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How to Keep Cut Flowers Looking Fresh, With Science

Want to keep your blooms bright and stems stiff? Here are some science-based ways to preserve cut flowers – a penny in the vase not included.

It's a lovely feeling to wake up in the morning and be greeted by a beautiful bouquet artfully arranged in a vase. But it's a far less pleasant one when you start to notice their petals falling, leaves wilting and stems drooping. Drawing on some knowledge of chemistry and biology, here are a few things you can do to prolong the life of cut flowers using nothing outside what's likely already in your home.

Cut the stems

You’ve likely seen someone snipping off the tips of flower stems and carefully organizing them into a receptacle before but allow me to explain the logic behind these actions.

By varying the heights of stems, you’ll help avoid excessive crowding around blooms. This has the dual purpose of preventing flowers from physically bumping into one another and having their petals knocked off and lessening the opportunity for microbial growth in dense wet clumps of foliage.

If you’ve ever placed some floppy celery in a glass of water and watched it magically turn crunchy again, you’ll intuitively understand that plants rely on turgor pressure to stay rigid, even if you’ve never heard that term. Turgor pressure, or hydrostatic pressure, is the force within plant cells that pushes their plasma membranes up against their cell walls. If plants can’t suck in enough water, their hydrostatic pressures fall, and you get wilting, floppy stems, leaves, and petals.

By making fresh cuts to step tips, you open a channel for water to enter and keep your bouquets looking crisp. By cutting at an angle, you can help avoid air bubbles in the stems that can block the flow of water. Latex-emitting plants (like poinsettias, heliotropes, or poppies) can become plugged with sap, preventing water intake. This can be avoided by heating their stem tips briefly, either with a flame or by dipping them in boiling water. While you’re trimming, remove any lower leaves that would fall below the waterline of your vase. These can rot and promote bacterial growth that can lead to plugged stems. It’s also a good idea to sterilize, or at least wash, your scissors and vase before use, to minimize potential microbial contamination.

Use plant food

You may wonder what the point of the little sachet of plant food enclosed in your purchased bouquet is really for. It generally serves three purposes – acidifying the water, providing a source of carbohydrates, and preventing bacterial growth. A slightly lower pH can increase the amount of water that a cut flower takes up, helping to maintain turgor pressure. It also helps inhibit the growth of bacteria, fungi and other microorganisms that can rot, clog, and generally degrade your blooms. Most commercial plant foods contain further agents to limit the growth of microbes, such as silver or chlorine compounds.

Being a food source for your flowers is where plant food gets its name and is perhaps the most important function it performs. Maintaining a life-like look in cut flowers relies in part on maintaining their metabolic activities, which are powered by carbohydrates, just like ours. Sugars can also help plants retain moisture and not dry out.

If you don’t have any of the typically-freely-enclosed plant food, you can make your own at home quite simply. There are a variety of recipes, but they all include a source of sugar, something acidic, and a substance to limit microbial growth (typically bleach).

Minimize stress

No one is happy when they’re stressed, and plants are no different. To preserve your flowers, you’ll want to keep them in the most peaceful conditions you can. This means minimizing direct sunlight and heat that will dry them out, cause vase water to evaporate, and increase their metabolic rates. There’s a reason florists store flowers in fridges, and you can imitate them if you’re really motivated to preserve your bouquet.

Importantly though, don’t store your flowers next to fruit! Ripening fruits, especially bananas, tomatoes, and avocados, give off ethylene gas. It’s a plant hormone that increases many of their natural processes, including senescence, aka dying. Some species like carnations, daffodils, delphinium and lilies are especially sensitive to ethylene. Keep your blooms away from your fruit basket, but also from external sources of ethylene like car exhaust, cigarette smoke and other decaying plants. It may seem cruel, but removing any flowers that are starting to die can help preserve the remaining ones.

You'll also do well to minimize any physical movement of flowers, as this can increase their rates of petal drop and ethylene production. That means avoiding strong breezes, not moving vases around too often, and keeping them away from vibration sources like tumble dryers.

If all else fails

No one likes to see wilting, dying flowers. But if you remove them at the first signs of decay and hang them upside down to dry, you can create lovely, preserved blossoms that last nearly infinitely longer. My home is personally adorned with many dried bouquets of blooms – beautiful memories of gifts that don't require water or any special care. And I’m planning on making some dried flower garlands to hang up soon!

You may also consider choosing flowers known for their longer vase-lives in the future. Dahlias, irises and daffodils are lovely but known for typically lasting less than 5 days once cut. Gravitate towards carnations, tulips, chrysanthemums and anthuriums to enjoy your bouquets for two weeks or longer.


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