Why Is My Plant Not Flowering? The Australian Gardener’s Guide

Your plant is enormous.

Green.

Healthy.

Possibly growing with slightly more enthusiasm than you'd like.

There is just one small problem.

It refuses to flower.

So you fertilise it.

Still nothing.

You give it more water.

Nothing.

You stand beside it looking accusingly at the neighbour's version, which is covered in flowers despite appearing to receive absolutely no care whatsoever.

Still nothing.

And this is where gardening gets interesting, because a healthy plant and a flowering plant are not necessarily the same thing.

A plant can be spectacularly good at growing leaves while having absolutely no intention of producing flowers.

Why?

Because flowering isn't the plant's first priority.

Staying alive is.

And before we start throwing potash, fertiliser, banana skins, Epsom salts and whatever else the internet has suggested at the poor thing, we need to work out what's actually happening.

First question: is it getting enough sun?

Start here.

Seriously.

Before buying anything, adding anything or digging anything up, work out how much direct sunlight the plant actually receives.

Not how sunny you think the garden is.

Not whether the label said “full sun” when you planted it four years ago.

Actually watch the spot.

A plant needs energy to grow and reproduce, and that energy ultimately comes from light.

Many flowering plants can survive in lower light than they need to flower really well.

That's an important distinction.

Your plant may look perfectly healthy.

It may have lovely green leaves.

It may even be growing.

But if it isn't receiving enough light, flowering can be disappointing or nonexistent.

And gardens change.

The little tree you planted beside it five years ago may now be casting shade for half the day.

The neighbour's hedge may have grown.

The pergola might now be covered in a vine.

A position that once received six hours of sun might now receive three.

So if a formerly flowering plant has stopped flowering, don't just look at the plant.

Look at what has changed around it.

More leaves can actually be a clue

This one catches people all the time.

The plant isn't flowering, so we feed it.

Then it grows even more leaves.

Still no flowers.

So naturally we feed it again.

Congratulations.

We may now have the healthiest non-flowering plant in the suburb.

😂

Nitrogen is an essential plant nutrient and plays an important role in leafy vegetative growth.

But excessive nitrogen can encourage lush foliage at the expense of flowering in some plants.

That doesn't mean nitrogen is bad.

Plants need it.

It means more fertiliser isn't automatically the answer to every plant problem.

If your plant is already producing loads of vigorous, dark green leafy growth but very few flowers, ask what you're feeding it before adding more.

This can be particularly relevant when plants are growing beside lawns that receive regular high-nitrogen fertiliser.

The hedge may be quietly enjoying the lawn's dinner too.

Stop fertilising problems you haven't diagnosed

This probably needs to become a general gardening rule.

Plant yellow?

Fertiliser.

Plant small?

Fertiliser.

Plant not flowering?

Fertiliser.

Plant looked at you strangely?

Fertiliser.

We love fertiliser because it feels like we're doing something.

But fertiliser solves nutrient problems.

It doesn't solve insufficient sunlight.

It doesn't fix pruning at the wrong time.

It doesn't make an immature plant mature.

It doesn't change the season.

And it won't magically make a plant flower if environmental conditions aren't suitable.

Before feeding, diagnose.

Your wallet and your plants will both appreciate it.

You may have pruned the flowers off before they existed

This is a big one.

Different plants produce flowers on different types of growth.

Some flower on fresh new growth.

Others form flower buds on older wood.

Some begin developing next season's flower buds surprisingly soon after the current flowering period finishes.

Which means if you prune at the wrong time, you can remove the buds that would have become flowers.

The plant isn't broken.

You cut the flowers off months before you knew they were flowers.

This is why blanket advice like “prune everything in winter” doesn't work.

Before pruning a flowering shrub, find out when and where that particular plant produces its flower buds.

A plant that flowers on new season's growth may respond beautifully to pruning at the appropriate time.

A plant that already has next season's flower buds sitting on older growth may respond by producing precisely zero flowers and leaving you wondering what happened.

Timing matters.

Your plant might simply be too young

We are terribly impatient gardeners.

We buy a plant.

We plant it.

And approximately fourteen minutes later we'd like flowers.

Some plants oblige.

Others need time.

Plants go through juvenile and mature stages, and some species won't flower until they've reached sufficient maturity.

This is especially relevant with plants grown from seed.

A seed-grown plant may need considerably longer to reach flowering maturity than a plant propagated vegetatively from mature material.

Fruit trees are a classic example, but the principle applies more broadly.

If your young plant is otherwise healthy and growing well, there may be absolutely nothing wrong.

It may simply not be old enough yet.

It might not actually be flowering season

This sounds painfully obvious.

And yet.

Nurseries can make seasons confusing because plants may arrive from different growing conditions, production environments and climates.

Then there's social media.

You see someone's Gardenia flowering beautifully online and wonder why yours isn't.

Except they're in Queensland and you're in Victoria.

Or the photo was taken four months ago.

Or they're in the Northern Hemisphere.

Plants have natural flowering periods influenced by genetics, temperature, day length and environmental conditions.

