Do Gums just drop branches? Sudden Limb Failure

TrevMcRev

I have my opinions on this, but am interested to see others responses.

Ekka mentioning the stigma attached to gums in another thread prompted the idea.

So what do you think about the general publics perception of the hazards of gum trees "just dropping branches" or what some might also call Sudden Limb Drop, or whatever else you think might be behind the fear many have of these trees.

Also, do those outside of Australia that have our eucalypts as exotics, think of them as dangerous trees, to be feared, should only be in parks, not suitable for home gardens etc...

I'm looking for both what you see as the publics opinion to be, as well as what you as an arborists opinion is.

Eric Frei

Some species are more prone than others.

Also, as part of the growth cycle shedding lower limbs is common.

Some of the SA court articles showed with the Red River Gums that SLD was repetative for certain trees, chances were if no previous sign of it then it wouldn't happen. Flaw in theory is every tree which had SLD history never did till the first one.

General public perception is not near the house and dont camp under one!

Often, and I mean a lot, people ring and want assurity as to how safe their gum tree is. You get there and there's a 100' gum over the house, nothing really wrong with it, how safe is it?

No matter how safe it is you can make it safer by some intelligent pruning and soil care ... avoid fertilizing as I believe growth on a euc is your enemy. Yeah, I'm way out there with this, just good soil conditions and mulch. Take our eucs to good soil places and wetter like UK or Cali and see what happens, they grow even bigger!

Eucs are open canopied, at times (like right now here) their branches can be over abundant with dense leaves and flowers ... even dropping and hanging, very heavy. That is on the end of natural lions tailed branches.

Bit of wind, bit of dry, bit of shade etc and you get a limb on the roof/car etc.

So, each tree within it's own right will have it's own issues depending on it's environment, but overall, people dont like them near houses.

Personally, neither do I when they are big. The one I recently pruned I'm happy with, it could get 50% larger and I'd still be happy, but if a new estate was built and they saved some 100' grey gum next to my house or a euc Grandis ... no friggin way!

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Jamie Myers

we get something similar with beech and oak (fagus and quercus) summer limb drop they look fine and then drop a massive limb without warning

Lee Winger

loads of tree over here drop limbs, horse chestnut, oaks, beech its very common here, it is also known as summer branch drop here.

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Lee Winger

I must read previous posts before I post lol

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dguntertrees

I also was going to mention summer branch drop in Beech in the UK. seems to me that no tree "just drops branches", there is ALWAYS a reason, it just may not be immediately apparent. Try explaining that to a client with a half metre diameter red gum branch on their roof/car/dog..However, I'm with Ekka on this one, good soil health and mulch help because they reduce the amount of CHANGE in the soil. I.e. keep water/nutrient levels more constant. BTW I've never seen a euc in any kind of trouble in the UK, but then there aren't that many of them. I'd say that they would struggle in fighting off fungal attacks...

groundpounder

Cottonwood and silver maple are the problem trees here. Maples begin the decay process early in their lives mostly due to hail damage. Target cankers on top of the limbs can make for hazards that can not be seen from the ground. Have seen limbs fall out just from the weight of rain on the foilage. In the '70s and '80s the suburbs grew out from the city in leaps and bounds. We live on the high plains, so there were no trees to provide shade for the new homes. How do you get some quick shade? You plant cottonwoods of course, preferably two or three feet from the house. Fast forward to 2007 and they are all beginning to decline. Dead cottonwoods everywhere. A boon for the low bidder. Most worrisome are the ones that are still hanging in there. Codoms and multi stems seem to be the rule rather than the exception, and there is root crown decay caused by thirty years of the irrigation system squirting the base of the tree. Add to that our frequent early or late snow storms while the leaves are on the trees (which I suspect has something to do with why there are no native shade trees here) and the possibility for large branch drop goes way up. A woman was killed a year or two ago while shoveling snow under a cottonwood. If you have a cottonwood or a very old silver maple on your property, this arborist rarely brings good news.

Eric Frei

Perhaps they do.

