I frequently read tips that recommend the ideal time to prune a plant is when it is “dormant.” How do I know when a plant has gone dormant?
Dormancy usually refers to the time that the leaves drop off and lasts until the plant leafs out in the spring. For many plants, the best time to do any major pruning would be in early spring before it starts leafing out.
Trees such as birch and maple are usually better pruned in late spring when the plant has fully leafed out. Otherwise they have a tendency to “bleed” sap at the points where they were cut. Evergreen trees are best pruned in late spring just before the “candles” of new growth harden off. As you can see, it is more important to know what kind of plant that you need to prune, and not to just prune anything just because it is dormant, because many plants will break that “rule.”