Pruning Early-Blooming Shrubs
Shrubs that bloom early in the year, such as forsythia, form their flower buds the previous year. In the rush of the spring season, there are always so many chores to do it's easy to forget that these early flowering shrubs need pruning immediately after bloom. If you wait too long before getting around to it, you'll cut off next year's flower buds. And if you don't prune at all, these strong growers will quickly turn into giant tangles.
As soon as the last flowers fade, use a pruning saw to cut off one-fourth to one-third of the biggest, oldest stems at ground level. Use pruning shears to shorten all of the stems to two or three feet from the ground. If you wish to greatly limit the shrub's size, you can cut the branches as far back as six inches from the ground. By the end of the growing season, new branches will have formed. These will arch gracefully from the center and will be covered with new flower buds for next year's spring show.