Man dies after tree branch fall - ABC News (Australian Broadcasting Corporation)

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Drouin Tree Service

They do for sure,the older they are more chance they "shed"a limb,or 2 or 3

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Urban Treecare NZ

I also have come across 2 large branch failures on 2 seperate oak trees this summer. Both have occurred on large scaffold branches that have extended to the outer canopy. Both failures have occured on the compression side of the branch or the upper side where strength occurs in Angiosperms in the form of 'ropes'. Both have failed at a point where a small amount of decay has been present due to an old pruning wound or historic failure.

Here a few pictures of one of the failures I cleaned up just after Christmas. This branch failured just after Christmas Day after getting a small amount of rain. It has been suggested that saturation due to rain may assist in failures of this kind....

I have also cleaned up a failure this year which resulted from a split in the neutral friction zone possibly due to resin pressure of summer. Here in Nz we have a second growth season from jan to feb in some Exotic species...

Attached Thumbnails

       

Q.Q.

I get that out here all the time, it's just drops limbs answer.
So we decided that it does just happen every now and again, so what advice do you give guy's?.
A proper prune and mulch the area, and always be mindfull?
Most of the time here it's the dead limbs that fall, not real big in size but they are sick of the mess and cleaning it up all the time.

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Q,Q's Tree & Garden Maintenance

FAMILARITY BREEDS CONTEMPT

Tilia

isn't there something called sudden branch drop- shigo and mattheck both with there individual theries, something about hot still days and and the compression and tension focusing on one spot with a bunch of evaperation passing through, usually explodes off in a way, a couple feet from the collar leaving a really jagged consistent brake. i don't know where i learnt that from,so don't take my word for but have seen what looks like the aftermath and clients have described the right story to fit the theories.

kazisgardening

I am interested in this topic as well. I have two ghost gums in my backyard and during recent high temperatures we had a large live branch drop for no apparent reason. It was very weird.

My bigger issue is the appropriateness of these trees in suburbia. My block in total is 850sqm, in my front yard alone I still have 5 ghost gums (there were ten). We removed 5 when we extended the house as the branches were in the building area and the other one was badly diseased.

Our remaining 5 concern me! They are very thin, spindly tall things whose branches all intertwine. I've got no idea how tall they are but they tower over the power lines and over our two story house. Our neighbours all have similar trees and the in the last 10 years, collectively, storm damage has smashed 2 cars, 3 fences, our electricity, and one loungeroom! Plus of course many large branches have fallen and not caused major damage.

Apart from the one that has recently died (for no apparent reason), the other four seem stable. But history has taught me that these gums will lose large branches from a great height every time we get a bad storm. The potential for damage is ever present. I obviously want these trees gone.

Just in case anyone thinks I am a tree hater I want to make it clear that I would replace them immediately with something more appropriate. I personally love Sydney Blue Gums but I fear it might be a bit big. Although my neighbour has a gigantic gum tree (unknown species) - it is large, lush and absolutley magnificant and I have never known it to lose one branch no matter how bad the weather. I think my safest alternative is to plant some bottle brushes, unless I can get some other advice.

I'm curious as to what the opinion of an abourist is of ghostgums being in sububia. Also any advice as to suitable alternatives. I want at least one tree and it must be native and suitable for local birds.

Eric Frei

We need to get a positive ID on the gum first, common names aren't as accurate as we'd like them to be.

Also if you can load up some pictures that would be great.

Do the trees have Protection Orders on them?

There's two gums around Brisbane that I have noticed are more inclined to fail in storms than others ...

1/ Eucalyptus racemosa (Scribbly gum)
2/ Eucalyptus major, Eucalyptus propinqua, Eucalyptus punctata (grey gums)

Occasionally ironbarks do fail too however that's more so due to the poor branch unions (codominant included unions) which can in some of them be a problem throughout the canopy ... each tree on it's own merits though.

So for your trees specifically we'd need to see the branch architecture, unions, canopy weightings, growing conditions, soil etc etc .... pictures pictures pictures.

The phenomenon of SLD (Sudden limb drop or Summer limb drop some call it) is a little better understood these days.

SLD primary cause is wood embrittlement due to heat and drought (lack of water). The problem appears to affect the longer more horizontal branches.... which you tend to find lower in the canopy as they over extend to get sunlight due to the shading from branches above them. The problem exists across a broad species of trees not just gum trees.

Attached is a PDF of 2 reports, up to page 18 is one guys report then another after that. It was obviously prepared for Council because it was a large gum tree dropping limbs in South Australia ... gives you an idea of the process.

