The following is what Colin Spencer of the City of Bunbury observed. Some active followers of the blogonforesthealth may have noticed his call in the comments section. In response to his observations, and in addition to her earlier blog posting, Katinka Ruthrof responds and … comes up with a suggestion. Food for thought?
Colin Spencer: Hello fellow tuart watchers
I have been closely observing Tuart trees in and around Bunbury. Most of them are producing prolific amounts of flower bud. There is an amazing litter of operculums under some trees.
I was expecting a spectacular mass of flowers, much like that seen in marris, jarrahs, red flowering gums etc. However, I was quite disappointed as it seems that when the bud cap drop, a very short amount of time elapses before the cream coloured stamens are either blown away by rain, or wind or just shrivel up and disappear. Some bud caps clasp the stamens so tightly that they also pull them off.
This very short flowering time, and perhaps even absence of actual flowers, stamens etc. makes me think whether there is much pollination of the flowers occuring. It seems that many of the tuarts around Bunbury have lost their bud caps and there hasn’t really been a flowering event? It will be interesting to see if the flowers have actually been pollinated and produce seed.
I understand that the flower buds might be predated by the tuart bud weevil. So I have been looking for the small holes drilled in the side of the bud cap, and also the offending weevil but haven’t seen any evidence of them.
???? like your comments
Katinka Ruthrof: Dear Colin,
Its great to hear that flowering is occurring in Bunbury too. A few weeks ago I received an email from an observer near to Lake Clifton who reported mass flowering in that site as well. I find it also interesting to hear about the short flowering period and flower loss. It could be due to a number of factors that can impact the bud between now and fruit development. For example, the buds can be predated upon (weevils, as mentioned), the flowers can be rain or hail damaged (did Bunbury receive a lot of rain during the storm?), pollinators could be lacking, or parrots can clip them off. If they survive all of that, they might become fruit! It’s an amazing process. So, the number of bud caps seen may be much higher than the number of flowers and hence the number of fruit.
We could do some phenology studies (studies of how plants and animal life changes over the seasons) to follow a number of buds through their cycle. I share your amazement Colin and it will be interesting to see what happens next. What do you think, would this be an interesting school project? Low hanging branches with buds are easy to study for children. Is the mass flowering a sign of the last gasp of a species to cope with a impending death, or, and I like this thought better: is it a sign of healthy trees responding to good weather conditions? Or is it much more complex than that? Next summer will tell us more about the significance of the mass flowering… Other observations are welcome!
Recording observations of flowering and seeding over many years in tuart would provide valuable insight into the reproductive cycle.
Heavy losses of reproductive parts are not uncommon in eucalypts, but substantial seed crops can still be produced despite the massive losses that can occur through the various stages that lead to capsule development. This may also be the case for tuart.
I have studied seed production over four years in the jarrah forest. Although each year was different, there were massive losses of reproductive parts through the developmental stages. On average there were 3.7 million flowers set per hectare each year; but a staggering 55% of the flower buds fell before they had a chance to flower. This left only 45% of the flower buds to complete their development. High levels of bud abortion have also been observed in karri (75%) and eastern states eucalypts (E. sieberi, 44%; E. globoidea, 67%; E. regnans, 50%). For jarrah, the combined losses through all of the development stages meant that only 7% of buds that were initiated actually completed development to set seed. The losses of reproductive parts through the early stages of the seed cycle were highly variable between years, and the size of the final seed crop could only be estimated late in the cycle once the capsules had begun to form.
In spite of these heavy losses of flower buds and other reproductive parts, the production of jarrah seed was still substantial; 429,000 seeds per hectare per year. So the tuarts may still be able to produce a reasonable seed crop.