Jacaranda peeling bark mystery

Eric Frei

Visual observation (over last 2 years in Brisbane) of bark lifting off in large pieces on some (not all) jacaranda trees. Beneath is a new lighter coloured cambium which eventually develops to the same appearance as regular Jacaranda bark.

The phenomenon peaked from Spring 2009 to Autumn 2010. Brisbane's annual rainfall average is 1150mm with the bulk of it's rain falling between October and April. From 2005 to December 2007 Brisbane was in a drought situation where rainfall was approximately half of it's annual average, however that still equated to over 500mm of rainfall per year. From about December 2007 the rain started to fall with some record falls in 2008 and 2009. The Wivenhoe dam level rose from a low of 16% in 2007 to 99% in early 2010 .... indeed the drought broke.

Some of the common attributes to the trees affected are (in my observation) trees that have limited root space. Trees that are grown in carparks, courtyards, surrounded by bitumen are more so affected than trees in open parks.

The bark that lifts is lower on the tree and seldom above 4m in height.

The bark that lifts appears to be around higher growth/stress points, similar to where growth striations occur.

The new cambium beneath has a uniformed appearance with only the occasional swirl or wound wood style of arrangement, it often has small cracks and fissures which resemble the typical exterior bark of a jacaranda tree.

I have not found any fungal hyphae, fruiting bodies or evidence of infection, pests, no sap weeping etc.

Could it be that jacaranda trees that were under greater stress during the drought period have grown so rapidly that they shed great plates of bark in one hit, literally pushing off the old exterior with a new layer beneath? Or is this a response to a pathogen?

A series of pictures follows, I did take increment cores from trees and compared them to a core from a sound non affected tree. There was no difference to the eye, all seems in relative order.





Restricted locations





Aged appearance later.



Core of affected tree





Core of non affected tree

Attached Thumbnails

           

     

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Garry Brockley

Ive come across two, instances of this in the last week, i wondered what was causing it, both are in confined areas, the sluffing of the bark isn't as extreme as the pictures youve posted, they were both in the lower forks under 3 meters where there are stress points.
your explanation makes alot of sense actually they have been stressed for a few years and now have grown with the large amount of water and nutrients available.
Thanks ekka for clearing that up i wont consider the tree stressed or in decline next time i see it, but it does look damaged when you first see it, if i get any take downs with this present i will take lots of pics, then we can have a good look at the evidence.

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glennak

Yes that seems be the cause but it doesn't look good. When I was contracting for the council and we had similar weather we had heaps of resident complaints about split trees and they were expansion cracks in Spotted Gums mainly. A local lopper cut one down as he decided it was dangerous (at least they have to get permits now)

Brent Ferris

I'm not familiar with the tree species, but all your pics Ekka show the trees growing in very confined spaces - possibly a water source problem, but also a high heat reflectance from the bricks behind.

I know you said rain has fallen in recent years, but trees often take time to exhibit a problem, and a similar length of time to recover. The excess bark may have developed as a response to drought, and the shedding as a response to more water being available.

Eric Frei

A lot of those trees will have to come out soon, some are pretty sick and some have failed.

Pretty insane planting putting jacarandas in such a spot, but that's landscapers and builders for you.

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Brent Ferris

Yep - builders and landscapers put completely inappropriate trees in dumb places here too! I guess it can be a common failing.