Time of year
Certain plants require pruning at specific times of the year. For instance, hydrangeas bloom on wood that grew the previous year. That means if you want flowers, it’s important to only prune the plant immediately after flowering. If you prune at any other time of year, you risk removing buds. If you live in a cold climate, heat-loving summer bloomers like hibiscus should be pruned no later than mid- to late summer. Pruning initiates growth, so if you prune hibiscus too late, it will put on new foliage that could be damaged by frost. This damaged growth can result in no blooms come spring.
Periods of blooming
Generally, good times to prune are following periods of flowering and rapid growth. If the plant blooms more than once a year, pruning will often initiate it to re-bloom. Pruning right after flowering is also safest for those plants that only bud up once a year, because doing so helps guarantee that you don’t accidentally prune off latent buds.
Harvest
Giving many vegetable plants a minor pruning following harvest cleans things up and often initiates regrowth and blooming. Slightly prune back vining veggie plants like tomatoes, beans and cucumbers, and within a couple of weeks, you will often enjoy another flush of blooms. Only prune veggie plants back by 10 percent to 15 percent at a time. And avoid doing so toward the end of the season, as the plant may not have enough time to re-grow before frost sets in.
Dormancy
Most fruit trees and berry plants require pruning while dormant. Without this pruning, they will often experience a poor or even nonexistent fruit crop. Pruning fruit trees also helps direct growth. Dormant pruning applies to grapes; stone fruits such as peaches and plums; and berries, like raspberries, blackberries and boysenberries.
Following rapid growth
It’s often an ideal time to trim back after a period of rampant growth. Doing so keeps quick growers, like certain invasive vines, under control.