The Extension office receives many calls from frustrated homeowners whose trees and shrubs are not blooming. The expectation is for a bounty of flowers, which is not always the case. Many reasons exist as to why the plants fail to flower.
To find the root cause of the lack of flowers requires some detective work. Ask yourself the following: Does the plant have adequate light? How have weather conditions been recent? Have we had any hard freezes? Was there a drought last year? Has the plant received too much water, or has it had a lack of water? Have your azaleas or other plants been heavily pruned?
Many plants go through an aging process and must mature into their sexual stage of development, which is when they produce flowers and seeds. Some plants, such as a Ginko or Southern magnolia tree, may take 20 years to bloom. Many of our dogwoods grown from seed may take five to seven years to bloom, and then they bloom lightly. Some cultivars of dogwoods such as “Cherokee Princess” or “Barton’s White” dogwood produce blooms at a younger age. Sometimes your plants fail to bloom because they have not reached the mature stage of producing flowers.
Take the plant’s sunlight requirements into consideration. Excessive shade can prevent the formation of blossoms. Sometimes trees with a rapid growth rate will increase the shade over time, causing a reduction of the plant’s ability to bloom. Many flowering plants require full sun to thrive and produce blossoms. For instance, roses need at least six hours of direct sun each day to deliver flowers. The converse is also true. Some plants suffer in full sunlight and require shade to flower. Examples include azaleas, rhododendrons, and dogwood. Those planted in full sun will have fewer blooms and more likely to suffer from pests.
The weather conditions can also be the source of lack of flowering. Extreme cold may damage or kill flower buds, such as in the case of camellias and gardenias. Excessive heat can also reduce the formation of blooms. Both extremes can cause flowers not to form or to abort after they do form. Too much or not enough water can also be a source of issues.
Pruning at the wrong time can reduce the formation of flowers. Some form on the old wood from the previous year, and if pruned in the fall or winter, they will have limited or no blooms. Examples include azaleas, forsythias, gardenias, and big-leaf hydrangeas. Azaleas and most other early spring flowering plants form their buds after they bloom the previous summer. If you prune these plants, be sure to do so shortly after they bloom. Other plants, such as crape myrtles and most roses, have flowers on the new growth and can be pruned before they bloom. Hard rejuvenation pruning, where you cut a plant back to the ground, can also reduce or eliminate flowering. The plant becomes so vigorous that it produces excessive vegetative growth and does not slow down to set the flower buds.
Excessive vegetative growth can be caused by too much fertilization. Gardeners sometimes try to fertilize their plants into flowering with excessive amounts of nitrogen. The extra nitrogen forces too much lush, vigorous growth, and flowers do not develop as with hard pruning.
Lack of blooming is a cause for concern, but most often, the problem has a reason. Consider the sunlight and water requirements, temperatures, time of pruning, and length of time for the plant to reach a state of maturity where it can produce flowers.
One challenge mentioned was gardening in the shade; however, many plants thrive with minimal sunlight. UGA Extension Gwinnett will have an evening class online on the topic of shade gardening June 22 from 6 to 7 p.m. You can contact the Extension office to register.