It can be disappointing to see a plant grow and flourish but never see a bloom. There are many reasons a plant doesn’t flower as expected. The good news is nearly every plant will flower – eventually.
Working out why there are no flowers takes some detective work, but once you’ve worked out what is causing the lack of flowers, it may be possible to fix the problem or at least be more patient as things fix themselves.
As a rule of thumb, most plants flower annually at a certain time of year. Most of the plants we grow in our gardens flower in spring but there are plants that have their main flowering in other seasons. For some plants, that annual flowering is their only flowering, but others can be relied on to bloom for many months. These plants are known as repeat flowering. A light pruning of a repeat flowering plant usually encourages new growth and more flowers. Modern roses are a good example of plants that repeat flower from spring to autumn.
Other plants may flower prolifically at one time of the year and then have odd flowers at other times. This is called spot flowering. Wisteria, jacaranda and azaleas are all examples of plants that spot flower outside their main flowering period.
To start the detective work, ask yourself if the non-flowering plant has never flowered at all, or has flowered but not recently. Where a plant has never flowered, it may not be old enough to bloom. Many plants, especially trees and some woody shrubs, take years to reach a mature stage. A plant grown from seed, can take seven to 10 or even more years for flowers to appear.
Occasionally, plants that are cutting-grown may not bloom at all. This is because they’ve been inadvertently grown from a piece of non-flowering stem (known as ‘blind’ wood). It is very rare, but can occur!
In the case of the so-called century plant (Agave americana), which is grown from offshoots or ‘pups’, it can be decades before the plant blooms – but usually not the 100 years suggested in its common name. When you learn that this agave flowers and then dies, it makes the long waiting time understandable!
If lack of maturity is the cause of the non-flowering, simply wait a few more years (or decades) and the plant will bloom. Try to avoid pruning while you wait, as this may delay flowering. Some magnolias for example take many years of growth before they bloom.
Used to flower, but now it doesn’t
If a plant did flower but has now stopped, there are a host of possible reasons for the lack of flowers. These range from physical reasons to poor or adverse growing conditions. Physical reasons include that something is eating the buds (such as possums or birds), frost at the wrong time killed the buds, or the plant was pruned at the wrong time of year.
Frost & cold
A late frost or cold may kill buds on deciduous flowering plants such as ornamental fruit trees and can also delay blooms on broad bean or sweet peas. Some plants also need a specific period of winter chilling to occur before they bloom. If the right amount of cold isn’t experienced then the plant won’t bloom. Cherries and apples are examples of deciduous fruit trees that need winter chilling. They’ll bloom poorly – or not at all – after a warm winter.
Hard pruning a plant that flowers on new wood at the wrong time of year can mean a year with no flowering. To avoid this error, prune plants after flowering. Plants that may not flower for a year if pruned at the wrong time include wisteria and hydrangeas that are heavily pruned in late winter. Spring-flowering bulbs such as daffodils that are cut back after flowering but while they are still in leafy growth may also fail to re-flower as they’ve been unable to store the nutrients needed for the following year’s blooms.
Poor or adverse growing conditions that stop or delay flowering include too much shade, lack of water, over or under fertilising, high temperatures or over crowding. A plant that needs full sun, can fail to flower if it is growing in shade. Often as a garden matures, plants that were in full sun and flowering well become overshadowed and so fail to flower. This can occur with roses and agapanthus. The solution is to move the plant into a sunnier situation, or to prune back surrounding growth to allow in more light.
Dry conditions can lead to poor or no flowering. Increased watering of plants that don’t flower is often the only stimulus needed to bring about that long-awaited flower.
Plants that get the right amount of nutrients also flower better than those that are either starved or over fed. Most flowering plants respond to a feed with an all-purpose or flowering fertiliser applied in spring. Repeat flowering plants such as roses, dahlias and annuals, continue to bloom with regular applications of fertiliser in summer and early autumn.
A plant that’s lush and leafy but has no flowers, may be getting over-fertilised with a high nitrogen fertiliser that encourages leafy growth at the expense of flowering. Hold off the feeding or switch the type of fertiliser that’s used and follow the instructions on the packet or container to assure the right amount is being applied.
Some plants also stop flowering when temperatures climb. Tomatoes for example can stop flowering when temperatures are over about 35C. Once temperatures drop, flowering will resume.
Plants that are overcrowded may also fail to flower. Plants that naturally form clumps such as narcissus bulbs, cymbidium orchids and many perennials produce fewer flowers when the clumps get big. This is probably due to lack of water and fertiliser but the solution is to dig up the clump, divide it or split up the bulbs, and replant them into soil that’s been refreshed with compost or nutrients or, if the plant was growing in a container, fresh potting mix.