The question of how to prune Grevilleas is a vexed one. Grevilleas do need pruning however they respond differently.
The answer depends on what sort of pruning and what sort (species) of Grevillea you are going to prune. Some you can really only tip prune, or prune very lightly, other you can semi – hard prune.
One common factor is when to prune Grevilleas. ALWAYS when the plants are in active growth, and never in cold weather. So wait until spring has settled in and the danger of a cold spell is over. However Methods do differ.
Pruning Methods for Grevilleas
Tip Pruning Method
You can do this in spring when the sap is rising, its a simple matter of pinching out the tips to make encourage bushy growth. Chances are if you do this from when you first plant them you will may never need to try the second method.
This means cutting back to existing growth from 30% to 50% off the plant. This can be carried out every 2 – 3 years. Best to prune back to branch junction or look for a bump in the bark.
Not really recommended at all as hard pruning can kill grevilleas. However sometimes its prune of replace.
Once grevilleas reach maturity they can require a dramatic chop or replacement. And this is where the species will determine what you can do. Grevilleas have epicormic buds, but not many of them and some more than others.
The Banksii forms and the hybrids MAY reshoot from these buds that are lower in the trunk, however they MAY NOT. So if you are desperate, you could cut back to the ground, however chances are you will k ill the plant.