Deadheading flowers to extend the season

Why deadheading pays off

Every fading flower is a plant doing sums. Once a bloom has been pollinated, its job is done, and the plant switches its resources from making petals to making seed. That is a costly business — seeds need sugars, proteins and minerals, all of which could otherwise be pumped into fresh growth and new buds. Remove the spent flower before that process gets going and you effectively stop the invoice. The plant carries on with the only strategy it knows for reproduction: make more flowers.

It is not magic, and it will not turn a shade-lover into a sun-worshipper, but on a wide range of garden plants deadheading is the cheapest extra fortnight of colour you will ever buy. On annuals that flower over a long season — cosmos, calendula, petunias — it can mean the difference between a good August and a spectacular one.

Which plants respond best

Some plants rebloom freely and reward regular attention; others flower once regardless of what you do. The reliable responders include:

• Annuals and tender perennials: cosmos, calendula, petunias, pelargoniums, verbenas, nicotiana, tagetes, lobelia.
• Repeat-flowering roses: most modern shrub and climbers, which will push out new buds within weeks.
• Dahlias: ruthless deadheading keeps them going until the first hard frost.
• Sweet peas: never let a single seed pod form, or flowering stops almost overnight.
• Long-flowering perennials: penstemons, salvias, hardy geraniums, geums, scabious, astrantia, heleniums and rudbeckias.
• Spike-formers: delphiniums and lupins, which can be cut back after the first flush for a smaller second showing in late summer.

Plants grown for a single dramatic moment — most bearded irises, peonies, alliums — gain nothing from it, so enjoy the flowers and save your energy.

How to do it properly

Use sharp, clean snips or secateurs, and take a small bucket round with you rather than dropping heads on the border, where they can harbour slugs and look scruffy. The general rule is to cut back to the next strong bud, leaf joint or side shoot rather than snipping just below the flower. Cutting into bare stem leaves a stub that dies back and can rot.

• Annuals and bedding: pinch or snip just above a pair of leaves, ideally where you can see tiny new buds forming in the leaf axils.
• Roses: cut back to a healthy outward-facing bud, ideally above a leaf with five leaflets, at a slight angle sloping away from the bud.
• Spikes (delphiniums, lupins, salvias): either remove individual faded florets from the bottom up as they pass, or take the whole spike back to a sideshoot for a second flush.
• Pelargoniums and geraniums: snap the flower stem cleanly at its base rather than cutting halfway, as stubs left behind tend to rot in damp weather.
• Dahlias: follow the stem down to the next pair of leaves and cut just above it. Check for buds first — they can be surprisingly well hidden.

Work in the morning if you can, when plants are turgid and the cut surfaces dry quickly, and never deadhead wet foliage if you can avoid it, as that is how fungal problems spread.

What to leave alone

A garden stripped of every fading flower becomes sterile, and some of the best late-season interest comes from what you resist cutting.

• Seedheads for wildlife and structure: teasels, echinops, sedums, ornamental grasses and sunflower heads, which feed birds well into winter.
• Hips and berries: leave roses that produce good hips, and berrying shrubs, alone.
• Self-sowers: poppies, aquilegias, foxgloves, nigella and calendula will seed themselves generously if you let a few pods ripen.
• Biennials and short-lived plants: once they have flowered, they are finished — save the seed or let them scatter it.
• Wildlife areas: in a meadow patch or pollinator strip, seed is food. Step back.

Making it a weekly habit

Ten minutes with a bucket once a week, from late June through to September, is enough to keep most borders performing. Go round in the same order each time so nothing gets missed, and combine it with a quick check for pests, mildewed leaves and anything that needs tying in. Deadheading works hardest alongside feeding: a high-potash tomato feed every fortnight keeps container plants and heavy-flowering bedding in condition to make all those extra buds. Water thoroughly rather than little and often, and mulch to hold moisture.

As autumn arrives, ease off. Let the last flowers on tender plants set seed if you plan to collect it, and leave the rest standing for the birds and for frost to catch. Your final tidy-up can wait until late winter or early spring, when the garden is dormant and the seedheads have done their work.

Do not forget the houseplants

The same principle applies on the windowsill. Streptocarpus and kalanchoe will keep flowering far longer if you remove each faded bloom and its stalk promptly. Hibiscus flowers last only a day or two, so pick them off as they collapse — the plant will keep producing buds from the tips. On indoor pelargoniums, snap spent heads away cleanly at the base, and keep an eye out for buds lower down the stem. Even a moth orchid benefits from having a brown, shrivelled flower trimmed back to the next node, which sometimes encourages a side spike rather than a slow decline.