Juvenile wood

[E. Jensen]

Juvenile wood is the wood that forms in the first 10-20 rings from the pith.  It is always forming, because even after mature wood starts forming near the base, there is always juvenile wood forming towards the apical meristem.

Juvenile wood is inferior to mature wood in ever aspect except some niche paper products.  It has more lignin, lower density, less strength, higher tendency to form spiral grain, and more longitudinal shrinkage and warping due to the higher microfibril angle in the S2 layer of the cell wall (cellulose chains are at an angle, not straight up and down).  Juvenile wood is a big problem in the wood industry, and I was curious how it has affected bow making and if anyone has any insight.

Usually in bow making this is not a problem since a lot of staves are split from older trees.  A big reason I think is juvenile wood is associated with wood formation of the stem within the crown, which is associated with knots, and bowyers generally avoid knotty wood, and go for the knot free wood which is coincidently likely to be mature wood.

But I was thinking about this elm sapling I have drying, and sapling and branch bows in general (lots of juvenile wood in branches and compression wood as well, which has its own suite of negative effects) , which can quite likely be less than 10-20 years old.

[George Tsoukalas]

I did not understand a lot of your post but I have made sapling bows and I'll guarantee I am not the first. They have probably been made for millennia. Jawge

[DC]

Does this also apply to sucker wood? I'm in particularly referring to  the shoots that sprout from a stump(coppice is the term I think). That stuff can grow at tremendous rates and a shoot can easily be bow sized in 5 years. Maple does that around here. In England they have coppiced Hazel for centuries. It grows so fast and straight that it can be almost knot free.  Sorry I'm kind of rambling

[E. Jensen]

Hmm I'm not sure but I can find out.  I wonder if that would be similar to pollarding, which is like coppice but up top.  Real popular in the UK, and real ugly too.

[DC]

I'm guessing that because pollarding can produce so many shoots that the individual shoots would be smaller. With a coppice you get a lot fewer shoots and with the entire root system feeding them they grow way faster. I agree. Pollarding is ugly. Our main street trees are either pollarded or poorly pruned, I haven't decided yet.

[George Tsoukalas]

Suckers make bows too. One of the best bows i made was from an osage sucker. Jawge

[E. Jensen]

So I just got done talking to my wood tech professor and he wasn't sure either.  He thinks that coppice and pollard shoots form juvenile wood, since juvenile wood is determined by the age of the cambium, and shoots start from fresh cambium he thinks.

[blackhawk]

Go cut and make a few dozen sapling bows and come back and report here...I have and can tell ya what I think of them. Science schmience blah blah blah. We think we  know and have all the answers,but we still are no smarter than a tree IMO. In bow making real results and experiences will tell you more about bending wood for bows than your professor can tell you or anything you read in a book or online       

[E. Jensen]

That's why I was asking you guys about it.

[Drewster]

Your description of the location of juvenile wood tells me it's heartwood......and that after ten or twenty years, that heartwood changes to be comprised of mature wood.  Is this the case?  If so, then as heartwood continues to increase in a tree, it is mature wood in the outer rings rather than juvenile wood that comprises the inner rings.

Ten to twenty years seems like a wide range of time for the change over from juvenile wood to mature wood.  What triggers this change?  How can you tell if heartwood is juvenile or mature?

Most all of us have made sapling bows at one time or another but most bowyers I know work with staves or billets from trees a bit older......where the limbs of the bow are likely made from wood fifteen years old or more.  So, hopefully your concerns here are inconsequential for most bows.  Thanks for sharing your knowledge of wood technology.   The more us bowyers know about wood technology, the better bows we can hopefully build......so stay away from juvenile wood where it exists.

[E. Jensen]

Juvenile wood is different than heart wood.  It eventually becomes heartwood as well, but will always remain juvenile wood and will never become mature wood.  The reason the range is so wide is because it depends on a lot of things.  Its variable between species and within.  It has to do with the crown and hormones released by it.  Its a very complicated phenomenon.  It's also been referred to as crown wood, which is how I think of it, and the most basic simplification is that its wood formed on the stem within the crown.  So if a stand of trees self thins due to close proximity to each other, the crown will be raised sooner and it will start forming mature wood sooner.  If you have an open grown tree, with a crown ratio of 100%, touching the ground, (think christmas tree) theoretically it would be 100% juvenile wood, as well as riddle with knots and quite a bit of taper.

As far as I know the only way to tell for sure is a microscope

Functionally, I WOULD say just avoid the center core of trees, the first 10-15 rings, but I've not heard any bad things about using that wood, which is why I came on here to inquire.  I'd also say avoid compression wood, which is also considered inferior, but people have reported decent bows from that as well

[son of massey]

You said you like to think of it more as crown wood, and for a lot of sapling bows people do take a bow length stave from somewhere near the bottom of the tree, which usually means a bit of the very top of the tree gets cut back, so maybe by the act of looking for a halfway straight bit of wood we select against this juvenile wood?

If the inner part of the tree was always juvenile wood and never any good decrowned small tree staves should make for poor bows and this is not generally considered true. Whether juvenile wood doesn't matter much or we avoid it without knowing about it, it seems like a bit of a nonissue to me.

SOM

[E. Jensen]

That seems to be the case . . .

As long as there are branches with foliage on them, its crown, even little ones that might be on the middle of a sapling.  That also depends a lot on the species and growing conditions.  I'm also not sure how long it takes after the crown is removed before mature wood is formed.  If I recall, the transitient is a gradient over several years.  And like I said, that is the most basic simplification of it.  Its like photosynthesis.  Everyone knows its water plus CO2 plus sunlight, but its infinitely times more complicated than that and even with a forestry degree, I only know enough about it to understand that I really really don't. 

[joachimM]

in yew, the juvenile wood has the best compression strength properties (have a look at this post I wrote earlier: http://paleoplanet69529.yuku.com/topic/61477/Mechanical-properties-of-European-Yew#.VU02YvntlBc), possibly because of its higher lignin content.

As for other woods: I like to make sapling bows, but quite a lot of the sapling or branch staves (from coppicing) of the woods I work with (hawthorn, plum, scotch broom, ...) warp and check terribly in spirals, and one of the reasons likely is what you describe: because the angle of the spiralling cellulose fibers is greater in juvenile wood than in later formed wood. This is described pretty well in "The Wood Handbook as an Engineering Material"

Does that mean you should avoid it? Not if you can deal with those particular properties. Being more lignin-rich gives better compression resistance, so that would be a good thing.

anyway, that's my 0.02 €

Joachim

[E. Jensen]

hmm I'll have to look into that,  the higher compression