Why Plants Fail to Flower

First posted on 05-13-2010

Plants that fail to bloom can be a big disappointment for gardeners. According to University of Missouri Extension horticulturist Jennifer Schutter, the problem is usually related to the age of the plant, temperature, light, nutrition or pruning practices.

“Many plants must reach a certain age before they are mature enough to produce flowers. Fruit trees, such as apples and pears, may require as long as five or six years before they produce fruit. Gingko trees can take up to 15 years before flowering,” she said.

A stressful environment may delay flowering even further. Plants that have been budded or grafted may have delayed flowering or early flowering, depending on the type of rootstock onto which the plant was grafted. Rootstocks that restrict growth, such as those used on dwarf trees, typically produce plants that flower at a younger age than plants on rootstocks that do not limit growth.

Plants must be positioned to receive the proper amount of sunlight. Some plants flower best in full sun, others prefer cooler conditions in the shade. Peonies will flower sparsely or not at all when grown in the shade. Begonias also will not bloom well in full sun.

Cold weather may kill buds on partially opened flowers. Hot, dry weather may cause buds to dry up. Various apple cultivars and peaches require exposure to periods of low temperatures. This is also true for most spring-flowering bulbs.

Nutrition imbalances such as too much nitrogen can cause plants to produce primarily leaves and stems. The plant will be large and usually very green and healthy but will have few or no flowers.

Pruning plants at the wrong time of the year can be a reason plants fail to bloom. Spring-flowering plants such as lilacs, azaleas and forsythias begin setting next year’s flower buds in the late spring. Pruning these plants in the summer or fall may prevent flowering next year.

The best time to prune spring-flowering shrubs is immediately after they are finished flowering. Also, cutting back a plant severely can remove all the flowering wood, preventing it from flowering.

For more lawn and garden information from MU Extension, including free downloadable publications on growing various kinds of flowering plants, see http://bit.ly/MUExtLawnGarden.

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