Is it a good idea to add sugar or other things to the water for cut flowers?

Question

Mostly for future reference, is it helpful to add sugar or other things to the water meant for cut flowers?

There seems to be conflicting data from different sources. See How can I preserve a bouquet of flowers for two days before gifting them?

I've heard that the sugar:

• feeds beneficial bacteria
• feeds the plant (which I know to be wrong, plants don't metabolize sucrose)
• helps prevent air bubbles

But none of this has been satisfactorily been shown true for me. My experience says 'use plain water', and then masteragardeners.org tells you to add all kinds of things to the water. Some people even say a copper penny helps.

Let's get this straight once and for all.

Answer 1

The fine folks over at UMass have some information on this:

http://extension.umass.edu/floriculture/fact-sheets/sugar-and-acidity-preservative-solutions-field-grown-cut-flowers

And similarly, Scientific American had an article back in 2007 quoting several professors on the subject:

http://www.scientificamerican.com/article/fact-or-fiction-vodka-citrus-sodas-keep-flowers-fresh/

To summarize these - there's a need to provide some flowers with a bit of sugar to help feed the flowers. The acidic component (citric acid, usually) helps to lower the pH which allows the water to travel up the flower more easily. Adding a little bleach to the water helps to combat the bacterial growth.

I think that the UMass information in particular is useful, particularly the table in the later part of the article where it provides information for a variety of flowers.

The studies they cite indicate that the amount of sugar (if any) needed varies. Tulips, for instance, don't really benefit from the sugar but would benefit from a little bleach in the water. Interesting stuff.

Answer 2

Completely anecdotal, but I've always had great success with adding an aspirin tablet to the flower vase. I've also done without it, and it seems to me that they definitely stay longer with it.

I just did a little research, and it seems this works because flowering plants tend to like slightly acidic soils. Aspirin is an acid.

Aspirin is the drug name for acetylsalicylic acid, a powerful painkiller. The soil that most flowering plants prefer is acidic, as it makes certain nutrients more readily available to them.

source

According to the same article, a small amount of sugar would also be beneficial as it adds nutrients to the water.

All plant cells need nutritional sustenance to survive, and this is normally provided by the sugars produced by photosynthesis, the method by which plants use the sun's energy for food production. The process stops once the flowers are cut and moved out of direct sunlight; adding sugar to the water keeps their cells fed a little longer.

While certainly not a scientific journal, this is some common sense stuff here.

As for the copper penny, that is your anti-bacterial. Copper has anti-microbial properties and will stave off our little friends that want to decompose the flowers for a little while. Note that it has to be a copper penny, so pennies made after 1982 won't work.