Even though it's freezing cold outside today, it won't be too long before we will need to go out into the orchard and collect some pecan scionwood. The other day I cut down a young pecan tree (a really poor cultivar!) and it gave me the opportunity to cut off some pecan branches so I can show you how to find and select quality scions.
Let's start by looking closely at a pecan branch. The best scions come from last year's new growth. In the photo above, you can see 2-year-old wood on the left and one-year-old wood on the right. Two-year-old wood is generally more grey in color and all the primary buds are missing. The reason 2-year wood has missing primary buds is because last spring, these buds opened and produced catkins. Two-year wood ends in what is called the annual growth ring which is actually a ring of closely spaced bud scars. One-year wood has a more brown or reddish-brown color with primary buds still firmly attached to the stem. Note that the first few buds on the 1-year wood are small and you don't see a prominent primary bud until about two inches up the stem. When I cut scionwood from a tree, I take only 1-year wood and make the first cut just above the annual growth ring.
When I'm grafting, I can always tell if a scion is going to make a successful graft based solely on the ratio of wood to pith. The scion with a lot of wood and tiny pith will always out-perform a scion that's mostly pith. In cutting scionwood I always discard the terminal piece for two reasons; the buds are too close together and the stick is too pithy. In looking at the scions above, I'd choose to graft with the two sticks on the right. The second stick from the left is marginal and I'd use it only if I've run out of other scion choices.
Remember, when you are cutting scions, you don't need to slice into each piece to check the wood to pith ratio. Simply look at the cut surface at the top of each scion and note the diameter of the pith as compared to the overall diameter of the stem. The pith diameter should be no larger than 1/3 the diameter of the entire stick.