When properly cared for, cut tulips will stay fresh in a vase of water for five to eight days. For long-lasting tulips, re-cut the stems after a few days. Lay the bouquet on wrapping paper or newspaper, and cut the stems diagonally, removing about one-half inch of stem.
Re-wrap the bouquet in paper (making a cone shape) so that the tulips are standing straight. The tops of the tulips should not extend above the top of the paper although you’ll need to allow a few inches of stems stick out from the bottom. Place the wrapped bouquet in water for an hour or two, with the paper above the water line.
Re-cut the stems once more, before rearranging, again making a diagonal cut. Fill the vase with water, adding a floral preservative – a powdery mix of plant food and bacteria inhibitors available at your florist. Although many people believe that adding a dash of carbonated lemon-lime soft drink, a teaspoon of sugar, a penny, or even a bit of bleach to the water will help extend the life of the flowers, none of these folk remedies are as effective as a commercial cut flower preservative.
The interesting thing about tulips is that they actually continue to grow after being cut, up to an inch or more. They also conform to the shape of the container, straight up if in a tall container, twisting to fit into a flat or irregular shaped vase.
Place the bouquet out of direct sun, and away from heating vents or drafts. Top off the water level daily to keep the arrangement fresh.
Excerpt from Backyard Gardener