Plant Care Articles

Why Won't My Plant Flower?

Robby Flannery, Ph.D.

Every home gardener, regardless of skill or experience with plants, has had trouble at one point to get their plant to flower.  Do not feel bad if you find yourself having the same problem.  There can be many different reasons why a plant refuses to flower.  The purpose of this article is to give some insight into what prevents some plants from flowering and how to possibly promote the production of future blooms.  Generally speaking, plants require some type of stimulus to initiate the production of floral buds.  Many of these stimuli will be covered here.

It is also important to understand why plants flower if you are going to learn how to get them to flower.  Flowers serve one purpose and one purpose only: pollination.  Plants can go about pollination in many different ways, but when it all boils down; the flower is there for that one thing.  There are some flowers that are inconspicuous.  These are generally found on plants that are wind-pollinated such as oaks, grasses and willow trees.  The more showy and attractive flowers (the ones the general population is more familiar with) are meant to attract animals to do the plants’ dirty work for them.  A bee pollinating a flower may get some nectar in return, but it is a small price for the plant to pay to make the bee unwittingly carry pollen to another flower.  Ultimately, the presence of flowers on a plant results in greater fecundity.  Knowing this, getting a plant to flower will make more sense when the various stimuli are discussed.

1.       Does the plant even produce flowers?

The large majority of plants in the plant kingdom do produce flowers, but there are some that will never produce blooms no matter what stimulus you give them.  Plants such as pines, ferns, true mosses and Ginkgos are all examples of non-flowering plants.  They may produce cones, spores or seeds but will never develop flowers.

2.       Is the plant receiving the correct amount of nutrients?

Some plants require just the right concentrations of nutrients to flower.  Some plants will remain in a vegetative state (produce only leaves and stems, but not flowers) if given too much nitrogen.  A perfect example of this is cotton.  Cotton farmers had to learn the hard way.  Dumping nitrogen fertilizer on their plants resulted in very robust vegetative growth, but no flowers that would result in a harvestable crop.  Some orchids need special fertilizer regimes too.  Providing orchids, especially those that lack a dormant period, with constant fertilizer applications year round can result in the plant staying vegetative.  By staggering the rate of fertilizer application or by disrupting the consistency of the rate of application can sometimes induce the orchid to flower.  All this makes sense especially after reading the answer to the next question.

3.       Is the plant being coddled?

Like a spoiled child, a plant that is given everything that it “wants” will not behave the way you want it to.  The stimulus to flower can come in the form of some level of stress.  The stress could be related to soil moisture, lack of nutrients (like the aforementioned orchid) or even physical stress.  Date palms usually flower after a period of cold; however the cold temperatures may not be uniform throughout a large orchard.  Date palm farmers can physically whip the trunks of the palms to induce flowering at the same time, therefore, promoting better pollination.

Being coddled makes some plants lazy.  From their point of view, plants see being coddled as living on easy street, and there is no sense of urgency to set seed and reproduce (keep in mind, plants cannot think; this is hypothetical plant psychology).  Producing flowers, fruits and seeds requires a lot of energy and without that sense of urgency; the plant will continue to lead a vegetative lifestyle.  If suddenly life on easy street disappears and a stress is introduced, the plant’s future may be in danger.  It would be best for the plant to flower and produce seeds in case the plant’s time on Earth is limited.

4.       Is the plant subjected to constant ambient temperatures all the time?

The best time of year for a plant to flower would be when the maximum number of pollinators is available.  Springtime in non-tropical climates is a great time of year to produce flowers because of the plethora of pollinators that burst onto the horticultural scene.  And what better way for a plant to know that it is spring than to sense that is no longer cold outside.  Providing a cold treatment for a plant in order to trigger flowering is very common in the plant kingdom.  Tulips are well-known for requiring a cold treatment (also known as vernalization; ‘vernal’ literally means ‘springlike’.  To vernalize means to make springlike).  A vernalization period can last from several weeks to several months at temperatures approaching freezing; however, these values can vary for different cultivars and species.  Other such plants that require a vernalization period for proper flower set are Crocus, Muscari and Hyacinths.

5.       Is the plant receiving the correct amount of light?

Similarly to temperature, light can be used by the plant to determine the time of year.  Plants native to areas far enough away from the equator where the hours of day vary during different times of year can use the amount of light to their benefit.  (To be more accurate physiologically speaking, plants measure the length of night/dark rather than the length of day/light).  Chrysanthemums and Poinsettias are examples of plants that need long nights to trigger flowering; whereas, Bellflowers and Carnations need short nights.  Commercial growers of these crops can draw shade cloth over the plants to induce longer nights or can turn on a light bulb to break up a long night, thus providing two short nights.  Much like temperature-dependent flowering, these light-dependent plants require the treatment for extended periods of time (one night of a treatment will not suffice).  The average home gardener can place a potted plant into a dark closet at night to extend the hours of dark, or use a timer to turn on a light for a plant to break up a long night.  This can be tedious work, but if it is flowers the gardener desires than it may be completely necessary.

6.       Is the plant in the right location?

A full sun plant that is placed in a shady spot may never flower.  Flowering is an expensive proposition for plants.  Once the flowering process has been set in motion, a lot of resources that could be normally used for building new leaves or expanding the plant’s root system now must be dedicated towards plant reproduction.  If there is barely enough light to provide energy for the plant to survive, the plant will not divert what little energy it has towards the flowers.

7.       Has the plant been given enough time to bloom?

Patience is a virtue.  This especially holds true with plants.  Plants work on a different time scale than people do, so getting them to flower can take longer than expected.  A gardener could potentially wait over 11 months without ever seeing a flower on a plant that blooms once per year.  Knowing when a specific plant is supposed to flower is very helpful particularly because not all plants bloom in spring.  Flowers can be found in the garden at any time of year.

8.       Is there any easy answer?  Any surefire way to get flowers?

For those gardeners who prefer to put as little effort as possible into their garden while still expecting some vibrant colored flowers, purchasing annual bedding plants is probably the way to go.  Little more than providing these plants with moisture for the roots and sunlight is needed to get them to flower, but there is little challenge to that.  An annual plant lives its entire life cycle within one growing season, which usually lasts one year.  This means that the annual germinates from seed, grows new leaves and stems, produces flowers, sets seed and then dies all in one year.  If a gardener merely provides sunlight, soil moisture and time, their garden will be full of colorful blooms with the least amount of work possible.