To keep the flowers alive, pop each stem into a small florist's vial filled with water that can be hidden among the twigs. Forcing large flowers such as June-blooming rhododendrons is extremely difficult, especially without a greenhouse, says Leach. The plant has to generate an enormous amount of energy to push open the bud scales of the huge blooms. Home gardeners will have better luck forcing early, small-leafed varieties such as R. mucronulatum , PJM hybrids, whose bright purple flowers you see everywhere in April, and early azaleas. Any water you add should be at least room temperature.
Leach advises that the water be changed daily to help prevent mold growth.
Adding a packet of floral preservative or a bit of Sprite, which contains citric acid, also will keep bacteria from fouling the water. Leach also notes that the plants will do best if kept in a humid environment. The branches do not need light until buds begin to grow. Leach recommends wrapping the tops of the twigs in plastic or damp newspaper fastened loosely with string or tape. When buds start expanding, usually within a few days to a week after cutting, these wrappings should be removed.