Yew

[joachimM]

Note that also compression wood has a higher microfibril angle (at least in some conifers), which in turn reduces its modulus of elasticity (making it more supple, or rubber-band like if you want), and increases its strain tolerance.

As for compression tolerance, don't forget the importance of other wood components: high lignin content also confers better compression properties. Incidentally, this is also higher in compression wood.

There's been a lot of research on these topics, as high MFA also leads to less stable wood (torsion and other distortions), which isn't desired in timber.
Google "compression wood microfibril angle"

From a 2004 paper: "The large MFA in juvenile wood confers low stiffness and gives the sapling the flexibility it needs to survive high winds without breaking. It also means, however, that timber containing a high proportion of juvenile wood is unsuitable for use as high-grade structural timber."

How much juvenile wood there is: in some analyses rings deposited during the first 35 years were still considered juvenile. But I doubt a ring count is a reliable way to assess this. Still, there is a gradual change (in MFA) from juvenile to adult wood, not an abrupt one.

[E. Jensen]

No set number of rings.  I prefer the term crown wood, even though most use juvenile wood, because it doesn't really mean the wood is juvenile.  You could have 100 years of juvenile wood if a tree had 100% crown.  Much more to do with hormones associated with the crown, so it just makes more sense to me.

[DC]

From a 2004 paper: "The large MFA in juvenile wood confers low stiffness and gives the sapling the flexibility it needs to survive high winds without breaking.

I've wondered about this. Yew is an understory wood. At least Pacific Yew is. It doesn't normally get hit by the wind. Actually in a natural situation very few conifer saplings get hit by wind. They would always be protected by the surrounding trees. They may get dumped on as snow slides off the branches of other trees but wind, uh uh. The trees around the edge of the forest would feel the wind but I don't think they would effect the evolution of the species that much.

[joachimM]

I get your point. Saplings don't just get hit by wind, they typically are long and thin. If not very flexible, they would break too easily when bent in any way.
We may not know exactly why its wood behaves in a certain way, but it's been eons of evolution that made it the way it is. If it has certain features, there is probably a good reason for it, we just may not know yet exactly why.

When I see my fruit trees (apples, pears, cherries, peaches and so on), their branches need to be able to bend under the heavy load of the fruit in the summer and fall without breaking. Incidentally, these species make excellent bows as well, because they have similar properties as yew.

I like the way E Jensen put it as crown wood, makes a lot of sense to me: it couples the need for higher elasticity to the functional aspects of being wood that has to bend more.