"Flower food" explained

What is cut flower food?

Q: What is actually in those packets of cut flower “food”? Is it just a preservative to make them last longer in the water? Is it possible to make it oneself?

--- Mrs Jeni Butler, via email

A: The contents of those little sachets is a mixture of sucrose (sugar), acidifier and something that inhibits the growth of bacteria.

Sucrose serves as a source of energy to make up for the loss of the functioning leaves and ensures continued development and longevity of the flower. Most water supplies are alkaline and can reduce the life of cut flowers, so the acidifier makes the pH of the water closer to the more acid pH of the plant’s sap. It also acts to stabilise the pigment and the colour of the flowers.

A microorganism growth inhibitor is perhaps the most important part of the “food”. Bacteria quickly starts to proliferate in the vase water (especially if damaged leaves are left clinging to flower stems prior to dunking).

Many gardeners/florists swear by various ways to keep flowers fresher for longer. But aspirin, wine or copper coins added to the water are apparently ineffective. Home-made concoctions are not as good as the packet stuff, either (according to the people who are in the business of selling flower food, anyway).

However, variations of the following recipe seem to be favoured by many. To make one litre of the solution...

Directions for DIY at the Telegraph source column.   I hope the "growth inhibitor" is a natural and not a pharmaceutical antibiotic.