1. Water as soon as possible
This is pretty well known, but cut flowers need to get in water as soon as possible after you purchase them. You can get them in water and then arrange, trim, or cut them as needed later in the day when you can take the time for them.
2. Fresh CUT STEMS EVERY 3 DAYS
Every two to three days, you will want to make a fresh trim at the bottom of the stem (preferably at an angle) so that the flowers will have a fresh cut to suck up the water. Additionally, before putting the flowers in the water, you will want to remove any leaves or foliage on the plant that will be submerged in water. This will help prevent bacteria from breeding and keep the water cleaner for longer.
3. Keep the Flowers out of the Sun
Contrary to what you might think, cut flowers prefer a cool, dark spot out of the way of a draft, unlike their garden counterparts. The sun will dehydrate flowers faster. Place flowers away from windows where the sun will directly shine on them, and out of the way of AC and heating vents.
4. Change the Water every 2 – 3 days
Replace cloudy and dirty water with fresh water every 2 to 3 days as needed to lengthen the life of your flowers. This will prevent bacteria from breeding and clogging up the cuts that the flowers are using to provide themselves with water
5. Couple drops of bleach to keep your water fresh
Freshly cut flowers will last longer if you add 1/4 teaspoon bleach per quart (1 liter) of vase water. Another popular recipe calls for 3 drops bleach and 1 teaspoon sugar in 1 quart (1 liter) water. This will also keep the water from getting cloudy and inhibit the growth of bacteria.