One of the best aspects of spring is the colorful floral display produced by several ornamental trees and shrubs. We wait so patiently for this spectacular spring show, that it can be a huge disappointment when it fails to occur. So why do woody plants fail to bloom? There are several factors that can contribute to a plant not blooming. The most common include
A major component of most fertilizers is nitrogen. Nitrogen promotes leaf growth in plants. Therefore, if too much nitrogen is applied, the plant will have healthy green foliage, but little or no flowers.
Most species of trees or shrubs have to reach a certain maturity to bloom. Patience is all that is required for the tantalizing blooms to appear.
Winter Kill / Hardiness
Shrubs like forsythia fail to bloom because cold winter temperatures kill the flower buds. Flower buds are less hardy than the leaf buds. Shrubs that are insulated or protected by snow cover tend to bloom below the snow line. Selecting cultivars that have hardier flower buds can reduce or eliminate this problem.
Sunlight is a requirement for many ornamental trees or shrubs to initiate flower buds. Many shrubs like lilac require a minimum of 4-6 hours of direct sunlight daily to bloom. If that requirement is not met, the plant will not bloom.
Pruning at the wrong time
Many spring flowering trees and shrubs initiate flower buds during the summer of the previous year. To ensure that the least amount of blooms will be removed from a plant, pruning of spring-flowering shrubs should be done immediately after the plant has flowered. Pruning after flowering also prevents seeds from forming.
Some blooming trees and shrubs take several years to adjust to the area in which they have been planted. Again patience and restraint should be used before opting to remove the plant.
Once these factors preventing your plants from blooming are recognized and corrected, gardeners can enjoy these beautiful plants in the landscape for many years.
This article originally appeared in the May 28, 1999 issue, p. 69.
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