For:
By: Daniel E. Mullins
Extension Horticulture Agent
When Flowering Plants Won’t Bloom
Shrubs
and flowers that are supposed to bloom but don’t often frustrate gardeners. Someone recently reported that nothing in
their yard would bloom, and went on to name several species that normally
flower well in this area. As in this
case, if crape myrtle, wisteria, azaleas, roses, camellias and lilies won’t
flower in a
There are several reasons that plants that normally flower won’t. The first question to ask is: are the plants adapted to this region of the country? Plants that are shipped in from other parts of the country are sometimes not as well adapted. Even some of those with the same name are different biotypes, being unlike local selections at the gene level.
Buy locally when you can. This provides better odds that the flowering plant that is purchased was produced from a locally adapted parent.
Cultural practices can affect flowering or the absence thereof. Excessively heavy or unnecessary pruning can cause flowering shrubs to stay in a vegetative, or growth stage, rather than entering the reproductive or flowering stage.
Pruning too often or at the wrong time can also prevent flowering. This is especially true of the spring flowering shrubs. Azaleas, camellias, spireas and other early spring flowering shrubs form their flower buds the previous late summer and fall. Pruning during the winter or early spring would result in flower buds being removed before they have an opportunity to open.
Over-fertilization can reduce or prevent flowering. There are two basic stages of plant growth – the vegetative or growth stage and the reproductive, or flowering and fruiting stage. If excessive nitrogen, for example is available in the soil, the plant tends to remain in the growth stage, producing new leaves and branches instead of entering the reproductive stage normally.
Stress on plants can prevent flowering. The flowering stage requires that plants expend a lot of energy over and above normal growth. In other words, in order to survive a plant will abort flower buds if it encounters severe stress.
Stress factors include too much or too little soil moisture, the lack of sufficient nutrients and too little or too much light exposure for that plant species.
Domesticated plants in particular, are not well adapted to extremes in moisture. Sometimes extremely wet sites cause root damage that is reflected in decreased growth and flowering. On the other hand a drought or the lack of sufficient supplemental irrigation can also reduce or prevent flowering.
Sometimes the plant is simply undernourished. In this case, an application of the right fertilizer in the right amount can provide remarkable results.
Perhaps the most overlooked factor is that of light. Each species has its own light requirement and some individuals fail to flower well because they are “plants out of place.” While some grow and bloom better in full sunlight, others perform best in shade or partial shade. Azaleas and camellias for example are better suited to partially shaded conditions, while crape myrtle, roses and most perennials need bright, direct light.
Question of the Week: I have a fig tree that is five years old. I thought that it was a Brown Turkey fig, but the fruit remains green. It never changes color, even when ripe like Brown Turkey does. What is wrong with my tree?
Answer: There is probably nothing wrong with your tree. Instead of Brown Turkey you could have Green Ischia, which is not widely grown but is also a desirable variety. Its fruit ripens during late July and early August.
Some
believe that because Green Ischia retains its green
color when ripe, fewer figs are lost due to feeding by birds. It is however less cold hardy than the Brown
Turkey variety and does not fruit during the summer following a severe freeze.