6 Plants to Prune in September, According to Experts

This month may feel like a 30-day goodbye to summer, but that doesn’t mean you should neglect your garden, especially when it comes to trimming and pruning plants ready for the fall days ahead. So say hello to the plants you should prune in September.

From pruning roses and lavender to learning how to properly cut spent flowers off plants, it’s important to get to work with your pruners when a plant’s time has passed and it’s ready for its next season.

That is why, if you want your outdoor space to remain beautiful, you must establish a pruning and maintenance schedule, taking care of the plants that you avoid pruning in summer. In fact, September is one of those months that you will have to pay special attention to, since there are a good number of plants that will need to be pruned before the colder days arrive…

5 plants to prune in September

We imagine that, like most proud gardeners, you’ve probably filled your little oasis with the best garden plants possible – and are feeling a little… well, a little… sad It’s time to prune them now that summer is coming to an end. However, pruning is still the best way to a) stimulate their growth and b) keep them in perfect condition.

“In the UK, September is a great time to prune back certain plants and shrubs as the growing season slows,” says Christopher O’Donoghue, co-director of Gardens Revived, who adds that it’s his favourite way to prepare his plants for winter.

“Whatever plant you are pruning, always make sure to use clean, sharp tools to avoid the spread of disease,” he adds.

Christopher O’Donoghue

With nearly two decades of experience as a professional gardener, Christopher established Gardens Revived with his brother, Andrew, in 2018 to create a thriving family business. Together they have worked on residential gardens, sites of historic interest, large estates of over 70 acres and award-winning show gardens.

With that in mind, here are 5 key plants you should prune in September…

1. Lavender

close-up photo of a lavender plant in the garden to support a guide on what plants to prune in September

(Photo credit: Getty Images | Jacky Parker Photography)

If you’re lucky enough to have a garden filled with the sweet scent of purple lavender, it’s important to know how to care for a lavender plant, including putting it on your list of plants to prune in September (or whenever the flowers start to fade).

“Prun it back into a compact shape, but be sure to leave some new growth on each stem – lavender often won’t regrow from bare wood,” advises Monty Don via his popular gardening blog.

“These new shoots will grow quickly and provide an attractive, healthy cover to protect the plant in winter and serve as a foundation for next year’s display.”

2. Perennial herbaceous plants

garden with Hosta plant

Garden with hostas and other herbaceous perennials

(Photo credit: Getty Images | Mkovalevskaya)

From delphiniums to geraniums to hostas, Christopher counts herbaceous perennials among the plants to prune in September.

“You’ll need to cut back dead or dying foliage and stems, and put them away when they start to die back for the winter,” he explains.

Don’t be afraid to prune these plants hard, cutting them back to the ground if necessary – the key, after all, is to preserve the crown (base of the plant), which will remain dormant over the winter, ready to produce new shoots in the spring.

“You can, however, leave the ones with decorative seed heads in place for wildlife to enjoy,” Christopher adds.

3. Shrub roses

Close-up of a pink rose bush

(Photo credit: Getty Images | Feifei Cui-Paoluzzo)

One of the most attractive plants around, Christopher says September is the best time to tidy up your shrub roses and encourage them to focus on strong, healthy growth for next season.

However, while he suggests “light pruning and removing spent flowers”, Monty Don says you should “not worry about the position or angle of the cuts, but cut back any long, straggly shoots as if you were trimming a hedge, leaving a compact, slightly domed bush that is about two-thirds of its original size”.

4. Summer raspberries

close-up of a raspberry bush to support a guide on plants to prune in September

(Photo credit: Getty Images | Mike Powles)

Anyone who’s started growing vegetables for beginners has probably branched out (ha!) into fruits at some point as well – and raspberries, being among the easiest to grow, are usually at the top of most people’s “grow your own” list.

But the problem is that summer raspberries are one of the plants you should prune in September (along with other soft, bushy fruits like blackcurrants, gooseberries and redcurrants).

“Cut back the old fruiting canes that have fruited this year, leaving the new ones to develop for next year’s crop,” advises Christopher, who says this is the best way to encourage next year’s fruit. And keep the plant healthy.

It’s then a good idea to tie the remaining canes to a support, like this MRGARDEN raspberry trellis and this MRGARDEN grapevine stake trellis from Amazon.

5. Yew hedges

garden with yew hedges which are among the plants to be pruned in September

(Photo credit: Getty Images | mtreasure)

According to the RHS, a yew hedge can grow vigorously, up to 30cm per year. To this end, it is essential to prune it at least once a year, and early autumn is the ideal time to do this if you want it to look fresh and neat for the colder months ahead.

“The idea is to trim the hedge one last time before winter,” Christopher explains. “The aim is to maintain the shape of the hedge and prevent it from becoming too tall before the dormant season.”

Make sure to check your hedge before starting work and wait if you find an active nest (disturbing nesting birds is a criminal offence). And, of course, don’t forget to wear protective gloves when gardening, as yew is highly toxic.

We recommend purchasing a pair of WESTWOOD FOX gardening gloves on Amazon.

6. Jasmine

White garden gates with flowering jasmine climbing plants

(Photo credit: Getty Images | Chris Hackett)

Like deciduous honeysuckles and passion flowers, jasmine is one of those climbing plants that you should prune in September, ideally just after they have finished flowering.

As well as thinning out crowded or damaged shoots, the RHS advises ‘cutting flowering stems back to a strong side shoot further down’ to give new growth time to mature and flower early next season.

FAQ

Which plants need pruning in September?

If you want to know which plants need pruning in September, point your pruning shears at the following:

Lavender and other Mediterranean shrubs (like rosemary)
Yews and other evergreen hedges (cypress, box, etc.)
Raspberries and other soft or bushy fruits (blackcurrants, redcurrants, etc.)
Shrub roses
Herbaceous perennials (such as delphiniums, geraniums, and hostas)
Jasmine, common honeysuckle and passion flower

“It’s important not to prune too late in the autumn, as the new growth stimulated by pruning may not have time to harden off before the first frost,” advises Christopher O’Donoghue of Gardens Revived.

Is it possible to trim hedges in September?

If you’re wondering whether it’s okay to trim hedges in September, there are two things to consider: are there signs of bird nesting and what type of hedge is it?

Of course, it is forbidden to disturb nesting birds. If you notice that your hedge has become home to a family of feathered animals, lower your scissors and wait until they have left the area.

Once this stage is established, yews and other evergreen hedges (such as cypress and box) will benefit from pruning in September and early autumn.

“Always remove any dead, diseased or damaged wood to promote plant health,” says Christopher O’Donoghue of Gardens Revived.

Now that you know which plants you need to prune in September, it’s time to get to work pruning and tidying everything up for the next big season to protect your plants from frost.

You’ll be glad you did the work when the first frosts arrive, trust us…