The Science of Keeping Flowers Fresh

Everyone seems to have their favorite method for prolonging the life of fresh-cut flowers.

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Drop in a penny… spritz with a sugary soda… stir in vinegar… or give the flowers an Aspirin (which might be needed after all of that other stuff). While many of the remedies do little to help keep the flowers fresh, there’s some interesting science behind all of these formulations to help keep your flowers fresh.


Let’s start with the recommendation from the professionals – the florists. They recommend using commercial flower preservatives. The additives work by providing food in the form of sugar, fighting the growth of harmful microorganisms and allowing the plant to take in nutrients more efficiently by raising the acidity of the water (lowering its pH).

Some of the most common homemade solutions include the following…
Fresh Flowers Variables

  • Sugar – A sugar solution can provide food for the flower, but it will also promote the growth of microbes.
  • Bleach – A few drops of bleach will help to control the growth of bacteria – the slimy stuff you see on the leaves in the water.
  • Vodka —  Vodka, or any alcohol, may have a preserving effect halting ethylene production which is the ripening gas that makes flowers wilt.
  • 7-Up or Sprite — Citrus soda, such as 7 Up and Sprite, can effectively make flower water both acidic and sugary. Experts recommend mixing up a solution of one part soda and three parts water, along with a few drops of microbe-killing bleach. Sodas makes the water more acidic, which means it can travel up the stem of the flower more quickly. Also, the sugar serves as food for the flower.
  • Apple cider vinegar & sugar — Flowers need sugar as food. Sugar is a substantial ingredient in flower food packets. The problem is, sugar accelerates bacterial growth… you get those gunky, slimy leaves around day 4 to prove it. The solution is to add an acid. Vinegar acts as a bacteria-fighting agent to combat any damage the sugar creates.
  • Pennies – According to 2004 article in the Florists’ Review Magazine, pennies do not prolong the life of fresh-cut flowers. The genesis of the idea cam from the notion that copper is a great fungicide, but the copper in pennies is not soluble in water. Good idea… but the science doesn’t support it.
  • Aspirin — Whether aspirin (acetylsalicylic acid) can effectively lower the pH of water and extend the life of fresh-cut flowers is up in the air. Some studies have found a positive benefit to using ground-up aspirin, while others have not.
  • Refrigerator — Cold temperature slows aging of the flower.

The Flower Experiment

So… what’s the best formula for keeping flowers fresh? FTD florists conduced an experiment using five of the same flower arrangements. In each vase, they put a flower food packet along with 2 cups of lukewarm water. The five variables in the test included vodka, Sprite, apple cider vinegar & sugar, aspirin and just moving the flowers to the refrigerator at night. The test was conducted over a seven day period. The water was changed on day 3 and all of the additives were replaced.

The results were interesting, to say the least. The vase with Sprite did fine on days 1 and 2 but started to fade on day 3 and was a slimy mess by day 5. The vase with the vodka also did fine on days 1 and 2 but looked droopy and had grayish stems by day 4. The researchers didn’t find the aspirin to have any preserving effects, though it did not kill the flowers faster, either. The flowers in the vase with apple cider vinegar and sugar did surprisingly well. The combo held its own in the survival-of-the-fittest trial.

Drum roll… coming in as #1 in the test was… the refrigerator! Every night before retiring to bed, the flowers were placed in the refrigerator. After a cold 8 hours of rest, the vase of flowers returned to it’s daytime home on the dining room table. Believe it or not, the cooler temperatures kept the flowers fresh through day 7. Maybe this is why florists keep their flowers inside a large refrigerator. However, the apple cider vinegar and sugar solution came in a VERY close second place in the experiment. So, if you don’t have a giant refrigerator, you might give it a try.

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