one thing that all good bonsai have in common, is taper. having a tapered trunk and tapered branches gives a tree the look of maturity.
one common practice in achieving taper is by letting a trunk or a branch grow somewhat unchecked for a number of seasons. when the desired thickness is achieved, the trunk is often then cut back to a lower branch to form the new trunkline. and in the case of a branch, it is cut back to a bud closer to the trunk then regrow to give better taper.
however, there are some species of trees that do not readily produce back buds when cut back severely. this is when a low sacrifice branch can be encouraged to grow to thicken the lower portion of the trunk while the rest of the tree are controlled in their growth to direct more energy and vigour to the sacrifice branch.
This approach works especially well for pinus species.
to be continued…………………