What Flower Food Actually Does
A standard packet of flower food has three ingredients that solve three different problems. Each ingredient is calibrated: too much sugar feeds the bacteria more than the flower, too much bleach damages the stem. The packet ratio is genuinely optimized — use it if you have one.
- Sugar (sucrose) — feeds the flower since it can no longer photosynthesize through a cut stem
- Acidifier (citric acid or similar) — lowers the pH of the water, which helps the stem draw water in more easily
- Biocide (a mild bleach or similar) — kills bacteria that would otherwise clog the stem
DIY Flower Food Recipe
If you do not have a packet, this is the closest home version. Mix per litre of cool water — stir until the sugar dissolves, then refresh every 2 days the same way you would with a commercial packet:
- 1 teaspoon plain white sugar
- 1 teaspoon fresh lemon juice (or 1 teaspoon clear vinegar)
- 1/4 teaspoon plain household bleach (about 2-3 drops from a dropper)
The 7-Up Trick
A surprisingly common florist hack: a splash of clear soda in the vase. Real 7-Up or Sprite combines sugar with citric acid, which covers two of the three ingredients in flower food. It does work — but only diluted.
Mix about 1 part soda to 3 parts water. Add a single drop of bleach if you want to cover the third ingredient. Skip diet soda — without the sugar there is nothing to feed the flower.
Vinegar and Sugar
Apple cider vinegar plus sugar is the most often-cited DIY recipe online. It works because the vinegar lowers pH (helping water uptake) and the sugar feeds the bloom. Use 2 tablespoons of each per litre of water.
The catch: without a biocide, sugar will accelerate bacterial growth in the vase. You will need to change the water more often — every day rather than every 2 days. If you cannot commit to that, add a few drops of bleach to the recipe.
Tricks That Do Not Help (Much)
Five popular tricks that get repeated forever but show very little effect in actual testing:
- Aspirin — small pH effect, very unreliable
- Pennies — modern pennies are zinc, not copper, and contribute nothing
- Vodka or gin — mild antibacterial at best, no nutrition
- Hydrogen peroxide — kills bacteria but also damages stem tissue at common doses
- Coca-Cola — too much sugar, very acidic, and the colour tints the water
How Much to Add and When
One full packet is calibrated for about 500 ml of water. If your vase is larger, scale up proportionally. Add flower food at every water change, not just on day one — the sugar gets consumed and the biocide breaks down within 48 hours. See the full care routine for the timing.
