On receipt of your flowers, please make sure that you cut your stems at a 45 degree angle (known as an oblique cut in the industry) before placing in clean water and a flower food sachet.
Your flowers will only take what water they require up their stem, therefore you must cut every two to three days to allow the flower to replenish its store of water and nutrients, remembering to also change and use clean water at the same time with flower food.
Most problems affecting the flowers life can be put down to the above lack of care. An old florists tip to keep your long stem Tulip's and Gerbera's 'straight' is to wrap your bunch in one sheet of old newspaper and straight into a bucket of water and place in a cool & darkened room for an hour or two.
Please never forget to enjoy your flowers, they are a living thing ...