Some years some of our flowering shrubs don’t seem to put out as many blossoms as they usually do. We see the same problem in some of our flower beds. What is causing this?
Sometimes a reduced number of flowers or no flowering at all is the result of damage from marauding hordes of hungry deer. It’s almost too obvious, but the absence of blossoms could be because deer nipped the flower buds before they could sprout.
Aside from that, there are four explanations as to why your flowering shrubs won’t flower. They range from the obvious to not so obvious:
- Improper garden maintenance. Pruning too frequently or at the wrong time of year for a given plant would cause loss of blooms
- Inadequate sunlight. The amount of sunlight a plant receives may be reduced as the landscape around it matures.
- Poor soil composition. The plant may not be getting enough nutrients from the soil
- Winter damage. Plants in winter may endure erratic freezing and thawing or a late frost. That can dull the spring performance you look forward to each year.
Flowering Shrubs Age Gracefully – If You Let Them
Most plants flower more as they age. Flowering is a sign of maturity. Herbaceous perennials start to bloom in their second year of life. You don’t usually see much in the first year, but they bloom fairly well after that. A fast growing plant matures quickly where others might take years to mature.
1 The Effect of Garden Maintenance
Garden maintenance can help or hinder the performance of your flowering shrubs and perennials. One of the most common problems can be traced to improper pruning. If you prune spring blooming shrubs in winter, they won’t bloom as well because the flower buds are trimmed off in the pruning process. With summer blooming plants, overly frequent pruning can cause a reduction in flowers. Some customers want weekly pruning or shearing to maintain a particular shape or form. Since the flower always emerges from new growth, constantly cutting and shearing takes off the new flowers before they have a chance to appear.
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An example of a summer flowering shrub would be Abelia. It flowers vigorously, but a lot of people like to keep it pruned tight almost like a boxwood. To keep that shape requires almost constant pruning. So you are always removing the buds that would be flowering on that new growth. You can lose up to 60-70% of your flowers if you keep maintaining the shrub that way.
2 The Effect of Sunlight and Shade
The biggest impediment to flowering is connected to the amount of sunlight a plant receives. Most flowering shrubs require a specific number of hours of sunlight each day. And if a shade tree that was installed at the same time as the shrub has matured and spread out overhead, it could be shading the perennial or shrub. That would affect how abundantly it flowers.
3 The Effect of Nutrient Deficient Soil
If a plant isn’t producing enough food due to nutrient deficiency in the soil, it won’t be able to create the energy needed to produce flowers. But a flowering shrub will typically show symptoms of nutrient deficiency before that happens. Your garden management crew should notice that and correct it before it affects the flowering. Sometimes soil pH is the cause of a nutrient deficiency. A soil test may show that adequate nutrients are present in the soil. But if the pH is off, that can affect plants ability to uptake nutrients and result in fewer blossoms
4 The Effect of Seasonal Extremes on Flowering Shrubs
More than any other condition, a hard winter would affect blooming the most. Spring blooming shrubs such as hydrangea, are highly sensitive to late freezes or frosts in the spring. That will kill the flower buds. In the older varieties that only bloom once per year, you would lose your flowers for that year. In the newer cultivars that are re-bloomers, it will only delay the flowering. If the first round of buds got nipped by frost it will produce a second round after it has had time to grow a little. This would be the big leaf hydrangeas (Hydrangea macrophylla) that are bred for resistance to cold. A late freeze can also damage flowers on viburnum which bloom in April. It could either kill the buds completely so they never flower, or damage them so they don’t flower as well as usual.
Most summer flowers don’t mind being hot or dry. Most of the time, the hotter it is the more they flower. In fact, a cool damp summer can affect summer flowering plants adversely and may open the door to disease like botrytis (gray mold). They will still bloom but the flowers won’t be as attractive.
There are a variety of reasons why a flowering shrub might not bloom as well as it used to. In the diagnostic process, we always start with identifying the type of plant and its particular needs. Improper or overly aggressive pruning practices are often a factor. Next we look at the location of a plant and how the garden has grown up around it. We may find that it is being shaded where it had not been a few years before. It takes a bit of an investigation to find out why a plant is flowering less or not at all. Beginning with the list of possible causes above, it is a simple process of deduction.