Illustration Marly Hendricks ‘When you get home, cut the stems at an angle,’ is the standard advice at the florist’s. But why, actually? ‘It is certainly important to trim flower stems before putting them in a vase,’ says Nieves García, an ornamental crops researcher at Greenhouse Horticulture. ‘They can absorb water better then.’ If the stems have not been in water, they may have sucked in air and the air bubbles in the vessels then prevent water absorption when you put the flowers in water again. The bottom of the stem has often dried out as well, and it can harbour bacteria.
So that’s three reasons to trim the stalks of your flowers. But according to García, it makes no difference whether you cut them straight or at an angle. ‘A study was done on that at FloraHolland’s ornamental plant testing centre. It doesn’t affect how long the flowers last.’ The idea behind the advice is that an angled cut exposes a bigger surface. ‘That’s true,’ says García, ‘but the water absorption rate depends on the number of xylem vessels and the connections between them, and that is no different.’
Cutting stems at an angle makes no difference to how long the flowers last
Nieves García, an ornamental crops researcher at Greenhouse Horticulture
She does have another argument for cutting at an angle, however. ‘It’s harder than cutting straight, so you need a good sharp knife. That will give a nice clean cut and you won’t damage the stem as much. And that is important because when the stem is damaged, sugars can leak into the water and stimulate the growth of bacteria.’ So it doesn’t matter whether you cut your flower stems straight or at an angle as long as you use a sharp knife.
García has another couple of tips for making your flowers last longer. ‘Make sure the vase and the water are really clean: bacteria are your bouquet’s biggest enemy. Dissolve the little packets of flower food thoroughly and at the right dosage. It’s best to put cold water in the vase. Tepid or warm water is sometimes advised, but research has shown that after being left out of water, flowers absorb cold water the fastest: the air that got into the stalks when they were dry has to dissolve in the water so it no longer blocks the way. More air dissolves in cold water than in hot water, although after that the water temperature turns out to have very little effect on the lifespan of a bunch of flowers.’
Every day we are bombarded with sometimes contradictory information. So what are the facts of the matter? In this feature, a scientist answers your burning questions. Asking questions makes you wiser. Do you dare ask yours? Email us at redactie@resource.nl
Uulke always said that because if you cut them straight, putting them on a cutting board with a ordinary kitchen knife, you squeeze the xylem vessels, inhibiting the water uptake. The advise to cut them in an angle comes from that; if you cut them in an angle, you cant squeeze the xylem vessels. Also, never use warm water indeed, best is to put a few ice cubes in the vase.