Which flowers should you be cutting in your garden?

Some flowers won’t last as long if you don’t cut them regularly. We hear from an expert.

By Helen McGurk
Friday, 10th June 2022, 3:53 pm
A basket of cut flowers.
A basket of cut flowers.

Worried that cutting flowers from you garden to enjoy indoors, may halt your outdoor blooms? Well, that rather depends on the plants. There are some flowers which rely on you cutting them during summer to give you a longer blooming season, says Leigh Hunt, RHS principal horticulturist.

“Annual plants have one purpose in life – to flower and set seed, which they need to do before they die. They are in a rush to do it because if they don’t set seed, they won’t produce the offspring that are going to continue the next generation of plants. It’s like a survival instinct.”

Cutting these plants triggers “a hormonal response, which tells the plant it hasn’t managed to set seed and therefore it needs to grow more flowers,” explains Hunt. “As long as we keep the plants well watered so they have the resources, they will produce more blooms.

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“Heat in one sense speeds up the maturation time of the seeds, and if the plant gets dry, it will rush to make seed and stop putting its energy into flowering.”

There’s are some of the best garden flowers for cutting…

1. Sweet peas

These fragrant climbing favourites need cutting regularly before they set seed and produce pods, which look like mangetout. “You can often get sweet pea blooms from June to September if you keep picking them,” Hunt notes. “Also, keep the soil damp but not soggy to keep them going.”

If you don’t cut the flowers, it signals to the plant that the cycle is nearly over and they will die back quite early, as the pods form with the seeds inside, he explains. “Not picking them will shorten the life of the plant and the length of the display.”

If you forget to cut them and see pods forming, it will set them back. But if you remove the pods and the flowers they should start to generate more blooms, Hunt says. “Leave it too long and they will start to die off weeks earlier than they would have done.”

2. Cosmos

These pretty daisy-like annuals with delicate wispy foliage will produce more blooms when you cut them.

“You can get pink, white, red and even yellow ones now, and they produce masses of yellow-centred flowers,” says Hunt. “You can get double ones too, offering a real mix of colour. They can be sown directly into the ground at this time and will grow quite readily.”

3. Rudbeckia

“These are again daisy plants, which have apricot, marmalade and yellow colours, which will go on flowering once you’ve cut them,” adds Hunt.

“Rudbeckia love the heat and will thrive in warm conditions. There are some perennials, such as Rudbeckia ‘Goldsturm’, which may not give that continuity of blooms when cut but will return year after year.”

4. Dahlias

“They are bought as tubers, and are perennials, but you often grow them like annuals, planting them out at the end of May because they are tender,” says Hunt. “They will produce more flowers as you cut them.”

5. Chinese asters

“You can get a really bright mix of colours of these flowers, pinks, purples, lemons and whites. They have big pom-pom daisy-like flowers, which will bloom into September,” Hunt says of these pretty picks. “They give later season colour, and while the first blooms are the best for cutting, you do get smaller secondary flushes into autumn.”