Some flower once spectacularly.

Some flower repeatedly.

Some flower for months.

Some wait all year, put on an outrageous display for three weeks and then go back to being leaves.

Before deciding your plant has failed, check when it is actually supposed to flower where you live.

Temperature can affect flowering

Plants don't own calendars.

They respond to environmental signals.

Temperature can influence flowering in many species, and different plants have evolved very different strategies.

Some plants require exposure to a period of cooler temperatures before flowering properly.

Others need warmth.

Extreme heat can interfere with flowering or cause buds and flowers to drop.

Cold snaps can damage developing buds.

This is one reason the same plant can behave differently from one year to another.

Gardening isn't happening in a laboratory.

Weather changes.

Plants notice.

Day length matters too

Here's one of the cooler bits of plant biology.

Some plants can effectively measure the changing length of day and night.

This process, called photoperiodism, helps certain plants time flowering to particular parts of the year.

Some are described as short-day plants.

Others are long-day plants.

Others are day-neutral.

The biology is more complicated than the names suggest, because plants can actually be responding critically to the length of the uninterrupted dark period.

But the useful gardening lesson is this:

Plants can tell that the seasons are changing without looking at the calendar.

Changes in light help trigger biological processes inside the plant.

So when something flowers at almost the same time every year, it isn't necessarily coincidence.

The plant is reading its environment.

Which is frankly impressive considering mine don't even have Wi-Fi.

Water stress can stop flowering

Flowers are expensive.

Not financially.

Energetically.

A plant needs resources to produce buds, flowers and eventually seeds or fruit.

When a plant is under serious water stress, survival becomes more important than reproduction.

Flower production may decrease.

Buds can abort.

Existing flowers can drop.

But this doesn't mean drowning a non-flowering plant will make it bloom.

Too much water can create root problems, reduce oxygen around the roots and cause a completely different type of stress.

Again, we're looking for appropriate moisture.

Not maximum moisture.

Check the soil.

Always check the soil.

Sometimes a little stress can trigger flowering — but please don't torture your plants

This is where gardening advice can get dangerous.

Some plants can respond to particular forms of environmental stress by shifting towards reproduction.

Which makes biological sense.

If conditions are becoming difficult, reproducing suddenly becomes rather important.

But that doesn't mean you should deliberately half-kill every non-flowering plant in your garden.

Stress severe enough to trigger flowering can also be stress severe enough to damage the plant.

Different species respond differently.

The useful lesson isn't “stress your plants.”

It's that flowering is part of a plant's reproductive strategy and environmental conditions influence when that strategy is activated.

What about potash?

Ah yes.

The gardening world's answer to every flower-related question.

Potassium is an essential plant nutrient and is involved in many plant processes, including water regulation, enzyme activation and overall plant health.

But potash isn't a magical flower switch.

If your soil already contains sufficient potassium, adding more doesn't necessarily create more flowers.

And if your plant isn't flowering because it's sitting in deep shade, you can give it all the potassium you like.

It's still sitting in deep shade.

Use fertilisers according to plant requirements and label directions rather than treating individual nutrients like gardening spells.

What about phosphorus?

Phosphorus is another essential plant nutrient involved in processes including energy transfer and root development.

It's commonly marketed heavily around flowering.

Again, plants need it.

Again, more isn't automatically better.

And this is particularly important when growing Australian natives.

Some Australian plants — notably many members of the Proteaceae family — are adapted to low-phosphorus soils and can be sensitive to excessive phosphorus.

So please don't throw high-phosphorus fertiliser around the native garden because somebody on Facebook said phosphorus makes flowers.

Choose a fertiliser appropriate to the plants you're actually growing.

Why did my plant flower last year but not this year?

Now we become detectives.

If the plant flowered previously, something may have changed.

Was it pruned differently?

Did you prune later?

Has the position become shadier?

Was winter warmer or colder?

Did you apply a different fertiliser?

Has irrigation changed?

Was there extreme heat while buds were developing?

Did frost damage them?

Was flowering unusually heavy last year?

Some plants naturally have stronger flowering years than others.

The important thing is to stop looking at the plant in isolation.

What changed around it?

Gardening problems often make much more sense once you ask that question.

Why are the flower buds forming and then falling off?

This is different from a plant that never produces buds.

If buds are forming, the plant has already started the flowering process.

Now something is interrupting it.

Possible causes can include sudden temperature changes, water stress, excessive heat, root stress, pests or other environmental conditions.

Gardenias are a classic plant people notice doing this.

You watch those beautiful buds developing for weeks.

You begin emotionally planning their future.

Then they're on the ground.

Rude.

Consistent care becomes particularly important while a plant is budding and flowering.

Big swings between extremely dry and extremely wet conditions can be stressful.

Should I deadhead flowers?

For some plants, yes.

Remember what flowers are for.

Reproduction.

Once pollination occurs, many plants begin putting energy into producing seed.

Removing spent flowers before seed develops can encourage some repeat-flowering plants to continue producing flowers.

