AusBonsai

This is something I've been wondering lately so I thought I'd pose this question here.

Does mature bark on a Eucaplyptus/Angophora/Corymbia come with height, age or both? So if I bonsai a younger gum at around 30cm will it ever develop mature bark?

Teejay I only have one species of gum it is self sown seed now 4 years old about finger ( index ) thick approx 350mm high and the bark is peeling at the base.
It is the lemon scented gum. I believe it is now Corymbia ( formally Eucalyptus citriodora ). I am not sure if this is so with any other species.

Pup

Thanks Pup, I was interested in this because I recall PeterH mentioning something about mature bark on an E. Sideroxylon (I think) only being attainable at a certain height, so I wondered if that was the case across the board or only with certain types.

At any rate my Nicholii's bark isn't looking much like his.

Hi Teejay
I've grown a few eucalypts over the years and my experience is that they readily develop the mature type bark for their species. Some start the transition as early a 1-year old, while others take a bit longer. It seems that the 'gums', ie those that shed some bark every year and have 'smooth' surface bark, are the ones that show mature bark characteristics the earliest. I've had 'candlebark eucalyptus' (E. rubida) produce the lovely red colours at 2-years old, but then not show the red for several years after that. I don't know why the difference, as the bark is shed in typical gum-fashion each year. I had one snow gum that sheds its bark annually, changing from greyish to a lovely pale buttery colour, but none of the rich red-green-oranges that one classically loves in snow gums. My plant is from the high altitude form and is exposed to full sun and frost. So, I don't know what stimulates the rich colour - maybe just age. Mine is only around 15 years old, I think.

I had E. caesia sussp. caesia (related to 'Sliver Princess) produce that wonderful 'mini-richi' bark at 1-2 years old. E. kruzeana has fine rough bark in the lower part and smooth bark above, just as in mature trees - its some 20+ years old.

I've only one iron-bark (E. sideroxylon). It has peeled its bark as in gums from year one. After about 5-6 years, the peeling stopped close to the soil surface (say within about 5 cm of the soil). After some 10 years, the rough bark is now about 10 cm above the soil level in a tree about 50-60 cm tall. But even the rough bark still wanted to peel off this year. The rough bark is a lovely cinnamon colour, but there are as yet none of the very red-black and 'hard' bark that characterise iron-barks. When I've looked at mature iron-barks, I've estimated that rough bark starts to be produced on stems after about 7 years, and hard bark only after many more years, though by 20 years, the main trunk is pretty well covered in the classic hard bark. How long it will take to achieve this in a pot, I don't know. It would be good to hear of other people's experiences.

So, 'gums' come good with mature style bark very quickly, and the rougher barked forms take a while longer.
Hope this helps.

Cheers
Kunzea

Thanks again Kunzea, that was a pretty comprehensive break down of your experiences, and much appreciated. It looks as though, as with everything in bonsai, I've got to be bloody patient again!

As a side query, which euc do you most prefer, and at what height do you prefer to grow them?

R Kunzea,

My observations of the Iron Bark suggest that the mature bark does not start developing until the diameter of the wood reaches around 50mm. I have one I dug up in 2000 and is around 25mm in diameter. In spring I will be putting it into the ground for two seasons to try prove or disprove my theory.

Peter

Gday TeeJay, Kunzea and Peter!

Interesting topic... My theory is that the major factor affecting bark development is age, but I reckon there may be more to it than that. I've attached a number of pics which I believe represent mature (or semi-mature) bark on some of my Eucs. I'll give a brief run-down on each tree, and see if I can find a common thread.
This E. camaldulensis has been in my collection for most of my Bonsai life, and is about 10 years old. It has rarely been taller than 350-400mm (except when it was purchased as 500+mm tall tubestock). Its base is currently about 40mm across. I consider this bark to be semi-mature, as it still regularly sheds all the way to the base of the tree, whereas a mature River Red will tend to keep some lower bark intact.

* * * This E. melliodora has been in my collection for about 8 years, and is probably about 12-13 years old. The tallest it has been is around 1.5m, but it has usually been less than 1m in height. It is approximately 50mm wide at the base. Once again, I call this bark semi-mature: the top half of the trunk sheds bark in solid flakes, but the base is beginning to take on a fibrous appearance.

* * * I've had this Angophora floribunda for a year or two, and I estimate it to be about 5-7 years old. When I bought it from the nursery, it was probably about 1.2m tall, and has been steadily growing shorter over time. It is about 60mm at the base. I don't know what mature bark looks like with this species, but the flaky bark is very different to the bark on the tree that I layered off the top. Shall we call it semi-mature?

* * * I bought this tree about 2 years ago, and I was told that it is a River Red Gum (the leaves give me some doubts). I could not guess at an age, and I wonder if the tree is the product of an air-layer. When I bought it, it was about 1.2m tall, and I've layered and pruned it to below 1m (there's another layer on the cards too). It is about 80mm across. This bark is what I would deem to be mature: it splits and cracks, but does not shed. The bark has matured considerably in the past 2 years, as can be seen below.
* * * Finally, I collected this Euc in mid-2007 from a local garden. My paltry research points towards it being E. rubida (Candlebark), although I collected some flower buds and gumnuts this evening from adjacent trees which may indicate otherwise. It could be anywhere from 10 to 20 years old. Upon collection it was about 400mm tall, and while I was stalking it I never saw it taller than 1m (there is a lot of evidence that it had been chopped numerous times). Depending on where I measure, it is about 100mm across. The base displays very mature Euc bark which hasn't changed much in the past 2 years: occasionally it will swell and crack, exposing a red core, but it does not shed.

* * *

So, what have we gleaned here?

Of the very small sample of trees I've surveyed here, girth would certainly appear to be the major factor for the determination of bark character (as PeterH suggests). The problem is that girth can be achieved in a number of ways, including age, height, health, specific variation and/or a history of ongoing injury. (For reference, the bark of the tree in Case 4 is between 8 and 10mm thick at the top of the trunk (see below).) So, in answer to the original question, I have to say "yes and no".
If anybody else can see a pattern emerging here, please speak up.

Thanks.

Fly.

Thanks Peter and Fly, it's all very interesting and inconclusive isn't it!

Not knowing the age of Case 4 throws a spanner in the works as it's wide AND holds mature bark but we can't know what's contributed to it, the width or it's age.