Phebalium daviesii seed (iii)
Seeds of Phebalium daviesii. A small sample of huge harvest. The next step is to get them to germinate.

Back in Hobart the seed has been safely stored away and for James the real work begins. “Now we have the Phebalium banked I’ll have to determine how to germinate it and that will not be easy.” he says. In fact studies have shown that Phebalium like a lot of other Australian Rutaceae are actually extremely difficult to germinate. “The cut test shows the seed we collected is good. We know that they can germinate as we’ve had a few seedlings turn up under benches in the nursery. The sobering thing for me is that the nursery plants have more than likely been dispersing tens of thousands of seed each year, but we’re only seeing one or two seedlings pop up every few years.” James will need to do a lot better than that. “I need to be able to get over 75% germination on a test sample before I can say my initial work on this collection is complete. That’s going to be tough.”

Fortunately a seed collection of this size allows the opportunity for research work to be carried out. “Wild plant species are often difficult to germinate” says James “Typically they can require a quite specific series of conditions to trigger germination.” For seed banks with a small collection only a small percentage of seeds can be used in germination trials. “A big collection gives us the chance to run a really wide range of tests and gives us a greater opportunity to identify and confirm the important triggers. I expect to get into testing this spring. It’ll be interesting, but I’m ready for a long hard slog to get this to pass” he says.

The germination trials  aren’t just an academic endeavour. By understanding the germination requirements seed can be turned into plants and new individuals can be returned to the population. If germination is understood then seed longevity research can also be conducted. By understanding these two traits conservationists can make better evaluation as to the health of the population. As James explains “By understanding how long seeds can last and how they germinate we may be able to better manage sites to encourage seedling recruitment. That information is important for conservation workers in the field.”