Change, do not top up
Topping up old water leaves the bacteria that close a stem. Empty the jar entirely, rinse it, and refill with cool water; the extra minute doubles the life of a summer bunch.
Recut the stems by a centimetre every second change, always at an angle and under running water, so the flower can keep drinking. Remove leaves below the line and any bloom that has passed, without sentiment.
Give them a night shift
Flowers kept cool after dark open more slowly and last longer. A hallway windowsill away from the radiator suits them; the bedroom suits you less, since their water and your sleep prefer different temperatures.
If a bunch wilts in the afternoon heat, a full cool bath for an hour often revives it. Cut flowers are hardier than they look, which is part of their lesson.
Published by the Fiorlume journal.