I have been reading about how to prune grape vines and olive trees, and in multiple occasions it is recommended, when performing a cut, to leave a short collar from its base, (possibly in proportion to the diameter of the branch being cut, usually around 1-2cm), for these two reasons:
- to avoid inner branches from drying up, since as the sap-flow retraces, branches at the edge might be left outside the (modified) flow.
- to protect the base branch from fungi and parasites in general, as the small leftover protuberances drying up, are unattractive for parasites, so it performs a function similar to the bark.
Is this correct? Can this be considered a rule (of thump) that works on many plants of ligneous structure?