Eucalyptus leaf reduction ?

[PeterH]

Red Box ( Eucalyptus polyanthemos )


One of the qualities we look for in Bonsai is then ability to reduce leaf size. I have had success with nicholii by pinching back regularly. With others I have tried defoliation which has produced even larger leaves.

This Red Box was bought from a mature tree nursery about 4 years ago. I have gradually reduce the root ball and tried to instill some character into a somewhat straight boring trunk.

During this time the leaf size has been large. In October 2008 I tried a complete defoliation. The results were leaves as big as the palm of my hand. As new shoots developed to the length I required I pinched back the new growth and removed the larger leaves. This produced smaller leaves but still not small enough.

The pic shows (if you look closely ) various sizes of leaf. I am hoping that next season I will be able to reduce the leave size even more by the pinching method.


PeterH.

[FlyBri]

Gday Peter!

Nice work with your Red Box! I must say that looking at yours, I'd be half tempted to try the species again, especially if I had access to a specimen as burly as yours... My attempts thus far have been hampered by the large leaf size and small stock size available, and usually it seemed that the smaller the tree, the larger the leaf. Every E. polyanthemos I have tried has either ended up in the compost or planted in the garden. The leaf reduction you have achieved is really great, and my hat is off to you!

I believe I have mentioned before that I have never defoliated any of my Eucs as such: the only times they've ended up being leafless is when I've cut them back to re-pot 'out of season', or when I've been a bit lax with my watering... Sometimes the leaves have grown smaller with smaller internodes, sometimes the exact opposite, and I am yet to see a pattern.

...In October 2008 I tried a complete defoliation. The results were leaves as big as the palm of my hand....

Just for the non-believers among us, I've taken a photo for proof.

E_Polyanthemos_Leaf.jpg

After reading your comment above, I went and looked at the established Red Boxes I have in the yard and surrounds, and I made an observation that it is only the young ones which display such enormous, round leaves. The leaves of the older trees are generally much smaller, more ovate, denser and more strongly affected by gravity than the round leaf we are accustomed to with nursery stock. When I checked my Euc Bible, I came across an interesting and enlightening passage which seems to support my observation:

Some populations of E. polyanthemos...differ in the variably narrower adult leaves. This distinction is very variable within and among individual trees and populations throughout the range of E. polyanthemos, and appears to be related to crown maturity.

'Crown maturity', eh? It is an interesting - if very vague - concept that begs a few questions: What factors determine crown maturity for a Eucalypt? How can we tell if maturity has been reached (apart from the leaves indicating that it has)? Is it a state that might ever be achieved in Bonsai practice, given our tendency to continually renew our trees via pruning and repotting? Could it be that 'crown maturity' has more to do with the roots than with the crown itself?

Sorry for going off on a tangent, but I found these questions interesting to ponder.

Thanks, and please keep us posted on your progress with this tree!

Fly.

* Eucalypts of Victoria and Tasmania by Dean Nicolle, Bloomings Books, 2006.

[PeterH]

Fly

Thanks for the reply. Your questions are much the same as mine and it’s taking quite some time to come to a definitive answer for most of them.( Forever )

As far as leaf size goes, defoliation did not not work for any of my Eucs. I found on my nicholii (avatar) the leaf size on new shoots are relatively larger than the older areas. These new branches are allowed to grow into position and then pinched back. Over the ensuing season I regularly pinch back which reduces the leaf size and the larger ones are removed.

With this method I am yet to see if the Red Box will start to produce adult leaves (doubtful). Also flowering may not happen.

Again thanks for your input

Peter

[EdwardH]

Hi Peter,

I have had some small success with E. maculata by pinching out the new leaves with tweezers (similar to maples) when they were just opening. The leaves reduced to about 2 - 3cm long however if I got slack each new leaf on the branch would grow progressivly larger until it reached its normal size. Hope this helps.

[bonscythe]

Not a definate answer either but I'm sure it's something to do with the juvenile leaves paving the way for secondary growth in the plant. They are of a larger size so they collect more light for the plant, once the plant is into the secondary growth the leaves seem to reduce. Possibly the age/width/thickness of bark might be an indicator.
Did the suckers it produced have the juvenile leaves aswell?
I'm growing a bunch of Eucalypts and Corymbias from seed to see how they go in the long haul..
I don't think gravity is the reason the leaves of some gums seem to weep, something to do with whether the species has stomata on both sides of the leaf and the activity of the pulvinus on the petiole. I thought we had it tough, only gravity to keep us down..
There's gotta be more people who have tried the eucalypts as bonsai!

[jaketaylor]

Has anyone tried defoliating at different times of the year? Late summer or even winter when less sunlight is available.

I have no experience as yet with Eucs but I know they have a survival mechanism to push out new growth after bush fire. I believe this is from stored energy so it may be possible to trigger this mechanism in months with less sunlight and thus less availability of resources to grow big leaves.

Just a suggestion. I may be way off but it's worth experimenting with this genus.

[Rory]

How is this tree going Peter? They are a lovely tree the E polyanthemos.

I tried this species too, but its way too young to know any better yet. They have a beautiful look to them, and such unique and lovely foliage.

[Kevin]

Ah Jaketaylor,

You had me mate, a thread from the legends and beginning in 2009.

I was ready for 10 pages of good information - then it stopped.

Just noticed Rory's onto it - But thanks for digging this up.

Kevin