Attached Files

SA-Significant-tree-reports-2-parties-compare.pdf (2.49 MB, 592 views)

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newguy18

I get that too,we also have some of the smaller ones just topple over,no sign of rot.Most of the trees that shed limbs though,its usually either rot,or wind that causes it,the big oaks also seem to havs a natural lion's tail going on,so when pruning i like to reduce the end weight on heavy branches to help out.

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old schooler

Bernard Keays

Kazigarden,

Ekka is quiet right here. We need a positive identification on the tree before making any judgements. Its important for Arborist’s to be able to identify trees as each species has different characteristics.

I’m not familiar with trees in your area but we have a number of trees in our area which people commonly call ghost gums. Ghost Gums occur in Western Queensland, Northern Terrority and North West Western Australia. They are not widely planted in coastal areas of South Eastern Queenland. However, we do have some gums which are commonly mistaken for ghost gums.

They are...

• Eucalyptus racemosa (scribbly gum)

• Eucalyptus grandis (flooded gum)

• Eucalyptus saligna (Sydney blue gum)

• Eucalyptus tereticornis (forest red gum, Queensland blue gum)

• Eucalyptus seeana (narrow leaved gum)

• Eucalyptus alba (salmon gum)

• Corymbia citriodora (lemon scented gum)

• Angophora leiocarpa (smooth barked apple)

Could we encourage you to post some photos of the tree including the foliage, root plate, trunk and scaffold branches?

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Bernie

TrevMcRev

Good reports there. The first i dont really agree with the out come though. Why cant it be crown reduced? My impression is that the writer, a botanist, perhaps doesnt have much/any hands on experience as a practising arborist. While the report is nicely written and factual, it falls down when it comes to putting anything into practice.

The second one, i am very impressed with. Well structured, well written, and a very real and possible solution in performing crown/weight reduction. Many an arborist struggle with getting the dosage of pruning right that is required to successfully perform this type of work. I think this guy has it nailed.

Still, no one really actually explains sudden limb drop as being something that just happens.

I believe it still has more to do with a trees architecture, or structural design if you like, than being some strange phenomenon.

End weight, leverage, length/diameter ratios have more to do with it than anything else.

It is easy to lose scale of things in very large trees like mature River Red Gums. Branches that, in the scheme of the whole tree might appear fairly minor, when looked at objectively on their own can certainly be pushing the limits of physics in terms of design.

I am interested in any documented scientific evidence on why it happens, but i keep coming back to the fact it always seems to happen to branches of poor structural design.

The failure on a calm day thing seems to be the instigator behind this theory. However, like the writer of the 2nd report, I have analysed many such failures, particularly in River Red Gums as they of interest to me, and seem to be one of the main species the finger is pointed at on this subject, but have always found a sound explanation. Often some earlier wounding in the area of failure, on a branch design that pushes the limits of physics.

This species can survive few - several hundred years with this behaviour just fine. It works for the tree. It works for the fauna that reside in its hollows created. It just doesnt work when humans decide they want to live right under or near the canopy of it.

Then a redesign of the trees architecture is required. One that reduces the loadings on individual branches and major stems as a whole. When a trees design is kept well within the limits of physical failures then perhaps, just maybe, branches wont suddenly, mysteriously or visciously fall from the evil tree that is out to get you!

Understanding species individual dynamics helps to judge the merits or faults in a particular trees design.

Anyone who has worked on large mature River Red Gums would know how they react and release cut parts. The loadings on them is massive.
The release of major branches is very quick with minimum shallow cuts. POP! When you cut one i cant help but to wonder just how much more load it could have supported.

TrevMcRev

Another thing i think behind the "gums just drop branches" fear is purely statistics.

Think about it.

If in Australia, a branch happens to fall off a tree for any reason, chances are it was what species???

There are probably more gum trees in this country that every other species combined.

So, while i believe 99%+ of failures of any significance are for an arboriculturally explainable reason, chances are, if a branch did fail, it belonged to a gum tree......

If people consulted arborists on a regular basis to inspect their trees health & structure, most failures could be avoided if the appropriate actions were employed. Be it crown/weight reduction, cabling/bracing or removal.

