The plump, round flower buds on this crape myrtle assure that blossoms are on their way. Many issues can cause plants to fail to bloom. Contrary to popular belief, lack of fertilizer is one of the least common.

One of the questions I am often asked is why a plant does not bloom. Often the asker wants to know what type of fertilizer they need to apply to make the plant flower, but the answer is usually not that simple. Whether discussing a tree, shrub, perennial, or vegetable, there are many reasons plants fail to flower. Getting them to bloom depends upon correctly identifying what is preventing flower production – and the answer is rarely lack of fertilizer.

Too Much Shade

‘Made in the shade’ may be a great motto for summer but it does not apply to flowers. Flowering requires a lot of energy, much more than just making leaves. Plants get this energy from sunlight, through the process of photosynthesis. If sunlight is limited, energy production is reduced. When plants do not have enough energy to meet all their needs, flowering is usually the first thing they cut out.

Unless they are shade lovers, most plants need at least six hours of direct sunlight a day to bloom well. This is especially true of vegetables, fruits, crape myrtles, roses, and most annuals and perennials. Sometimes shade increases gradually as trees overhead grow and fill in. If you have a plant that bloomed well a few years ago but does not now, take a look to see if the amount of shade in the area has increased.

A Matter of Maturity

Some plants must reach a certain age before they can flower. This is especially true of trees and shrubs grown from seed. For example, southern magnolias can take up to ten years to bloom when grown from seed, while dogwoods and camellias often take five or six. Most perennials will not bloom the first year when grown from seed. Even when grafted, fruiting pears and pecan rarely bloom before they are eight years old.

In other cases, it may not be the right time of the season yet. For example, there are early and late blooming varieties of crape myrtles. Early varieties are flowering now, while late blooming varieties will not open their blossoms for another month. An even more curious example is that of cucumbers, squash and melons. Known as cucurbits, these vegetables produce separate male and female flowers on the same plant. Only the female flowers will make fruit. When they first start to flower, cucurbits produce male flowers only; leading gardeners to think their plants are barren. After a few weeks though female flowers will begin to appear alongside males, enabling fruits to be produced.

Pruning Problems

Sometimes plants fail to flower because they are pruned at the wrong time. This is most common with spring flowering shrubs like azaleas, Indian hawthorn, blueberries, hydrangea and camellias, which make flower buds in the late summer and fall. If they are pruned in fall or winter before they bloom, all the flower buds are cut off, which is why it is important to wait until after they bloom to prune spring flowering shrubs.

Pruning too severely can also reduce flowering because it does not allow plants to build up enough energy to make blossoms. A good example of this is daffodil bulbs. Gardeners will often cut the leaves of daffodils and other bulbs off while they are still green. If this is done for a couple of years in a row, the bulbs will usually stop blooming because they were not able to store enough energy to make flowers.

Correct Nutrition

Fertilizer can play a role in flower production, with either too much or too little causing problems. Plants that are over fertilized often produce lush growth and lots of dark green leaves but few flowers. This is most often seen in vegetables like tomatoes and beans.

On the other hand, plants that are starved rarely flower well. When this is the case you can usually tell the plants need nutrients long before flowering is affected. Common symptoms include stunting and yellowing leaves. Other conditions that stress plants, such as drought and extreme heat, will also reduce flowering. In all cases, you must understand what is causing your plants not to bloom before you can fix it.

Learn More

If you have questions about plant problems, contact your local Extension office. If you live in Pender County, call 259-1235. In New Hanover County, call 798-7660. In Brunswick County call 253-2610, or visit https://www.ces.ncsu.edu/where you can post your questions to be answered via the ‘Ask an Expert’ widget.