Ethylene and the fruit bowl: why some flowers give up early

A hormone that travels through the air

Most plant hormones move through the plant in its sap. Ethylene is unusual because it is a gas. It is made in plant tissue, diffuses out through the surface and drifts through the surrounding air, where any other plant tissue nearby can pick it up. In a living plant it helps coordinate ripening, the ageing of petals and leaves, and the shedding of parts the plant no longer needs. A cut flower still carries the machinery to respond, which is why the air around a bouquet matters as much as the water in the vase.

The concentrations that matter are tiny, far below anything you could smell, and the effect builds with time. A sensitive flower sitting in slightly ethylene-rich air for a day or two can age as though it had lived much longer.

Where it comes from in a home

The fruit bowl is the usual culprit. Apples, pears, bananas, avocados and tomatoes all produce ethylene as they ripen, and ripening feeds on itself: the gas each fruit releases hastens its own ripening and that of its neighbours, so a bowl of ripening fruit gives off more as the days pass. It is the same effect that lets a ripe banana in a paper bag soften a hard avocado.

Plant material makes it too. Stems that have been crushed or split, leaves rotting below the waterline, mould on old foliage and flowers that are already fading all release ethylene, because wounding and decay are exactly the situations in which a plant signals that tissue is ageing. Tobacco smoke and engine exhaust carry it as well, which is why flower handlers are advised to keep exhaust fumes well away from stored stock.

Why some flowers collapse and others shrug

Sensitivity varies enormously between plant families. Researchers surveying petals across many species found three broad responses: some flowers wilt, some drop their petals or buds, and a sizeable group barely respond at all. The difference lies in how far a flower's own ageing is run by ethylene. In a sensitive flower, a small dose from outside switches on the flower's own ethylene production, which then drives the ageing from within. Once that switch has been thrown, moving the flowers somewhere cleaner rarely reverses it.

Carnations are the classic case. Exposed to ethylene, open carnations roll their petals inwards and close up, a response the trade calls sleepiness, while the buds may never open at all. A flower that would otherwise give around 14 days in a vase can look tired within a few, which is why keeping carnations away from ripening fruit is not folklore but the most useful thing a recipient can do for them.

Freesias show it differently. Their florets open one after another up the stem, and in ethylene-rich air the upper buds simply stall, leaving a couple of open flowers at the base and a row of green buds that never colour. Roses sit in the middle and vary from one variety to the next: some drop petals or open poorly after exposure, others hardly notice. At the other end, chrysanthemums, gerberas and most of the daisy family have low sensitivity, which is one reason they are so forgiving in a busy household.

Why the bouquet by the fruit bowl fades first

Put a mixed bouquet on the kitchen worktop beside a bowl of bananas and apples and it sits in a small, warm, often poorly ventilated pocket of air that is steadily being enriched with ethylene. Warmth makes things worse on both sides, because fruit ripens faster and releases more gas while flowers age faster and respond more strongly. Nothing looks wrong on the first day. The damage shows later, as carnations that never quite open, freesia buds that stop, and roses dropping petals ahead of their twins in another room.

Enclosed spaces concentrate the problem. A fridge holding fruit is one of the worst places to keep flowers overnight, because it traps the gas in a closed box. Moving a sensitive bouquet to a cooler room away from the kitchen does more for it than almost anything else you can do once it has arrived.

• Keep flowers and fruit in different rooms, or at least well apart, and give ripening bananas and apples a particularly wide berth.
• Strip any leaves that would sit below the waterline and lift out fading flowers as soon as they go over, since both give off ethylene as they decay.
• Re-cut stems with a sharp blade rather than blunt scissors, because crushed tissue is itself a source.
• Choose a cool spot out of direct sun and away from radiators, where the flowers both meet less ethylene and respond to it more slowly.
• Open a window now and then. The gas disperses readily, so a little ventilation stops it building up around the vase.

What growers and florists do about it

Commercially, ethylene is managed at every stage between the field and the shop. The first defence is temperature. Flowers are cooled quickly after harvest and kept cold in transit and storage, because cold slows both the production of ethylene and the flower's response to it. Cool rooms are kept free of ripening produce, and good hygiene clears out the rotting leaves and spent stems that would otherwise add to the load.

For the most sensitive crops, growers also use treatments that stop the flower responding. Silver thiosulphate, taken up through the stem as a short pre-treatment, has been used on carnations for decades and interferes with the flower's ability to perceive ethylene, although its silver content raises disposal concerns. A newer option, 1-MCP, is a gas that occupies the flower's ethylene receptors, so the flower cannot respond even when ethylene is present. Neither is something to try at home, and the sachet of flower food that comes with a bouquet is not an anti-ethylene treatment. What these measures do is deliver a carnation or freesia with its full life still ahead of it, and the recipient protects that life simply by keeping it away from the fruit.