Eric Frei

A hypothesis is that transpiration is shut down by the tree on such days loading the tips more with weight of trapped water.

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Sean Freeman

Trev you are quite right there is a distinct lack of any real scientific work on this so often quoted "phenomenon" here is Schwarze's opinion on the topic:

Trev get yourself his book if you have the cash...it is a fabulous resource that provokes more questions than it answers but the scientific method and the integrity of the work is an addictive read.

Eric Frei

From the PDF attached

Attached Files

summer branch drop.pdf (32.6 KB, 120 views)

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jmcg.insight.gardens

I can add a humble observation of large sudden limb drop from a purely horticulturalists viewpoint as I have witnessed the phenomenon first hand. I,m not an Arborist, but I had at the time concerns for some time about this particular tree.

The scenario was a large mature Angophora costata at Point Clare when I was there working. I had just mown that section when a limb measuring about 1500mm circumference just dropped with no sound. No pop, or crack as you would expect to hear, just the sound of impact.

It was a hot still day. The tree was in what I considered poor condition due to a restricted root system, as half of it's drip line area was covered with fully sealed road and it was as a result suffering from extensive Longicorn Borer to half of the trunk as it did not effectively combat this infestation with kino. So much so that I believed it was compromised in health and had asked for it to be checked by the Arborist prior to this hoping for removal, as I was concerned for the general public that visited there. This didn't happen.

It was not a drought situation and I believe that water stress was not a factor at this particular time, apart from the fact that it was a very hot day. The limb that dropped had no damage from insect apparent, or previous stress fractures and evidenced no darkening of the cambium indeed anything to indicate that it was caused by external nor internal forces and appeared in good health, the right colour, odour etc. The limb end was not jagged but looked as if it had just cleanly separated from the rest of the branch.

The most obvious feature of this branch in my humble opinion that contributed to it's demise was that it was a large, long, lower, over extended limb growing horizontally, of great weight.

When I grew up I was taught not to camp under Gum trees. They drop branches.

I spent a lot of time in the past talking to one of the older Cedar Getter's whom I was fortunate to be friends with at Upper Five Day Creek via Comara. A wonderful gentleman whom loved to spin a yarn and share his knowledge. Which regarding felling large trees was considerable. I knew him when he was 92.
Frank Supple (featured in the book Tree Stories by Peter Solness) was born in 1904 and lived his life felling Cedar and mill-able trees of great size, in a past era. He had the opinion that Gum trees were Widow Makers, not to trusted as they dropped branches. He was adamant on this point.

I believe that SLD is caused by structural defect or other factors,but drop their branches suddenly, Gum Trees certainly do. As such they are to be given consideration due to this when they are near houses, parking areas or any where that they will take out a target. Councils need to get it right on this point, there are many more suitable species if a Gum poses a threat to human life, and owners of large Gum's close to the house (like me) need to have them regularly checked by an Arborist for structure and disease.

glennak

Most of the sudden limb drops I have seen are red gums. River Red Gum is not a strong timber; strength group S5 (the second lowest). These trees often have long horizontal branches with the foliage on the end and poor branch taper.
Looking at old breaks it is often hard to find faults but often on fresh breaks on many types of trees you can see older cracks from storm damage that had weakened the branch and at some latter date the branch falls.

TrevMcRev

I agree with what you said about Red Gums. And add to it that i also think part of what throws peoples judgement of over-extended, end-heavy branches off on these is the scale of the whole tree.

When you look at the big mature ones, you can easily lose perspective, not thinking much of the "small" branches. In reality, those "small" branches when focused on in isolation are actually quite large and often over-extended, end-heavy branches with poor taper.

When you've worked on these a lot, you realise a few things.

When cutting, these branches release real quick, a little nick of an undercut, a little bit of a top cut & SNAP! As a climber you KNOW the branch was "snappy" And then ask the guys on the ground how "small" that branch. Bugger me, it was BIG. And real HEAVY.

At the end of the day, trees aren't immune to the laws of physics.

While they have an astounding ability at times to push those laws to what seems to defy physics, there is a limit. The universe won't allow things to defy universal laws....not for the long term anyway.

I'd like to see man engineer a 15m long beam with 200kgs of weight leveraged out on the end in the shape of a windsail, putting a 3000kg load on an un-cantilevered attachment point, just a small gusset about 20cm deep, bearing in mind the loads displaced at the attachment point will be multiplied many times further by additional forces in variable directions during periods of wind, rain, heavy seeding etc.

