Many ornamental shrubs are pruned in Spring but there are two different reasons for doing so and it helps to understand how different plants grow before you reach for the sharp tools.
Shrubs that flower in winter such as Witch Hazel or early spring like Forsythia need to be pruned just after flowering if you want to restrict the size. This is because they flower on wood that grew and matured the previous summer. Pruning in spring allows the maximum time for the shrub to grow back to the desired size and produce mature flowering stems for next year.
Shrubs that flower in mid to late summer including Roses and Hydrangeas flower on stems that grow in the current year. These are pruned in March just before growth starts and they have enough time to mature before flowering from June onwards.
Either way, you can keep your shrubs at a stable size without losing flowers.
If you would like to understand the why & how of pruning small trees & shrubs, take a look at my Gardening by Design ‘Box of Tricks’ video topic: a whole hour of video tutorial, just like a one-to-one lesson with explanations, summaries, photographs & a few diagrams. It is divided into 3 videos with breaks so that you can watch a section and then apply it in practice.
Happy Gardening, Alison