“I am planning to do some pruning in my garden soon and was hoping to force some branches into flower and would like some advice on how to do this.”
– Craig Patterson, Skokie
Spring-flowering trees and shrubs such as lilacs and crab apples form their flower buds in late summer or fall before the plants go dormant for the winter. The branches can be cut and forced into bloom indoors after a period of at least eight weeks of cold temperatures that remain below 40 degrees Fahrenheit.
This is typically in late January, though each year has different weather, so your timing for forcing is OK. March is generally a good time to force branches to flower. I have had good results when pruning in the middle of March. It may take one to four weeks for the blossoms to open. The closer to their natural bloom time that you cut the branches, the sooner they will open.
Prune branches for forcing carefully, using proper techniques, and cutting off only those branches that are not essential to the plant’s basic shape. Branches should be at least one foot in length (18 inches is better), full of flower buds, and cut on a day with temperatures above freezing. Flower buds are usually larger and fatter than foliar buds. Branches with large flower buds will bloom more quickly when forced.
If you are pruning branches just for forcing, try to choose branches from denser areas of the plant. Try to remove evenly around the plant, as you will be removing some of the plant’s natural spring display. Be careful not to disfigure the tree or shrub. Otherwise, select branches from those already pruned as part of routine winter maintenance. Cut a few more branches than you expect to use because some may not absorb water properly.
Place the cut branches in a container of warm water and recut 1 inch from the base of the stem when the stems are underwater. This will help prevent air from entering the stem through the cut end and blocking water uptake. Remove any buds and twigs that will be underwater. You may want to add a floral preservative to the container water to help control bacteria. It is best to initially place the branches in a cool room out of direct sunlight and change the water every other day or so if you do not use a preservative. When the buds color up or the foliage begins to unfurl, arrange the branches in a vase and display them in a cool room in bright light but out of direct sunlight.
Some good choices for forcing include serviceberry (Amelanchier), magnolia (Magnolia), flowering quince (Chaenomeles), forsythia (Forsythia), crabapple or apple (Malus), flowering pear (Pyrus), flowering cherry (Prunus), spring-flowering witch hazel (Hamamelis vernalis), lilac (Syringa), viburnum (Viburnum), Cornelian cherry dogwood (Cornus mas) and redbud (Cercis).
For more plant advice, contact the Plant Information Service at the Chicago Botanic Garden at plantinfo@chicagobotanic.org. Tim Johnson is senior director of horticulture at the Chicago Botanic Garden.
.
