eucalypts drop branches when you don't expect it

When we were in Darebin Parklands the other day, we met some people at the big pool in the bend of the creek and stood discussing the recent floods.

Crack! A branch dropped straight down from one of the trees around the edge of the pool. No warning except that infamous sound.

A young boy and his pup had been standing there only moments before.



Of course, inquisitive Penny (and her humans) went over to have closer look. Probably not too intelligent, but we were working on the theory that lightning doesn't strike twice in the same spot.



It seems that it's not known why some trees (not just eucalypts) unexpectedly drop limbs.I haven't found any information on the internet about the actual process of dropping the limb but here is an interesting article. I took a couple of closeups of the end of the branch, and I don't know if it looks as if there is any particular disease at that spot.





And a shot of the place it dropped from, high up the trunk.



As we wandered further through the park, we came across an even bigger branch that had dropped previously.

a dog visits Darebin Parklands in the heat

In the cool hours after dawn Penny and I headed for Darebin Parklands to see how the plants and animals have made it through the current heat wave.



One of the first sights was a eucalypt that had dropped one of its branches.

Eucalypts are one of the most common trees in the Parklands and I wondered whether there will be more dropping of limbs if this heat continues, so I had a look around the Internet. I found it surprisingly difficult to locate information from Australia, but I suppose that reflects two realities - the dominance of the English-speaking net by the US and the number of eucalypts growing in the US.

Page 5 of the Danville Weekly of 2006 had an article about 'sudden limb drop syndrome.' They'd been having a twelve-day heat wave - temperatures above 100 degrees for nearly two consecutive weeks. Sounds even worse than here. (I think it must be the Danville in California.)

About why limbs drop suddenly, the writer said:

Researchers are still learning about the syndrome, but they theorize that during periods of hot dry weather, trees suck more water into their branches. This causes the branches, which are already arid and brittle, to snap from the weight of the water...One woman reported hearing a loud crack and then seeing water spill out of a large branch.

That last sentence sounded rather strange, but I'll reserve judgment.

I've heard eucalypt branches snap and drop many times, in the bush - the thump of the timber hitting the ground is frightening but I've never been close enough to be alarmed.

I found a fascinating snippet in an article by Robert L Santos of California State University:

Drought in recent years has made Californians more conscience [sic] of water conservation especially in regard to plant life. Some eucalyptus species have proven to be drought resistant. In the 1917 [sic], there was a drought in California where temperatures hovered between 110 and 120 degrees F. It was found that the foliage on most eucalyptus trees burned with the amount of tree damage being dependent upon type of soil and wind. Trees in loamy soil did better than those on sandy soil because it contained more moisture. A survey was done concerning the number of trees killed by the 1917 drought. It was found that of 2,885 blue gum trees examined only 9 died. The red gum did even better in that only 10 trees died out of 4,461.

I'd say that's true of the Parklands. I think many of the dead trees are wattles.



Two hopeful points, then - the eucalypts are tough; and the wattles are good at reproducing. Penny had a good look at the babies around the dead tree and gave them the paws-up for survival potential.


















Anyway, back to our walk...
Many areas of grass were dusty and dead, with lines of cracks stitched across the ground.



We spent some pleasant time chasing balls but we took care to avoid the areas with the potentially leg-breaking cracks. (One of us chased balls; the other is too old and too tired out from the heat to raise a gallop, so she, having the advantage of arms and fingers, threw the balls.)
Then it was time for a cool off in the creek.






Here is another article with information on 'sudden limb drop':Summer Limb Drop on Ornamental Trees by Pam Geisel, farm advisor at the University of California.