Scions in the Forest Garden:

When grafting, both the rootstock and the scion transmit specific growth characteristics when joined together. The scion a farmer chooses to graft onto a rootstock will then determine the type and quality of fruit produced, the time of year the fruit will ripen, the vigor of the top growth, and the top growth’s ability to resist pests and diseases. When selecting a scion for grafting, it is recommended to use a stem that is roughly 10-12 cm long.

Additionally, the scion should have a terminal bud that is lignified  (rigid and woody) and swollen but not yet sprouting. If the bud has already sprouted, the graft point will not take and the scion will die off. If the scion is not lignified, it risks drying out.