When to prune forsythia

Due to the extra warm winter we've had this year, it’s been a good spring for forsythia. There are loads of yellow flowers on forsythia shrubs all around our area.

You may have noticed some bushes have many more flowers than others. Proper pruning makes all the difference. Gardeners with forsythia loaded with flowers have taken the time to correctly prune their shrubs. Unfortunately, some people never prune their forsythia, or if they do, they prune at the wrong time and end up never having any flowers at all.

The secret to having a lush display of flowers is to remember that forsythia flower buds begin development on new growth during the spring of the previous year shortly after flowering. The buds then complete their development during summer. These flowers buds open up and bloom only once in the spring. So, if you prune anytime when the plants are dormant, you end up cutting off those brand-new flower buds that grew the previous season.

Putting it another way, forsythia flower buds form on newly grown wood and are held on all winter for blossoming the following spring.

The optimum time to prune forsythia is right after the flower petals fall off.

Pruning forsythia is pretty straight forward. Start by removing the largest, coarsest stems cutting them off right at ground level. This will stimulate your shrub to send up fresh new stems that will form plenty of those flower buds we're looking for.

Additionally, remove any out of place branches that are crisscrossing inside the bush. Also take out branches that are rubbing against another branch and all diseased-looking branches.

The ideal shape for forsythias takes place when they are encouraged to grow into their natural profile, forming branches that grow upward for a distance then bend downward with dense sprays of yellow flowers, making a graceful vase-shaped shrub.

Many people try to shear forsythias to form a hedge much like we would do for yews. It usually ends with bushes that have a bare or flowerless bottom with a light sprinkling of flowers at the top. That is because all of the newly formed wood which contains the flowers buds gets sheared off. Those few flowers that do show up are the result of some new wood remaining after shearing. That being said, I do occasionally see shearing successfully done when the gardener keeps in mind the value of new branch growth.

The only exception to the “pruning after flowering” rule is to get an old overgrown, sparsely flowered forsythia back on track. In that case, prune in late winter by cutting back a quarter to a third of the oldest stems near to the ground, leaving stubs not more that 4 to 6inches long. When dealing with really old shrubs you might need a saw to cut the biggest stems.

Cutting off old stems will stimulate new stems to grow up from the stubs providing the plant with new flower bud producing wood. Forsythias are fast growers, so it won’t take long for them to grow back to full size after being cut back. By the second year those new stems will be producing loads of flowers.

Each year continue cutting back a quarter of the oldest stems to the ground. In subsequent years you can choose to leave longer stumps at various lengths, that will result in a more natural shape. In a year or two you'll have a more balanced looking shrub with such a dense profusion of yellow forsythia blossoms that your neighbors will think you are a gardening genius. You’ll have the handsomest forsythia on the block!