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Heartwood formation and eucalyptus

Monday, November 26, 2012, Dean Satchell's blog

Denis Hocking emailed the EAG committee with this on 26 November 2012:

Hi folks, Just a note on E. longifolia. Knocked over an 18 yr old specimen yesterday hoping to get some posts out of it. Only got firewood, hardly a hint of heartwood. It was a somewhat suppressed tree up on a dune, so not a top specimen, but disappointing. So cut down an adjacent E. globoidea of similar size and also suppressed, only about 3 growth rings of sapwood so plenty of heart. Don’t know how general this might be for E. longifolia.

This appears to be general for symphyomyrtus group species. Although my experience is limited I have found this applies to E. saligna, E. longifolia, E. quadrangulata and even E. bosistoana (although I’ve only cut down two 10 year old trees). There seems to be a certain age where symphyomyrtus species suddenly put on heartwood. I’d guess 25 years. I thought I had heartwood (appeared that way) in a 8 year old quadrangulata but 5 years later the whole thing was rotten. Not so with 12 year old E. macroryncha (stringybark, monocalyptus group), 5 years on the ground and the heart is still sound while the sap has completely rotted away. 10 year old E. sphaerocarpa (monocalyptus) only has 1 cm of sapwood and shows why the EAG needs to continue our focus on monocalypts and stringybarks. Of course there is also E. cladocalyx, a truly remarkeable species for heartwood, the symphyomyrt exception but not really related to what we know as symphyomyrts.

One of Jim Coxes 25 year old E. longifolia had fallen down recently and we cut it open, the heartwood content was reasonable. Ten year old thinnings had no heart. Ben McNeil just dropped a few 10 yr old quadrangulata and sent me some pics because he couldn’t see any heartwood in these, which aligns with my experience. Monocalypts have a narrow sap band. Even at 25 years saligna has a big sap band, frustrating for the saw miller, who wants red heartwood!

One post

Post from McNeill Trust on September 10, 2013 at 8:11AM

I cut some trees today to look for heartwood for post use. 10yr microcorys had basically no heart at all, just a hint in the lowest part of trunk. 10yr pilularis (monocalyptus) in same stand had about 60-70% of diameter as heart.

In another stand I cut down one each of 20yr maidenii, saligna and globoidea (all symphyomyrts). Maidenii had good heart at the base, but none at all by halfway up trunk. Saligna was better, with small amount of heartwood still visible about 75% of trunk height. The globoidea (monocalypt) had only a few mm of sap at ground level, and near the top of the tree a cross section about 50mm diameter under bark still had near 50% heartwood. The cross section was totally different from maidenii and saligna.

In another stand I cut down a 10yr propinqua (symphyomyrt). Only a very small amount of heartwood. Then I cut a 3yr old coppice from 10yr total age muelleriana (monocalypt). It had about 50% diameter as heartwood. Far more heartwood than the 10yr old microcorys!

Deans observations seem to hold true for this very small sample; monocalyptus have much more heartwood as young trees than the others.


Waimarama HB

Disclaimer: Personal views expressed in this blog are those of the writers and do not necessarily represent those of the NZ Farm Forestry Association.

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