Picture a horizontal powerpole attached to another pole at the top, on the side by a small bracket with a medium sized billboard truck hanging of the end of it.....

Would people be suprised if it ever broke???

And some people think Weight Reduction Pruning is a farce...

I'm pretty sure a shorter lever-arm with a lighter load & less sail area has a better chance of staying within the laws of physics and would be less likely to fail in either still or windy conditions...but maybe i'm just CaRaZy

Now, with no target, who cares. Let the tree be. But if there is a target, and you'd like to help prevent it from being struck, you need to manage the canopy & health of the tree.

Or maybe Gums are just an evil species that dont believe in marriage, and exist only to drop branches when we least expect it, all part of their master plan to eliminate husbands from their wives, making widows....

Eric Frei

And in-light of Trevor's profound analogies I offer a 2008 post ...


Self Optimisation or Self Destruction

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jmcg.insight.gardens

LOL.........that's funny.................

you might be on to something there, worth thinking about. That makes me safe when you think about it and all you guy's are going to have to watch out..... maybe why that branch missed me.

The rest of the post was well thought out and eloquently worded....

you have to admit Ekka, that branch was Way over extended even to my untrained eye. No way I'd pitch a tent under that.

I suppose that the real problem is the general ignorance of the public to these issues with trees, if they knew more, they would be giving you guy's a lot more work in the area of checking trees first, for safety issues, rather than calling you out when the tree has fallen on their house.

TrevMcRev

Exactly.

You can't expect ignoring a tree for 50 years, or at least, never having an expert inspect it to be a good way of preventing failures.

Then when a failure happens it was just because it was a gum tree and they just drop branches.

Its like driving around for 20 years without servicing your car then when the engine blows it was because it was a holden and they just blow up.

Or eating crap food, smoking & drinking to excess all your life, never seeing a doctor & wondering why you had a heart attack.

Anyone with a large tree of any kind, gums included, within striking distance of a target of value to them is foolish not to $PAY$ an arborist to inspect & advise on their tree.

Hoping you will get the right advise out of a free quote from the larry the lopper could be the most expensive mistake they make.

The doctor won't come to you for a free medical, neither will the mechanic, but the tree guy......yeah they do free "quotes"

jmcg.insight.gardens

Yeah agree, have the same problem in the gardening trade, or when I worked in the plant nurseries. People expect you to give free advice, then don't take it. Then the look of horror by some people when you give a quote, like you cost that much for a gardener?, we do the same amount of study as other trades.

Sometimes I wondered why I bothered. Sometimes felt like I was just wasting my time over and over...........

Horticulture is such a frustrating trade at times, but I love it.

I was asked by an Arborist the other day if I knew what an Arborist does, and I felt like saying Yeah, save people from their own stupidity with trees. But I had to keep quiet as the public were present, meeting with some Concerned Residents. Needless to say I kept the residents well away, after all we had lobbied for the tree removals, they were dead trees and posed a safety issue. Just three large Erythrinas to go, and go they will, Council has given the O.K, can you believe it.

Sometimes though you get that gem of a job that makes it really worthwhile.

Been doing some reading "Grow What Tree" Australian Plant Study Group (Nelson, 1985) noticed in the lists section they have a list devoted to species that are limb droppers, namely : Angophora costata, Eucalyptus camalulensis. E citriodora, E. maculata. E mannifera ssp maculosa, E. obliqua, E. rossii, E rubida, E. viminalis. out of the numerous species we have of Eucs that is a pretty short list.

TrevMcRev

Hmmm....common limb droppers or just common trees????

Angophora costata, Eucalyptus camalulensis. E citriodora, E. maculata. E mannifera ssp maculosa, E. obliqua, E. viminalis.

In Melbourne, the above species are VERY common Eucs.

I nearly go so far as to say that throw in E. nicholii & they'd go close to making up the majority of Eucs in Melbourne gardens.

If there are lots of them, then chances are there are lots of them with poor structure that have never been inspected or had a re-design of their structure.

glennak

Yes I'd agree Trev except they left out botryoides which is probably the worst if you don't count nicholiis bad forks.