The tricks to keeping flower arrangements gorgeous for as long as possible

Pretty petals and vases are just the beginning—especially when it comes to fending off bacteria.

Bringing flowers home from the shop or plucking them from your garden is just the first step in keeping them fresh and lovely in your home. But taking care of a floral arrangement is more than just filling up a pretty bowl with water. You’ve got to care for your plants by protecting them from bacterial growth and wilting through a step called conditioning.

Luckily, you don’t need to be an expert florist to make your bouquets last as long as possible—and in some cases, all you’ll need is a cotton ball or a teaspoon of sugar.

Cultivated: The Elements of Floral Style, out next week, provides the perfect guide to arranging and maintaining your blooms, and some gorgeous photos for inspiration.

The following is an excerpt adapted from Cultivated: The Elements of Floral Style by Christin Geall.

Conditioning Flowers

The professional term for postharvest care of flowers is conditioning. In commercial applications, conditioning usually involves a clean cut once the flowers have come in from the field and a resting period in water to which a chemical hydrator and/or a nutrient-based product have been added to encourage flower development. Often an antibacterial agent is used, as well.

The principles of conditioning are important to understand, whether you grow your own flowers or purchase them. If your flowers have been conditioned properly, they won’t wilt when you bring them indoors, nor be half as thirsty in the vase. However, every type of flower has unique tastes and predilections, so I’ll start with some basic principles and get more specific as we go.

Clean water is of the utmost importance. Tepid is better than cold.

Cover of Cultivated
Cultivated is out on March 24, 2020. Princeton Architectural Press

When you come home from the shop or in from the garden, strip the lower leaves from stems. Leaves continue to transpire (give off water vapor) after a flower has been cut, so keep only those necessary to your work. In some cases, such as with lilacs, it’s best to remove them all.

Different types of flower stems should be treated differently at this stage. The British Florist Association has a handy guide online covering hearty stems, hollow stems, woody ones, milky ones, and so on. Generally speaking, hollow stems (such of those of delphiniums) should be filled with water and plugged using a cotton ball and an elastic. Lupines and amaryllises also have hollow stems and heavy heads, so it’s wise to support the flower with a prop. Floral maven Sarah Raven recommends using bamboo cane (I’ve used barbecue skewers too), as an insert. Fill the stem with water, place the support inside, trim it to length, and then stuff cotton wool into the hole. Wrap an elastic around the base to hold the whole thing together. Although this might seem tiresome, you’ll be thankful you did it.

If you are using woody stems, slit them, score them with an x, or smash them with a hammer at their base to allow the stems to absorb more water. Shrubs, blossoming branches, chrysanthemums, and roses all qualify as woody.

The stems of spring bulbs like tulips and hyacinths may have a white portion that doesn’t absorb water, so trim this off. Narcissi (daffodils) exude a slimy sap after cutting. Change the water repeatedly before arranging.

Many soft-stemmed plants benefit from a hot-water dip. This method damages the cell walls of stems and allows the cut flower to take up water. Dip about 10 percent of the stem length for about twenty seconds in freshly boiled water, being careful not to steam yourself or the flower. I keep an electric kettle in my studio for opium poppies, Cerinthe, and euphorbias. You can try this method with wilted roses, too, adding a teaspoon of sugar to the water they rest in after searing. In a few hours, they may revive.

Another method for quickly treating sappy stems is to burn them. This damages the stem so it can absorb water and also seals it off, preventing wilting. If I have a small number of Icelandic poppies, I’ll simply sear the stems with a barbecue lighter. Flower farmers use propane blowtorches. Just run the flame along the lower portion of the stem until it goes semi-transparent and the sap bubbles and burns a bit at the cut end of the stem.

Foliage can be revived just as you might lettuce for a salad. Place the leaves in a cool bath, then shake off excess water and store them at a low temperature to perk.

After whatever special treatment you’ve doled out (the requirements of each type of flower can be a bit intimidating, but you learn them over time), leave your flowers to rest in deep water, in a cool place away from direct sunlight. Try to leave them for a few hours or overnight before arranging.

Carefully top up your vessel with water after arranging; use a small watering can for fitting in between stems.

Remember to keep your arrangement away from sun and heat.

Keeping Flowers Fresh

Every living thing carries a microbiome, flowers included. In vase water, bacteria propagate, feeding off their primary food source—the cut ends of stems. The stems degrade eventually (giving old vase water that special swampy stench), but before that point the bacteria clog your plant’s stem capillaries, preventing them from taking up water and shortening the vase life of your flowers. This is why freshly cutting stems is often recommended to prolong the life of flowers.

I religiously change water daily and advise my customers to do the same. If the water can’t be poured out easily, just run fresh water into the flowers to flush.

Additives can also help. Sarah Raven advises, “What cut flowers need is a balance of sugars that can be utilized for metabolism, a substance to raise the acidity of the water and an antibacterial agent. Commercial sachets of cut-flower food contain agents for all three.”

If you don’t have “flower powder” or if you eschew plastic packages or those mysterious substances known as “agents,” you can, as Raven suggests, improvise with a teaspoon of sugar and a couple drops of bleach. I’ve also heard vodka can work to slow the growth of bacteria.

If I seem reluctant to advocate specific products or potions, it’s because each type of flower has its own response to various substances (astilbes, aye to alcohol; Asclepias, yea to sugar), and the level of detail involved in itemizing who loves what could crush your enthusiasm. If, however, you’re one of those conscientious people who like to be armed with all the facts, seek out “Conditioning Flowers,” a wonderful flower-by-flower online list of management and care compiled by the garden club of Brookfield, Connecticut. Sarah Raven also offers detailed advice in her now-classic 1996 book “The Cutting Garden”. I highly recommend it.

Excerpted from Cultivated by Christin Geall, published by Princeton Architectural Press. Reprinted with permission. All other rights reserved.