Tut tut, we had putting sugary stuff in the vase knocked out if us at floristry school, (sugar feeds the flowers, but it also feeds bacteria) best to but proper flower food, this will prolong the life. Pdq, if my memory serves me right, there s a spray but I think it is only available commercially, I'll have a look at a couple of wholesalers.
not sure what works, but I do know those little sachets they tape to a bouquet of flowers seem to make the water smell and the flowers wilt very quickly.
Quite possibly pdq though I doubt supermarkets would bother, our local Tosco does't even check the water in their flower buckets, the florist I worked in never used it either.
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