Why Trees and Shrubs Fail to Flower

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It can be very difficult if not impossible to pinpoint the exact reason a plant doesn’t flower. The following are some of the possibilities:

  1. Sunlight or its lack. Plants capture sunlight and convert it to food which is stored energy. Flowering and fruit production are energy consumers. Shade may mean the plant can’t capture enough energy for flowering. Sometimes a plant quits flowering as a result of the growth of plants around it producing more shade.
  2. Competition. Adjacent shrubs, trees, grasses, bedding plants, or weeds may be competing for water, nutrients, or sunlight.
  3. Planted too deep. When roots are too deep, their supply of oxygen is limited which in turn limits photosynthesis. Limited photosynthesis means not enough energy to bloom and may result in the death of plants.
  4. Pruning. Pruning at the wrong time may remove flower buds. Winter and spring flowering shrubs generally produce buds during the summer. Pruning during late summer, fall or winter may remove the buds. For summer flowering plants, pruning in late spring or early summer may remove their buds.
  5. Sucker growth. Excessive sucker growth at the base of a plant may function as an energy sink possibly reducing or eliminating flowering. Generally, sucker growth should be removed from its point of origin.
  6. Maturity. Many plants must reach a stage of sexual maturity in order to bloom. For some, this requires several years, generally seven years for a seedling dogwood and up to 15 for a southern magnolia. A newly planted tree or shrub, although technically mature and even if it bloomed in container or field prior to transplanting, may devote all its energy to growing new roots before it will bloom again.
  7. Extreme temperature. Flower buds can be killed by extremely low winter temperatures. Plant selection should include consideration of the suitability of the environment for the plant. Plants not adapted to southern climates may use energy (respiration) so rapidly that photosynthesis cannot keep up. The result is not enough energy for flowers. Even if these plants have flowered before in the same location, conditions may vary sufficiently from year to year to produce consistency.
  8. Soil chemistry. There is no need to guess. Every plant needs the same 17 nutrients. Most of them are sufficiently available, carbon and hydrogen for example. Those which need to be supplemented can be determined by a soil test. Some nutrients applied in excess can interfere with the uptake of others and reduce blooming as well as general plant vigor. Excess nitrogen can lead to vegetative growth instead of flowering. Excesses of potassium, calcium, or magnesium can induce an excess uptake of that nutrient at the expense of the others. The North Carolina Department of Agriculture and Consumer Services (NCDA&CS) operates a full-time soils lab in Raleigh. There is no charge for a complete analysis and recommendation. You can get the necessary forms and boxes from the NC State Extension.

Plants may fail to flower for one or more of the reasons presented here. Review your plants’ history and growth pattern to determine possible reasons for failure to flower. And remember to notice details even when things are going right. You have to know what it’s supposed to look like in order to recognize when something is wrong.