5 plants to deadhead in August – trim away these spent blooms now to prolong their flowering period

There are so many plants you should deadhead in August to keep them blooming – and it’s likely that you’re already growing some of them in your garden.

Lots of plants can be cut back in August to encourage bonus flowers, but many annuals and perennials benefit from a lighter approach to keep them blooming through to the autumn months. That’s where deadheading comes into play – it’s a simple gardening technique that involves removing spent flowers to redirect the plant's energy into new flowers.

Here are a few plants to deadhead this August to keep them happily blooming away for the rest of their growing season. This list is by no means exhaustive – many plants benefit from deadheading, unless they’re self-cleaning annuals that don’t strictly need deadheading – but it’ll point you in the direction of the most popular candidates.

What you'll need

1. Sweet peas

Sweet peas are one of the most productive plants you can grow, because they have the potential to produce new flowers every day at the height of their season. By August, deadheading is a crucial sweet pea task.

‘Sweet peas need picking constantly if you want them to keep producing flowers,’ says Julian Palphramand, head of plants at British Garden Centres. ‘Once they start forming seed pods, the plant begins to wind down, so remove the pods as soon as you see them.’

Sweet peas are so delicate, a simple pair of garden snips like these Kent & Stowe Garden Life Snips from B&Q are perfect for the job.

2. Cosmos

Cosmos are adored for their ability to pump out blooms upon blooms right through the summer months. If you’re lucky, they’ll flower right through to the autumn – and they’re more likely to do that if you keep deadheading your cosmos this August.

‘Summer favourites such as cosmos benefit from regular deadheading and will produce noticeably more flowers as a result,’ says gardening expert Paul Parker from J. Parker’s. ‘Many annuals will also continue flowering well into autumn when spent blooms are removed regularly.’

If you’re looking for garden scissors with a more premium feel, the Niwaki Garden Snips are the best I’ve tried (and they make a wonderful gift!).

3. Repeat-flowering roses

Not all roses need deadheading, but repeat-flowering varieties absolutely do if you want them to keep flowering. With the right care, repeat-flowering roses can flower from spring to early autumn, when the first frosts arrive.

‘August is a good time to go over roses, as many will still have plenty of flowering time left,’ says Julian. ‘With repeat-flowering roses, remove the faded blooms back to an outward-facing bud.’

You can even use a sharp pair of bypass secateurs for the job, like these budget-friendly Spear & Jackson Razorsharp Advantage Bypass Secateurs from Amazon.

4. Dahlias

Dahlias are also prolific bloomers with the right care – and in late summer, deadheading dahlias becomes more important than ever.

‘Dahlias should be checked regularly for spent heads,’ advises Julian. ‘A simple rule with dahlias is that finished flowers tend to point downwards, whereas new buds are rounder and point upwards.’

For thicker stems on larger dinnerplate varieties, it’s wise to use a pair of bypass secateurs to deadhead your dahlias. These WOLF-Garten Bypass Secateurs, which you can buy from Amazon, are some of the best I’ve tried.

5. Petunias

It's also beneficial to deadhead petunias in August, and the technique can even revive tired plants.

‘A quick trim of leggy petunias can bring a tired container back into flower,’ says Julian.

‘When cutting old flowers, make the cut just above a strong leaf joint or side shoot,’ adds Paul from J. Parker’s. ‘This signals to the plant where to direct its energy, producing an abundance of fresh buds.’

Deadhead these plants in August to keep them flowering for the rest of the season.