Pruning forsythia

Pruning forsythia is not essential for its healthy growth, but it helps maintain a bushy habit with an attractive and aesthetic shape, vigour and good floriferousness in early spring. To achieve this, maintenance pruning should be carried out at the right time to avoid hindering the flowering of this deciduous spring-flowering bush. Moreover, pruning methods vary depending on the bush's maturity and history. Indeed, an ornamental bush left unattended for many years requires rejuvenation pruning to rebalance its silhouette and renew its branching. Discover all our tips for successfully pruning forsythia and enjoying its dazzling yellow flowering!

Forsythias with a natural silhouette

When to prune forsythia?

Pruning forsythia is not obligatory but recommended to maintain a well-balanced silhouette. Annual maintenance pruning helps keep your forsythia's habit homogeneous and limits its spread.

Prune forsythia within 1 to 2 months after flowering ends, i.e., from May until mid-June. Before winter, forsythia forms flower buds on the current year's wood. The buds open the following spring, revealing a multitude of yellow flowers. If winter pruning is done in winter, much of the flowering will be lost. Additionally, if pruning is done too late in summer (July/August), the bush won't have time to produce new shoots bearing flower buds before winter. The following year's flowering will then be almost non-existent.

How to prune forsythia?

Required tools

To prune forsythia, equip yourself with the following tools:

A secateurs
A pruning saw (e.g., a Japanese curved-blade saw)
A lopper (also called long-handled pruners or branch cutters)
A pair of gloves

Check the condition of your pruning tools. Sharpen and disinfect them properly to ensure clean cuts, promote good wound healing, and reduce the risk of infection to your forsythia.

Additional details

For a young plant about to be newly planted, lightly trim the aerial parts. Remove dead and weak branches. Shorten diseased or broken branches above the damaged area. The remaining stems are shortened by one-third.

Allow your flowering bush to grow freely for the first two years after planting. If needed, simply refresh dead, thin, or tangled stems. Maintenance pruning can begin from the 3rd year.

Nursery-grown bushes are usually already shaped and have between 5 and 10 main branches. Thus, no formative pruning is required.

Maintenance pruning

First, remove diseased or broken branches, as well as dead wood.
Cut back all the flowering shoots that are too long. Reduce by one-third those that have just flowered and are of moderate size. To do this, cut the shoots 5 mm/1 cm above a bud (or eye), at an angle on the side opposite the bud. This prevents rainwater from stagnating on the pruning wound and flowing onto the bud.
Eliminate thin branches, which are too weak, by cutting them at the base.
To allow light to penetrate the centre of the stump, thin out the heart of the forsythia by removing branches that cross through the bush's branches and intersect with others. Note that these branches can cause wounds through rubbing.
Remove trailing branches that are too close to the ground.
Finally, dig up suckers that have formed at the base of the bush, as they can unnecessarily drain its energy.

Once pruning is complete, the bush's silhouette should be harmonious and regular, with well-distributed branches.

Left: a forsythia with many tangled shoots producing few flowers. Right: a forsythia with abundant flowering thanks to proper pruning.

When to prune an old forsythia?

After a few years (from 4 years onwards), forsythia tends to flower less. If neglected, it loses its beautiful silhouette by growing too tall and becomes bare at the base. Additionally, it becomes more susceptible to diseases. Cutting it back will stimulate new shoots, thus rejuvenating it. This radical pruning allows it to regain a more compact and aesthetic shape, as well as more abundant flowering.

Rejuvenation pruning (or coppicing) can be done when your plant becomes too large and unsightly, every four to five years and always after flowering. This way, new branches have time to form and strengthen before winter. The forsythia may flower less the following spring, but it will recover the year after. Some regions of France may experience intense spring heat, so avoid pruning on hot days.

How to rejuvenate an old forsythia?

Cutting back involves severely shortening the main structural branches. Forsythia tolerates this drastic pruning close to the ground very well. After this pruning, the bush will produce vigorous new shoots at its base (brown in colour), thanks to the many dormant buds under the bark that will sprout.

Rejuvenation pruning

Use the appropriate cutting tool (lopper or pruning saw) depending on the branch diameter. As with maintenance pruning, always cut at an angle.

For a plant aged four/five years, cut back all the bush's shoots to about 30-40 cm from the ground.
For a forsythia over five years old, cut approximately two-thirds of the oldest wood at the heart of the bush (thick grey branches) close to the stump. When pruning, ensure you don't injure the remaining shoots with your tool. The main branches left above the ground will act as "sap drawers," stimulating sap circulation and the regrowth of new stems.

forsythia branching, rejuvenate forsythia

Pruning stimulates new shoot growth at the base of the bush (photo sk - Flickr)

Alternative method: gentle pruning

A less radical approach spread over 3 years is possible. Each year, remove up to one-third of the oldest branches. This allows the bush to regenerate gradually without depriving us of flowers and foliage, unlike a fully cut-back forsythia.