“When should I prune my….?”
If you don’t have an expert on hand to answer you can use this rule of thumb:
“prune straight after flowering”
The simple reason is that if you prune straight after flowering you can be certain that you won’t be pruning off the new flowers for next year*. This particularly applies to plants that flower only once a year. Some plants from hot climates flower for the whole season and usually the best time to prune is late April. This is for the reason that this plant are often quite tender and pruning them is best for them after any winter damage.
You might have noticed that many hardy garden plants flower in the first half of the year & others flower in the second half of the year. If any of your garden plants flower before the end of June the plant has initiated the flowers during the previous summer. Any winter pruning of these plants would remove the flowers for the following spring. You could prune most summer flowering shrubs in winter, you just need to remember which are which.
There is one exception and that is *Hydrangeas. They form next years flowers while they are still flowering in summer. This does mean whatever time of year you prune you will remove flowers or buds. If you need to prune Hydangeas either prune back a third of the shoots every year. For example if there are 9 stems prune 3 of them every year choosing them evenly, or prune the shrub down to around 15cm (6″) and accept one year without flowers.
The picture is Forsythia, a hardy, early spring flowering shrub ideal for most gardens.