When it comes to bloom, winter holds little bounds for those who want to bring a bit of spring into their home. Winter has challenges of floral enjoyment outside as scarcity of bloom can be found in the landscape. Forcing blooms indoors can create a fascinating alternative to the winter doldrums. Although there are a few exceptions, most flowering trees and shrubs have a dormancy requirement fulfilled through forcing when branches are harvested from February to March.
Some characteristics to look for in bud development are healthy buds that are large enough to produce flowers. Immature buds will not force successfully. There are variations in capacity to flower as floral bud development is influenced by light and the outer branches will be more suitable for forcing. Flower buds will be more plump and round than leaf buds.
Shorter days mean less blooms in the landscape, but with a little planning you can continue bloom indoors throughout the winter. Look at the natural phenology (season of bloom) of woody plants you are considering forcing. Forsythia, Hazelnut, and Witchhazel are early bloomers suitable for harvest in January and have a relatively short amount of weeks until bloom. Usually the plants that bloom earliest are the easiest to force indoors.
Branches can be cut and forced to bloom to determine if the dormancy requirement has been met by the tree or shrub. If forcing fails, the plant may not have received enough chilling hours. Try again in a couple weeks as it is an inexpensive effort. Cut the branches at a strong angle and place the stems immediately in water to ensure good water uptake. Recutting stems underwater will also aid the quick absorption of water. Selecting larger branches and cutting back to the base of the plant can be beneficial to select the best buds possible under closer examination. Remember the health of the plant and the typical pruning methods when selecting branches.
Many of our branches can be pruned at least 10 to 18 inches long depending on their use. Select branches that are less that 1/2 inch diameter. Pruning is best accomplished when temperatures are above freezing. Branches may be soaked in buckets or immediately placed in vases with warm water. The water will need to be changed daily and be sure to check the water level often and refill as necessary.
Plastic bags can be placed around the stems to increase the humidity. Increasing the moisture helps to loosen the bud scales and helps them to readily fall away as the flowers expand.
Keep the branches in a bright, but not sunny location. Placement near a bright window works, but be cautious of heat registers nearby and avoid direct sunlight. Forced branches will last longer if moved to a cooler location once forcing has begun. All that is required for buds to burst is an increase in warmth and moisture.
Andrew Holsinger is a University of Illinois Extension educator, horticulture.