"Hardened" growth for semi-hardwood cuttings and air layers

[andrewiles]

I want to try some semi-hardwood cuttings and some air layers for my maples. I've read here and elsewhere to wait until the new growth is hardened.

I'm having a hard time telling exactly when that "hardened" point is. Hoping someone here can provide some clarity.

Here is a "Ghost Dancer" where the new growth from this spring has stopped elongating. The stem is still pliable but firming up a little. The leaves at the end of the stem are still enlarging.
My take: Still softwood, though nearing end of that window. Ok for softwood cuttings.


Here is a Sunglow vine maple. In this case new leaves are still emerging and growing. The stem is very pliable.
My take: Softwood. Good time for softwood cuttings.


And here is a Katsura. The leaves here have stopped growing, I think, and the stem has also stopped elongating. It is a bit stiffer than the other two but certainly flexible.
My take. Early semi-hardwood. Good time for semi-hardwood cuttings.

 

[Shibui]

I don't think the categories are rigidly defined as one class of wood ages it becomes the next sort so there must be some points where the stem is in between one and another. That does not mean you can't strike cuttings. There is a continuum of ripening wood and cuttings can still strike all the way through so rigid definitions are not really needed.
A definition I saw long ago involved bending the stem. If you can bend it right round 180 deg it's still softwood. If it fractures but does not break it is semi hard. If the stem snaps when you bend it is hard wood. You will obviously need to allow for the natural differences in brittleness of different species using this test.
I usually base my definitions on color change of the stem. If it is still the immature color it is softwood. If it has started to change color it is semi hard. If the stem has changed color to its mature state it is now hard wood.
I would normally be looking for semi hard cuttings later in spring or early summer but there will always be a range of different classes of wood on a stem during the growing season - soft at the tip, semi hard a bit further back and hard wood closer to the trunk.

 

[andrewiles]

I hadn't thought about stem color changes. That sounds promising; I'll take a closer look at the trees today.

Thanks for the feedback.