Hydrangea blossoms are often used in wedding floral arrangements as well as floral arrangements displayed in the home. The large flower heads are actually a collection of many small flowers. Hydrangea blossoms may be blue, pink, green or yellow. Although hydrangea blossoms cut from the garden have a short vase life in a floral arrangement, which means they wilt quickly, you can extend the vase life with a simple procedure.
Cut hydrangeas when nearly all of the flowers are open. They should be firm to the touch with no wilted flowers within the flower head. Cut flowers in the morning even if dew is still on the flowers. Cut the stems as long as needed for arrangement and add an extra inch. Immediately place stem end in container of fresh, clean water and cover the flowers with a water-soaked, light cotton cloth. A heavy cloth will press down on the flowers and ruin their shape.
Prepare an area to condition the hydrangeas with alum poured in a shallow dish or bowl, a pan of boiling water and container with fresh, cool water. Alum is available in the spice section of most grocery stores.
Condition each hydrangea bloom by cutting at least 1 inch off the bottom of the stem, then dipping 1 inch of the stem end into the boiling water for three seconds, protecting the flower head from any steam. Dip 1 inch of the bottom of the stem into the alum. Tap off the excess alum and place the stem end into cool, clear water. Have enough cool water in the container to cover at least the bottom third of the stems.
Cover all flower heads with a light cotton cloth dampened with cold water. After five hours the hydrangea flowers should be ready for arranging, and the vase life will be extended considerably.