Forsythias are one of those welcome signs of spring, a reassurance that warmer, sunny days are on the way. The branches of these deciduous shrubs with their bright yellow flowers are like rays of sunshine in the garden. My house came with one planted in the middle of a stretch of backyard. Planted in a row, they also make a dazzling hedge at the edge of my property, with non-descript green leaves filling in the space after the flowers have died back. In this article, I’m going to share the best time of year for pruning forsythia branches, and why timing is so important.
Hardy down to USDA zone 3, forsythia bushes are fast growing and reach about 10 feet (three meters) tall and equally wide if you don’t keep them trimmed. It’s likely you’ll want to prune your forsythia to maintain a manageable size. When planting, do be mindful of the eventual proportions you’d like your forsythia to be. This hardy shrub is also deer resistant and salt tolerant.
Forsythias are one of those spring-flowering bloomers with branches that can be cut in the late winter to force indoors—an even earlier harbinger of spring!
When is the right time for pruning forsythia?
Timing is key when it comes to pruning forsythia because if you leave it too late in the season, you risk lopping off next year’s flowers. You want to wait for your shrub to bloom in the spring and then once that brilliant display fades and the leaves start to appear, it’s time to prune.
The reason you don’t want to prune too late after the leaves come out and the flowers die off is because next year’s flowers grow on this year’s wood. Mine blooms in April or early May, so I try to prune soon after the leaves come out, before July. The earlier you prune, the easier it will be to discern the cuts you’d like to make without too much foliage getting in the way.
If you’ve planted a brand new forsythia from the nursery, wait until it’s established before pruning, usually about two to three years. You can remove the odd errant branch, if necessary, but the plant shouldn’t require a heavy pruning.
How do you prune forsythia?
Depending on the thickness of the branches, you could use bypass pruners if they’re thinner (this is what I use to cut branches for forcing, too), or loppers if you need to put some strength into cutting a branch with a thicker diameter. Make sure whichever tool you use is clean.
When pruning well-established shrubs that are a bit overgrown, it’s generally recommended that you prune no more than about a third. Start by looking around the shrub for the oldest stems that no longer produce leaves. These dead canes can be cut right off or to ground level. Thin out any branches that are a bit wonky and out of place.
You’ll also want to take out some of the main stems through the center of the shrub. This exposes the middle to more sunlight and airflow, helping with flower production. When pruning new canes to thin out your forsythia shrub, cut right back to where the stem comes out of an older branch, or at the base of the plant. Avoid simply cutting off the tips or parts of a branch as lateral stems will sprout from them. Consequently, that’s the only place where the new flowers will grow since they only bloom on old wood. It also results in unsightly shoots.
Rejuvenating an overgrown forsythia
If you want to really cut back an overgrown forsythia, you could try the coppicing method, which will rejuvenate it completely. Sean James explains coppicing pretty thoroughly in a video he produced, where he uses a reciprocating saw to coppice a deutzia. However, you can do this with most multi-stem deciduous shrubs, including forsythias. A hard pruning like this can be done every three to four years. And this technique can be done in late winter or early spring, while the shrub is still dormant.
Pruning a forsythia shape
Some gardeners like to prune their forsythia into a perfect sphere. Others trim so that all the branches stick up at the same length, kind of like an upside down broom. I prefer a more natural, wild look, where branches reach different lengths, with the longer ones bowing gracefully in a gentle arc and other ones standing straight up.
Earlier I mentioned a forsythia hedge. My yard came with one that divides part of my backyard from my neighbors’ property. They prune their side a little neater, like a real hedge. They’ll go in and take out some of the new shoots in the summer when it becomes unruly. My side grows a little wilder. You can use a hedge trimmer for this task. It does involve pruning the tips of branches, which I recommended against earlier. However, it’s necessary for that hedge shape. It does result in less flowers in the spring, and a more disorganized center of the shrub. But it should fill in nicely and provide privacy. You may wish to do a thorough rejuvenation every few years, which will result in a temporary lack of privacy—if that’s the reason for the hedge!