Why is sweet chestnut so hard to dry?

[woodyguy]

Well I might just take up the challenge of that experiment. I've got to cut down a couple of Sweet Chestnut on Sunday in my wood which will be used for firewood so not a big deal to test it out. Just need to remember to monitor them over the next six months. How long do we feel they need to be cut before we lop the extra inch off?

[spiral]

6 months would be good...

 

spiral

[daltontrees]

Well I might just take up the challenge of that experiment. I've got to cut down a couple of Sweet Chestnut on Sunday in my wood which will be used for firewood so not a big deal to test it out. Just need to remember to monitor them over the next six months. How long do we feel they need to be cut before we lop the extra inch off?

 

Hey, that's quite exciting.

 

I just had a quick surf of the net for any relevant publications. The ony one that jumps out is one that says "Tyloses form in xylem vessels in response to various environmental stimuli, but little is known of the kinetics or regulation of their development.

 

"Preliminary investigations indicated that wounds seal quickly with tyloses after pruning of grapevine shoots. In this study, tylose development was analyzed qualitatively and quantitatively at different depths and times from pruning cuts along current-year shoots of grapevines at basal, middle, and apical stem regions. Tyloses developed simultaneously within a single vessel but much separated in time among vessels."

 

Maybe the thing to do is to find the answer to your own question by monitoring the moisture content of all of the logs but re-trimming one or two logs a month. You might then get a different drying weight for each log that can be compared with its re-trimming duration. You might not only prove the tylose theory but could quantify how long after felling the tylosing reaction continues.

[ArthurBottlesworth]

Do you think its anything to do with climate

 

Sweet chestnut seems to like hot dry summers in s of france, perhaps ability not to lose water is important .......

[daltontrees]

Do you think its anything to do with climate

 

Sweet chestnut seems to like hot dry summers in s of france, perhaps ability not to lose water is important .......

 

I think it is said of Castanea sativa that it was introduced to Britain by the romans as a source of nuts but that it isn't warm enough here for the nuts to develop well enough to be a useful food source. So they seem to be able to do well enough here in damp cooler situations, living for hundreds of years. See post to follow about tylosis and maybe you will still think that it is something to do with climate.

[daltontrees]

I had a good root about in my library last night for stuff about tyloses. If anyone wants to have a look a ttheir own books, Shigo's Modern Arboriculture is quite astonishingly clear about them.

 

The gist is this. Firstly there are broadly 2 types of hardwoods, there is ring porous and there's diffuse porous.

 

Ring porous trees develop a few large new water conducting vessels in the new wood in spring and use these to conduct huge amounts of water to develop new foliage. They use only this year's ring and last year's ring for water transport. The previous 8 to 10 years' rings are used mainly for water storage but not transportation. Further back, the old wood is converted to heartwood by tylosis and by the secretion of gums, tars and other chemicals and by the cells effectively dying.

 

Diffuse porous trees develop many smaller vesels in new wood and keep doing so all summer. All rings, old and new, are used for water transport. And here's the crucial point. Diffuse porous trees do not develop tyloses.

 

Secondly (bear with me, I'm aiming to get to a punchline as quickly as I can), tyloses develop into the lumina (the air space) in dead water conducting vessel cells from adjacent living parenchyma cells. Those cells are the ones that also produce the gums and tars. It is an active process by living cells. When they're dead they can't do it any more.

 

OK, I was relieved to find out that Castanea sativa (Sweet Chestnut) is indeed ring porous and can develop tyloses. But we can also expect about 10 years' worth of rings of wood to be well adapted to water storage. And beyond that we can expect permanently tylosed closed-off gummed up heartwood which if it contains any free water will be locked in.

 

Still with me? Good.

 

So when Sweet Chestnut is cut into logs, the living cells will live long enough to produce tyloses and block the ends of the water vessels, trapping the water in. How long will it live? I would have said a few weeks, maybe a couple of months. After that it won't be able to produce new tyloses or gums/tars to block vessels. Meantime it's business (or lack of it) as usual for the heartwood, it will be slow to lose any water it has.

 

So, the re-trimming might work well for the outer 10 years' of rings to release trapped water. That's about all I can think to add just now. Except that I see Sweet Chestnut cut open so infrequently that I cna't recall whether the heartwood forms after 10 years or some longer period. I am sure this 10 year 'rule' varies a lot from species to species. Does anyone out there know what it is for Sweet Chestnut or any other species like Oaks, Robinias, Elms?

[woodyguy]

Thanks for informative post. I've been cutting 80 year old SwC recently and the sapwood is about 10-15 years. Fairly similar to oak of same age that I've also been cutting. I'll actually formally count them at weekend to see.