The science of keeping your Valentine flowers fresh

Sugar and alcohol

Hey — that’s what a lot of us humans will be consuming on Valentine’s Day: sugar and alcohol.

Anyway, a paper published in 2013 in The International Journal of Biotechnology and Molecular Biology Research reveals that sugar and alcohol may be the key to keeping roses fresh in the vase the longest.

This and other studies have found that cut flowers need sugar for food, clean water with a low (acidic) pH, an antimicrobial agent to keep the sugar from feeding any bad microbes in the water (perhaps the No. 1 enemy of cut flowers) — and maybe a little vodka.

Yes, vodka. (Funny how there always seems to be a bottle or three sitting around these labs.) Now, it has long been known that adding a few drops of vodka to the vase water would prolong cut flower life. Researchers originally thought that this was because the alcohol in the vodka was inhibiting the growth of those nasty little microbes (that clog up the stems and make it hard for the cut flowers to take up more liquid).

But it’s now felt that the vodka instead prevents the release of ethylene gas from the aging flowers. This natural ripening agent — famously produced by fruits such as tomatoes and bananas — shortens the life of the cut flowers by artificially aging them faster. A little bit of vodka (just a few drops in the vase water) will stop this ripening action and help the flowers last longer.

Mitigate those microbes! Feed those flowers!

Believe it or not, there’s quite a bit of published research out there on cut flower preservatives, and almost all of them have several things in common.

  • Microbial growth may be the number-one enemy of cut flowers, so starting out with a squeaky clean vase and distilled water (or filtered or spring water — just not straight tap water) is a great start, especially if you add a few drops of vinegar to keep any tiny beasties at bay.
  • Although cut, these flowers still need food, which sugar supplies perfectly. Combining and averaging the recommendations from several different papers, we’re going to recommend a 3 percent solution for cut roses — that’s 6 level teaspoons of sugar dissolved in 1 quart of lukewarm to warm water.*
  • You also need to keep the vase water acidic (low pH), so add a crushed-up vitamin C tablet (around 500 milligrams) to the warm water.
  • Re-cut the bottoms of the stems, remove any leaves that would go below the water line and place the flowers in the water while it’s still warm, but then immediately move them to the coolest spot in the house for display.

* Don’t add any sugar to cut tulip water.

Acid rock in a soda can

Most published studies agree that cut flowers need a squeaky clean vase. Washing the inside of the vase with white vinegar will give you a great start.

Then both the University of Florida and University of Minnesota Extension suggest you provide the sugary food and low pH in one shot by mixing one can of nondiet 7UP or Sprite with three cans of water; add a few drops of vinegar and use that mixture for your vase water.

Oh, the University of Florida researchers also tested some folk remedies, and they say to forget about dropping a penny in the water to kill bacteria. Yes, they explain, copper is a very potent antifungal, but the copper in a penny isn’t soluble in water.

So, to sum up:

  • Mix one can of nondiet 7UP or Sprite and three cans of distilled or purified water to make a solution that provides needed sugar and acidity.
  • Add a few drops of Vodka to counteract any release of ethylene gas.
  • Add a few drops of vinegar for the needed antifungal.
  • Use a clean vase.
  • Remove any leaves that might go below the water line.
  • And then the kicker from the University of Minnesota: Warm this liquid between 100 degrees and 110 degrees F; hot enough to feel the heat but not so hot that it really burns your finger. (Use a human, candy or meat thermometer if you want to make a big show of this part.) Re-cut the stems, quickly place the re-cut flowers in the vase while the water is still warm, but then immediately move the vase to the coolest spot in the house. This will force the cut flowers to take up a maximum amount of the sugar water.

(Or to directly quote the researchers: “In this brief period [the first hour after the warm vase is moved to the cool location], the flowers will take up almost as much water as in the balance of their life.”)

Valentine’s Day flowers and winter weather

Sunday is Valentine’s Day, men! And if that announcement has you heading out the door to pick up some last-minute posies, be aware of the record-breaking cold out there!

If you’re buying a moth orchid or other tropical plant, make sure it’s well wrapped before it goes outside. Get it right into a warm car and then a warm house without delay. (But once inside, display it in a cool spot for the longest run of blooms.)

Potted red tulips — the only way to say “I love you” in the Ancient Floral Code known as the Language of Flowers — are spring bloomers that can naturally handle a bit of a chill on the way home. But have them wrapped anyway to protect them from the wind. Once home, display them in a cool room, away from direct sun.

And finally, cut flowers — especially roses — do better in cold temperatures. That’s why florists keep them in refrigerated cases. But don’t put them in your fridge at home if it also contains fruit, or the ethylene gas naturally produced by the fruit will cause the flowers to drop prematurely.

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