The trial aimed to see which flowers lasted longest and whether any treatments would extend vase life. Eleven species were monitored under seven regimes.
These included unchanged tap water, water changed every two days to limit bacteria build-up, stems re-cut under water and stems held under boiling water to kill bacteria and put in water that was left unchanged.
In other tests, substances were added, including cut flower food, a copper penny to act as a fungicide and an aspirin for acid to improve water uptake. Another regime included lemon juice for acid, sugar to feed and bleach to disinfect.
The longest lasting proved to be Zinnia elegans at 24 days, with a two-day water change, with the heads as good at 17 days as the day they were picked. An echinacea with a two-day water change lasted 22 days and an echinacea with its stems cut under water lasted 20.
Johnsons retail marketing executive Leila Russell said: "Grow your own cut flowers is very economical when compared to shop-bought, considering how long they last."