Pruning forsythia: when and how to do it the right way

If you follow our advice on pruning forsythia, it will make all the difference to how it looks. Despite its many virtues – fast growing, tough, easy-to-cultivate – forsythia seems to suffer from a major image problem. Some see it as old fashioned while others simply hate it. One of the reasons for this is the way it’s often hacked at during pruning, which can leave it looking much the worse.

As forsythia grows fast, reaching maturity in under a decade, wayward growth can leave it looking messy. This often leads to it being butchered with the shears. If planted in the wrong place it can rapidly outgrow the space and this leads to another bout of hacking to try to tame it. But being vigorous by nature, it will simply respond by growing even more enthusiastically.

If your forsythia is correctly pruned it can be a real asset to the garden. Flowering in early spring they bring the garden alive with a burst of sunshiny yellow. The key thing to remember is to prune it after your shrub has finished flowering. Once the flowers are over the plant steps out of the limelight until the following spring when those golden yellow flowers appear once more to add their unique splash of color.

Top tips on pruning forsythia for great results 

When it comes to pruning shrubs, it's worth remembering that forsythia are vigorous growers. With maturity reached so quickly getting the right pruning regime in place is vital, and fortunately it’s really straightforward. Once established all they need is the correct pruning to encourage flowering in spring time. 

'It is important to learn how to prune forsythia at the right time – immediately after flowering,' says Amateur Gardening's expert Graham Rice. 'All the shoots that develop during the rest of the year after pruning should develop flower buds for the following season.

'As a general guide, look carefully at the forsythia branches that have just finished flowering. You should see pairs of buds all along each shoot. Count three or four buds from the base, grab your pruners and snip. Do this over the whole plant.

'If you need a quicker option for pruning forsythia to get it into shape, never fear – you can use your best hedge trimmer for a more rough and ready approach. The aim should be to remove the same amount of growth. Do not worry about being too precise. It works well.'

Pruning a new forsythia

For the first two to three years after planting a new forsythia don’t prune it. This lets the bush develop into an attractive natural shape and helps establish a good root system.

When your shrub is three or four years old it’s time to start pruning forsythia. The timing is easy – always do it after flowering. It’s important to prune then as forsythia flower on shoots grown the year before flowering, so if you prune too late you’ll be removing the flowers for next year. You can shape it by removing about a quarter of the length from all stems.

Every other year, prune about a quarter of all stems back to ground level from the center of the bush. When doing the above keep an eye out for damaged stems. Trim these first, then move on to dealing with any stems which are crossing over each other.

After five or six years it’s a good idea to remove about 20-30% of the oldest stems completely, right down hard to the ground. This will stop the bush from becoming congested and improve air circulation, reducing the risk of disease.

Pruning an established forsythia

If you inherit a very overgrown forsythia bush that’s not in the best shape and needs smartening up, the best plan is to chop it back completely to a height of around 3ft (1m) once the flowers fade. It will produce very few flowers the next year but will soon recover by the year after. 

Although an established forsythia can be hard pruned virtually to the ground, if you want to maximize flowering it's best to remember to prune them once a year.

Need the right tools for the job? You'll find what you need in our guide to the best loppers. 

What can I do if my forsythia has got too big?

If after a few years of planting, your forsythia starts to dominate and become huge, what should you do? Well, it sounds as if this is more of a case of what you didn’t do! 'Forsythias that are not pruned soon become larger and larger, and eventually outgrow their space,' explains Graham Rice. 'Regularly pruning forsythia immediately after flowering not only encourages more flowers but keeps the plant to a manageable size.'

You can remedy the situation by grabbing your best secateurs and taking action. 'Immediately after flowering, you need to cut the whole plant back to around 2-3ft (70-90cm) in spring,' adds Graham. 'You may lose a year of flowers – but if you then prune every year, you will restore your forsythia back to a more colorful and manageable plant.'

Does forsythia make a good hedge if pruned?

Forsythia is a popular choice for hedges, but it doesn’t make a neat hedge because it goes against its natural form of growth. Unlike some of the best hedging plants such as smarter yew, beech and privet, it can look unkempt between trims and pruning. It doesn't look right as a 'natural' edge either as its too dense. Plus those vivid yellow flowers can somehow look odd seen against the rigid geometry of a hedge.