Red Leaves

Skyrail Nature Diary: November 2011


We are just coming out of our winter so it’s getting hotter as we come into what we could call our spring.

Some trees are still covered in red leaves whilst others have become deciduous after their leaves turned red such as the Damsons.

Other trees are completely red without any leaves on them at all like our Flame Trees which are flowering bright red at foothills of the cableway. For some trees, leaves turn red all year around like our Quandongs or Bleeding Heart. Strangely enough, other plants like Davidson Plum, Rusty Laurel, certain Lily Pilies and even Eucalypts have reddish or pinkish leaves which are actually new and far away from falling off, even if some of them are drooping as if they ready to wilt.

In a temperate climate with four seasons the trees usually turn red and lose their leaves at the same time in autumn and not spring. The reddish new growth seems to be a tropical phenomenon which might be quite new for some of our guests visiting from other regions.

So what’s it all about with the red coloured leaves? Why are some young and old leaves red whilst others are green in between? There are a lot of theories out there. Some argue it is a protection against insect attacks however if this was the case, you would expect to find the same thing occurring in a temperate climate. Another theory is that it might actually have to do with our tropical sun in that the red colour could be some sort of sunscreen for young leaves by reflecting away the intense tropical red light that could otherwise disrupt the processes in the leaves.

Cauliflory

Another phenomenon that might be quite new for our guests from higher latitudes is called cauliflory. Quite a lot of tropical plants have the habit to produce their flowers and subsequently fruits on the trunks and oldest branches rather than close to the branch tips. Some quite striking examples at the moment are our Bumpy Satinash on the lookout at Red Peak, our Native Daphne at Barron Falls and the Black Bean flowering just about everywhere. So what could be the reason for that? Most likely it has to do with fruit size or pollination and seed dispersal. Whilst plants that flower and fruit on their thin branches can’t carry heavy fruits like Jackfruits, Cocoa or even our Black Bean, one main advantage of this habit is that it increases the number of possible pollinators and seed dispersers.

How wonderful must it be for the flightless Cassowary to pluck some fresh fruit from a trunk and buttress well in it’s reach in place of the half rotten windfall that it usually has to deal with. As a reward for the tree the cassowary will carry the seeds of these fruits several kilometers through the forest and deposit them in a nice ‘starter package’ of manure.

Written by Michael Gailer, Ranger, Skyrail