I have made some interesting observations over the years regarding the Brachychiton endemic to the Ormeau area, Brachychiton sp. Ormeau (LH Bird AQ435851). It is listed as critically endangered under the federal Environment Protection and Biodiversity Conservation Act (1999) and endangered under the Queensland Nature Conservation Act (1992).
Fairly typical to many of the Brachychiton species, it will go through an array of morphological changes before it reaches mature foliage, which is simple; however, juvenile foliage is deeply lobed with long fingers. Flowers are greenish white and pods are brown and 30-60 mm long. Pods generally contain one to five bright yellow seeds, but I have observed up to 11. The seeds are covered in a hairy exotesta, the hairs are easily dislodged and cause some irritation.
Of the limited population of mature specimens of this species that remain, only a few bear any quantity of seed, and even then, since the beginnings of my observations about 18 years ago, I have seen two fruiting episodes! It is interesting to note that the seed viability is so close
to 100% and produces no noteworthy deformities, suggesting that fertile specimens are not yet at a point of genetic limitation.
Limitations on seed production and natural recruitment in seeding events are noticeable even before ripening. It can be seen that the pods are absolutely plagued by exotic rats. There is barely a pod remains on the tree that isn’t subjected to some chewing. A good proportion of what is left is attacked by a grub, which eats the seeds before moving onto the next pod.
Even after intense insect and rat attacks, 2012 was such a good year that these minor setbacks did not affect the amount of seeds that were produced. On a number of visits to the seeding trees, I had noticed that one tree in particular had been subjected to highly unethical seed collection methods and quantities. It was very disappointing. Natural limitations are often beyond human control, but regulations put in place on collection to protect already dwindling species must be upheld to allow for optimal self-recovery of these species within their environments.
After a reproductive dormancy of 12 years (prior to the recent seeding event), a huge crop of seeds was produced just before the torrential rains that south east Queensland experienced in the summer of 2013. Based on many other seed germination preferences, I considered large quantities of rain just prior to, and into seed maturity, to be favourable. On closer investigation and trials, I found this to be quite the opposite. Of the seeds that I collected and propagated through December and January 2012/2013, I found that large amounts of rain prior to germination resulted in very poor germination percentages. Even with precautionary fungicide applications to all of my seedling trays, germination was less than 10%, compared with more than 90% in the exact same conditions minus the rain. All of my trials were conducted outdoors in the full weather (in a rat proof situation).
This implies habitat and climatic limitations and intolerances for the species. A bumper year of seed production was followed by what would appear to be extremely unfavourable recruitment conditions. Records for the area indicate that 2001 (the last time the trees produced a large quantity of seeds) was a wet season also.
Interestingly, the seeding specimens all occur on Regional Ecosystem 12.3.1 (gallery rainforest on alluvial plains) classified as endangered under the Vegetation Management Act (2009). It is estimated that less than 10% of this ecosystem’s pre-clearing extent remains. Taking that into account for an already limited habitat area, these areas are frequently subjected to temporary inundation, thus subjecting seeds and seedlings to what has been observed to be unfavourable growing conditions. Regardless of the fact that this ecosystem is highly susceptible to weed invasion and was cleared extensively for agriculture, it would appear that the conditions of recent times have resulted in severe limitations on the species reproductive success. Areas subjected to grazing would see seedlings trampled and young plants eaten. Brachychitons are frequently eaten by cattle with the Queensland Bottle Tree (Brachychiton rupestris) used as fodder during droughts.
Brachychiton sp. Ormeau is a handsome, hardy tree with a limited population. Juvenile foliage is interesting and unique, and the new growth is beautiful and bright maroon-red. Flowers are not spectacular by Brachychiton standards, but are beautiful in their own right. It is a tree that can be easily propagated and is certainly worthy of cultivation. I am proudly donating my seedlings to the conservation of the species.
Article and photos by David Madden, Land for Wildlife member, Guanaba, Gold Coast