The flower buds of many ornamental trees and shrubs are already fully formed at the outset of winter. After a brief period, generally eight weeks with temperatures below 40, the flower buds of several kinds are ready to open with warmer temperatures and adequate moisture. From early February through March, cut branches from these plants can be brought indoors and forced to bloom.
The easiest to force include witchhazel Cornelian cherry, red maple, forsythia, honeysuckle, pussy pillow and flowering almond. These come into bloom first outdoors when the weather moderates. It takes longer - about four weeks - to force flowering quince, lilac, redbud and bridal wreath spirea. Generally five weeks are required for forcing flowering dogwood, cherry, crabapple and pear into bloom.
Select branches that have the most flower buds. The larger, fatter buds usually are flower buds, and the smaller ones leaf buds. A few branches taken from a medium-sized shrub will not be missed.
Branches should not be cut when the weather is below freezing outdoors. If the stems are frozen, thaw them gradually before exposing them to warm temperatures. This can be accomplished by running cold water over them immediately.
Use sharp pruning shears to removes the branches. Make the cut flush with the trunk or main branch so that no stub is left. A clean, flush cut will heal rapidly.
After collecting the branches, bring them indoors and smash, crush or split the lower few inches of the stems to increase the area exposed for water absorption. Then moisten the buds and branches by immersing them in 8 to 10 inches of warm water (100 F.) for at least 24 hours.
Crushed stems may then be placed in a pail of water at room temperature for the remaining period of forcing. A piece of charcoal placed in the water will aid in keeping it sweet. Change the water every two or three days.
At higher temperatures it is more difficult to maintain high humidity and this results in bud drop. During the first few days of forcing, syringing the branches (several times daily) with warm water will aid in best developent of the buds.
An alternative method of preparing the branches is to spray them with water several times each day after keeping them in pails of warm water for the first two or three days. A piece of damp burlap should be wrapped loosely around the branches to keep the air humid. This method is particularly good if you are preparing a large number of branches. With either method, one quarter to one-half inch of the stem should be cut off and the water changed every two or three days.
Good light is important for the branches, but no sunlight. The heat of the sun's rays on a clear, sunny day is too intense for good forcing, and will fade the flowers.
When some color is evident, the branches can be removed from the pails and arranged in containers for display. Taking them from the pails will reduce the number of flowers that are bruised or broken.
Keep the arrangements in a cool place in the evening and during the day when you are not home to increase keep time.