There are several possibilities as to why trees and shrubs do not bloom. Factors include maturity, environmental stresses, excessive lush growth, improper pruning, lack of pollinators, winter-kill, and pesticides.
Why trees and shrubs do not produce flowers
- Most flowering trees and shrubs must be physiologically mature before they are capable of blooming. During the juvenile stage of growth, plants do not produce flower buds. If trees and shrubs are started from seeds or are suckers from another plant it can sometimes take many years before they flower.
- Environmental stresses that may prevent flowering are drought, low light, excess water, winter-kill of flower buds, and late frost damage (a very common reason).
- Excessive lush growth results from excess nitrogen fertilizer, which promotes vegetative growth and fewer flowers.
- Pruning Trees and Shrubs Improper timing of pruning spring-flowering trees and shrubs will result in the removal of flower buds. Pruning at the wrong time can also result in uneven flowering if some, but not all, flower buds are removed. Most spring-flowering trees and shrubs set flower buds in late summer and should be pruned by the end of June. Lilacs should be pruned immediately after flowering. Timely pruning will allow new growth to mature enough to form flower buds in late summer. Other improper pruning methods, such as excessive pruning can result in failure to flower. Pruning is considered excessive when more than one-third of a plant is removed at a time. This type of pruning stimulates vegetative growth and results in little or no flower bud formation.
- Improper pesticide use can damage or kill flower buds.
- It is normal for some species of trees and shrubs to blossom heavily one year and not the next. They have alternate flowering patterns.