Why some cut flowers last far longer than others

Vase life is largely decided before you ever reach for the snips. Thick, waxy petals lose moisture slowly; thin, papery ones collapse in a day. The width of a stem's water-carrying vessels matters too, as does how quickly a plant produces ethylene, the gas that triggers ageing. Some genera, such as alstroemeria and chrysanthemum, are simply built to hold their condition for a fortnight or more. Others, like poppies and sweet peas, are wonderful for a day or two and hopeless beyond that.

The practical lesson is this: if you want arrangements that still look good on Thursday or Friday, grow varieties with cutting performance bred into them, not just ones that look lovely on the plant. Seed packets and catalogues usually mention vase life, and it pays to read that line as carefully as the flower colour.

The dependable performers

These are the stalwarts of a British cutting patch — tough, generous and reliably long-lasting in water.

• Alstroemeria — two weeks or more. The Peruvian lily is the undisputed champion of the vase, and modern border types are hardy enough to overwinter in most of the UK.
• Chrysanthemums — spray types last two to three weeks. Underrated by gardeners and adored by florists for good reason.
• Carnations and pinks — up to a fortnight, and they tolerate being crammed into a vase with other stems.
• Zinnias — seven to ten days in clean water. Choose tall, large-flowered types such as 'Benary's Giant' rather than dwarf bedding varieties.
• Dahlias — five to eight days, but they are worth every one of them. Darker, thicker-petalled varieties generally outlast pale, single ones.
• Antirrhinums (snapdragons) — seven to ten days, and they carry on opening up the spike.
• Larkspur and annual delphiniums — a week to ten days, and the blue tones are hard to find elsewhere.
• Gladiolus — a week or more, especially if you cut with only the bottom few florets open.
• Rudbeckia, echinacea and scabious — seven to ten days. These daisy-form flowers give late-summer arrangements their backbone.
• Hylotelephium (sedum) and Hydrangea paniculata — both excellent, provided you condition them properly.
• Alliums and gypsophila — a fortnight and a week respectively, and both are useful for filling out an arrangement cheaply.

Beautiful but brief — grow them anyway

Some of the best-loved cutting flowers are hopeless travellers. Sweet peas rarely manage more than four or five days, tulips keep growing in the vase and often lean, and poppies, nigella, calendula, cornflowers and bearded iris are best measured in hours rather than days.

This is not a reason to leave them out. It is a reason to plan for them. Use short-lived flowers in small posies for the kitchen table, cut them in the cool of the evening, and keep them away from the front of a sunny window. For arrangements meant as gifts or for a special occasion, lean on the long-lasting list instead.

Cut at the right moment

However good the variety, poor timing will halve its vase life. Go out early in the morning, before the heat builds, with a clean bucket of cool water and sharp, clean secateurs. Cut on a slant so the stem does not sit flat against the bottom of the bucket.

• Cut spike flowers such as snapdragons and gladioli when the lowest two or three florets are open.
• Cut dahlias, zinnias and sunflowers when they are fully open and the stem feels stiff, not when the bud is still tight.
• Cut chrysanthemums when the outer petals have just unfurled.
• Cut hydrangeas in the morning after a cool night, or after rain, and never in the heat of the afternoon.

Drop each stem straight into the bucket as you go. Even ten minutes lying on a warm path makes a measurable difference.

Conditioning is where the extra days come from

Once indoors, strip all leaves that would sit below the waterline — submerged foliage rots and clouds the water within a day. Re-cut each stem at an angle under running water if you can, then stand the bucket somewhere cool, dark and draughty-free for at least four hours, ideally overnight.

A few stems need special treatment. Milky-sapped flowers such as poppies and euphorbias should have their stem ends dipped in boiling water for ten seconds, or briefly seared with a flame, to seal the sap and stop it blocking the vessels. Woody stems, including hydrangea and flowering shrubs, benefit from a vertical slit up the base of the stem with a sharp knife.

Keep buckets well away from bowls of ripening fruit. The ethylene given off by bananas and apples will shorten vase life dramatically.

Keeping the vase fresh through the week

Good aftercare is simple but relentless. Wash vases in hot soapy water between uses, because bacteria left on the glass will shorten the life of the next bunch.

• Change the water every two days, and re-cut the stems by a centimetre each time.
• Use a proprietary flower food, or make your own: a teaspoon of sugar and a few drops of thin bleach per litre of lukewarm water.
• Keep arrangements out of direct sun, away from radiators and off the top of the television.
• Remove fading blooms promptly — one decaying stem can sour the whole vase.

Do those four things and a well-chosen bunch of British-grown zinnias, dahlias and chrysanthemums will comfortably take you from Sunday evening to the following weekend, still worth showing off.