# old vs. young (redwood growth)



## harum (Nov 25, 2013)

Until recently, when going through a stack of redwood at the lumberyard, I have always looked for lighter weight boards thinking that less weight means drier wood, which, in turn, means less shrinking, cracking and warping. But then noticed that the wood density has something to do with the thickness of the annual rings: thinner rings go with denser wood.

The board on the left side (22 rings per in.) is almost twice as heavy as the board on the right (4 rings per in.), the weight of the middle one being in between ( on the photo). I have read that thinner rings mean older growth, which means more stable and durable wood compared to younger growth.










My question then is: Would it be correct to say that heavier redwood boards would make a better lumber for exterior use, like backyard furniture and window trim? Or I should check the annual ring density rather than the weight? Does the weight have much to do here with the moisture content?

Would appreciate any feedback. Thanks and Best Wishes, h.


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## stevepeterson (Dec 17, 2009)

I saw a large cross section of a douglas fir tree somewhere. The center of the tree had huge growth rings. They got tighter towards the outer edge. So even an old growth tree has a range of growth rings ranging from very loose to very tight. I didn't know how to interpret the findings, since the heartwood has the largest growth rings and the sapwood has the tightest growth rings.

Any "managed" forest would have nothing but the fastest growing wood with large growth rings.


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## shampeon (Jun 3, 2012)

I think that's due to the mass that the tree adds per growth year, yeah? If a young tree add 1/4" of early wood, it would add X amount of mass. A mature tree adds 1/8" of early wood, and it adds 2X mass, since the tree is taller and the circumference is bigger.


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## jinkyjock (Feb 2, 2014)

+1 with *shampeon* in that annual growth rings may be tighter but the actual growth (mass) may be equal or greater than the previous year.
From my recollections of Wood Technology annular growth is governed by many factors,
climate (rainfall, sunlight etc.) being the main one.
Trees from colder regions tend to have tighter rings as their growing season is shorter,
these tend to be more stable.
However don't get hung up on ring size, direction is just as important.
In the examples you show I would use the left piece 1st, the right piece 2nd, and the centre piece would be my last pick.
1st pick-tight grain, 2nd pick (nearly) 1/4 sawn, centre piece would also have Tangential shrinkage.
But if timber is stored outside, even after kiln-drying, then it's total guesswork which way it will go.
It's all coming back to me now…...and I'm getting a sore head.
Good luck in your quest.
Cheers, Jinky (James).


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## harum (Nov 25, 2013)

Thanks for the replies, Steve, Shampeon and James! It's more or less clear why the annual rings get thinner with age. Here, however, it also looks like the density of the redwood also changes with age: it grows from the pith out. I think it may have something to do with differences in the densities and relative thickness of early and late wood within an annual ring.

Just to clarify: Old trees have both old (towards the sapwood) and young (around the pith) growth; and young trees' wood only has thick annual rings.

Appreciate the feedback. I guess, from now on, I will be looking for heavier redwood boards, which probably means older growth and tighter rings rather than a higher moisture content.


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## jinkyjock (Feb 2, 2014)

*Harum,*
I'm afraid you have it the wrong way round.
Trees grow on the outside in the Cambium Layer just under the bark,
not from the centre (Pith).
In each season there are two growth cycles, Spring-fast, Summer-slower,
and then the tree is dormant again giving a full growth ring.
If you look at a piece of timber (end grain) under a magnifying glass, it is self-explanatory,
as you can quite clearly see the differing cell size, imagine holding a bunch of different size straws.
If you take a cross-section (lengthwise) from the top of a still-growing tree,
it would resemble an inverted cone, as the tree grows out and up in each season.
I hope this helps, how a tree grows is a whole subject on it's own,
but my head is beginning to hurt again so I need to stop.
Cheers, Jinky (James)


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## harum (Nov 25, 2013)

Thanks for your message, James! Yes, I'm aware of where the heartwood, sapwood, cambium and tree bark are. Just as Steve said, the annual rings closer to the pith are thick-I think this is what's called "young growth"; the rings towards the outer edge are tighter/thinner-"old growth". "Old growth" rings are always younger than "young growth" rings. I thinks all these terms are getting confusing, not even sure this is the correct terminology, but what I have tried to say was that one could get "old growth", tight-grain lumber only from "old-growth forests", or "ancient woodlands" or, what it means these days, mature trees (which, of course, is not exactly true).

The actual science is more complicated than my simplified "theory". Online sources (e.g., http://www.woodweb.com/knowledge_base/What_Does_Old_Growth_Mean.html) suggest that for conifers tighter annual rings yield denser and more stable wood, which has more to do with growing conditions rather than age. For hardwoods, it is different: lumber with thicker annual rings is the same or denser.

This resource also suggests that the ring count alone should not be used as a criteria when selecting wood. Late to early wood ratio is more important. Just what James said. Thanks again.


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