I stumbled across this recipe for making your own flower preservative on About.com today. TIPS: To keep your cut flowers fresh you need to give them water and food, protect them from decay or infection, plus keep them cool and out of direct sunlight. Try to keep your flowers away from ripe fruit as the gases will shorten their life. Keep them in a cool area and away from direct sunlight. Flowers with milky latex-containing sap such as poinsettia, heliotrope, hollyhock, euphorbia and poppies need special treatment. The milky sap prevents water loss by the stem but in cut flowers it prevents the absorption of water. To prevent this problem dip the bottom tips (1/2 inch) of the stems in boiling water for about 30 seconds, or by flashing the tips of the stems with a lighter or other flame.