Daffodil flower stems and leaves have a sap that can irritate your skin if you are sensitive to it so check it out and wear latex or vinyl gloves if you are sensitive.
Gather your flowers early in the morning when the plants have maximum water content. For single flowered kinds, choose stems with buds that are showing color. The bud should be at a 45-degree angle to the stem and the brown papery covering the bud should be split. Multi-flowered varieties should have at least one flower open. Pull the whole stem at an angle from the base with your fingers. A sharp knife or special florist shears may be used but never use secateus. Do NOT cut any leaves as they are needed to produce food for the bulb.
Indoors, recut the stems at a 45-degree angle making sure that you cut above the white pith. Place the cut stems in 6” of cool to tepid prepared water containing bleach at the rate of ¼ teaspoon/quart water. Warm water will cause the buds to open more quickly. Put the container of stems in a cool, dark area or 6 to 12 hours. Do not condition other flowers with daffodils, as the sap can be toxic to them.
When arranging the flowers rinse off the daffodils that will be combined with other kinds of plant material. The use of foam in mixed arrangements will help contain any toxic sap that remains in the daffodils. Daffodils are especially pretty with other spring blooming plants such as hyacinths and iris. For the longest vase life, arrange the daffodils alone in a few inches of water-beach mix with no foam.
Change the water-bleach mix in your arrangement every 2-3 days. This slows the growth of bacteria that clog the water conducting tissue of the stems.
Keep your arrangement away from drafts and heat as much as possible to keep it looking fresh for the longest amount of time.