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How does a tree grow?

Started by dnalley, August 02, 2016, 09:42:57 AM

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dnalley

If you don't know, it doesn't necessarily make you stupid, but it does make me ignorant on this question.  Does a tree add layers on the outside, or to the heart?  If on the outside then why is the inner wood called"juvenile"?.  Seems to me that would be the oldest wood.  I know a barbed wire fence would say it's added on the outside, but judging from my own body, I seem to have grown from the inside out (stretch marks and such).  I know i'm not a tree, else I wouldn'the feel so old, but this is a genuine "wonder" for me.....and the heading says "ask the experts".  If you were looking at a butt cut, where would the oldest growth ring be, inside or outside?  Guess the "juvenile" thing has me stumped!  Thanks, Dwight


Ron Wenrich

The tree grows on the outer layer called the cambial layer.  It lies right under the bark.  There are phloem and xylem tubes that are laid down by the cambium layer.  The phloem are on the outside of the cambium, and eventually become bark.  The xylem is on the inside and become wood. So, the diameter of a tree is put on the outside of the tree, and is therefore the youngest wood.

Juvenile wood is more about tree age than about wood age.  Young trees grow faster in order to get into the overstory.  That fast growing wood is a bit different than the slower growing wood when a tree achieves its height.

The height of the tree is gained through the buds.  That puts on new growth and grows towards the light.  Some years the height is better than others, and most trees in the temperate regions only put out a season of growth in the spring.  That's when they lay down the spring wood.  In the summer, the tree is setting buds for next year.  That process puts down the summer wood, which is usually wider than the spingwood.  They comprise a ring in tree growth.

Looking at a butt cut, the oldest wood is in the center, which is also called the pith.
Never under estimate the power of stupid people in large groups.

dnalley

Thanks, Ron.  That exactly answers what I was wondering about, especially the juvenile part. I must say the answer was a lot more clear and concise than the question was.  You really have a way of getting to the point.

ppine

Good post by Ron.  The next concept to consider is that trees grow from the ends of the branches. (apical meristems, or terminals ends). If you hang a tire swing from a low branch, it is not moving during the life of your kids. The branch  will get larger in diameter, but will not grow up the tree.
Forester

Texas Ranger

Quote from: dnalley on August 02, 2016, 11:06:35 AM
Thanks, Ron.  That exactly answers what I was wondering about, especially the juvenile part. I must say the answer was a lot more clear and concise than the question was.  You really have a way of getting to the point.

By the way, happy birthday there, young man.
The Ranger, home of Texas Forestry

CTYank

More about juvenile wood: I've heard it said that the quality can be poor in plantation trees, trees planted en masse after a clear-cut. They grow very fast, with wide annual rings, compared to more mature trees that have to compete with their neighbors for resources like sunlight.
Seems that consistency of growth-rate is especially important for tonewood- raw materials for luthiers.
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WDH

All trees have a juvenile core.  Faster growing trees will have a proportionally larger juvenile core relative to the total amount of wood in a log.  The more mature wood surrounding the juvenile core that is put down as the tree ages, the easier it is to corral and tame the juvenile wood in the core because you can put the juvenile wood in the center of the board with the mature wood on either side.  If it is a relatively young tree, like from a fast growing plantation, it is harder to do this because there is not as much mature wood on the stem. 
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dnalley

I really appreciate all the answers to my question.  Even to a mind like mine, these answers have helped clear up some misunderstandings that I have had.  I still think that the word "juvenile" is  misleading in it's usage.....if it's been there longest, it's "oldest", BUT now I have an understanding of the bigger picture.  After all, there's probably no other language in the world that's more confusing than english...example "flamable"...."inflamable" and others I can't think of right now.  Again, thanks.

WDH

It is juvenile wood because that portion of the tree was juvenile when the wood was put down  :).  It was just young and spry  ;D. 
Woodmizer LT40HDD35, John Deere 2155, Kubota M5-111, Kubota L2501, Nyle L53 Dehumidification Kiln, and a passion for all things with leafs, twigs, and bark.  hamsleyhardwood.com

samandothers

Quote from: WDH on August 09, 2016, 03:41:24 PM
It is juvenile wood because that portion of the tree was juvenile when the wood was put down  :).  It was just young and spry  ;D.

A mere sprig?

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