This is called deadheading.

It doesn't work the same way with every plant, and plenty don't need it.

But with plants that respond well to deadheading, you're essentially interrupting the reproductive process.

The plant says:

Right. That didn't work.

And sometimes has another go.

Which is quite funny when you think about it.

Why are my plants flowering but the flowers are small?

Now we're getting into overall plant performance.

Small or poor-quality flowers can result from several factors, including plant genetics, inadequate light, water stress, nutrition, root restriction, extreme temperatures or general plant health.

Again, start with growing conditions.

If the plant looks weak overall, investigate why.

If it's healthy but the flowers aren't what you expected, check whether you're comparing it with highly edited photos, nursery-grown specimens or plants growing under completely different conditions.

The internet has given plants unrealistic beauty standards too.

Does mulch affect flowering?

Not directly in the way sunlight or plant maturity might, but good mulching can help create more stable root-zone conditions.

Mulch can help reduce moisture loss, moderate soil temperature and suppress some weed competition.

All of that can contribute to a healthier plant.

But mulch piled around the stem isn't better mulch.

Keep it over the soil and away from trunks, crowns and stems where appropriate.

The objective is happy roots.

Not burying the plant alive.

What if my flowering plant is in a pot?

Potted plants live in a much smaller world.

Their roots have limited access to water and nutrients, and potting mix can dry rapidly in warm weather.

Over time, plants can also become root-bound.

If a previously healthy flowering plant has been in the same pot for years and its performance has declined, look at the roots and growing media.

Does it need repotting?

Has the potting mix broken down?

Is water running straight through?

Is the plant drying out constantly?

Has it simply outgrown its accommodation?

Sometimes the plant doesn't need another fertiliser.

It needs a bigger house.

Why won't my native plant flower?

Start with exactly the same questions we'd ask about any other plant.

Is it mature enough?

Is it getting enough light?

Is it the correct flowering season?

Has it been pruned at the wrong time?

Is it healthy?

Is water appropriate?

Then look at the requirements of that particular species or cultivar.

“Natives” are not one group of plants with identical needs.

Australia contains rainforests, alpine environments, deserts, wetlands, coastal heath and everything in between.

A Callistemon and a native violet do not want the same life simply because both have an Australian passport.

Find out what that plant needs.

Why won't my Gardenia flower?

Gardenias are one of those plants that can make gardeners question every life decision they've ever made.

They generally perform best with good light, suitable moisture, appropriate nutrition and suitable soil conditions.

Too much shade can reduce flowering.

Water stress while buds are developing can contribute to bud drop.

And because Gardenias prefer acidic growing conditions, soil conditions can influence nutrient availability and overall performance.

But again, don't diagnose from one symptom.

Look at the whole plant.

Healthy foliage but no flowers?

Start with light and season.

Yellowing foliage as well?

Now soil conditions, roots and nutrition deserve closer attention.

Why won't my hedge flower?

First question:

How often are you cutting it?

😂

If you're constantly trimming a flowering hedge into perfect geometric submission, you may be removing flowering growth before it gets the opportunity to flower.

This doesn't mean you can't have a neat flowering hedge.

It means pruning timing matters.

Know when the plant flowers and what growth it flowers on, then plan major pruning accordingly.

Sometimes the hedge isn't refusing to flower.

You are extremely efficiently removing every attempt it makes.

And sometimes… the plant is just doing exactly what it was bred to do

This matters enormously with modern plant varieties.

Two cultivars of the same species can behave very differently.

One may flower more heavily.

One may be more compact.

One may have been selected primarily for foliage.

One may have a different flowering season or habit.

This is why knowing the actual variety name matters.

“Dianella.”

“Westringia.”

“Lomandra.”

“Callistemon.”

Those names only get you part of the way.

Cultivars are selected for particular characteristics, and those characteristics can completely change how useful the plant is in a garden.

Buy the plant for the job you actually need it to do.

Before you buy anything to make your plant flower, check these things

Start with sunlight.

Then ask when the plant is actually supposed to flower.

Check whether it's mature enough.

Think about when it was last pruned.

Look at the type of growth it flowers on.

Check soil moisture.

Look for pests or damaged buds.

Consider whether the weather has been unusual.

Look at what you've been fertilising it with.

And only then decide whether nutrition actually needs correcting.

Because there is no single bottle on a nursery shelf labelled:

MAKE STUBBORN PLANT FLOWER.

Believe me.

We'd sell heaps of it.

The biggest flowering mistake gardeners make

We tend to think flowers are the plant's reward to us for keeping it alive.

They're not.

Flowers are reproduction.

Once you understand that, a lot of seemingly strange plant behaviour starts making sense.

A plant needs enough energy.

It may need to reach maturity.

It may need the right temperature.

It may be responding to day length.

It may need the right season.

And it needs conditions that allow it to invest resources in reproduction rather than simply surviving.

So if your plant isn't flowering, don't immediately ask:

“What can I put on it?”

Ask:

“What is stopping this plant from doing what it naturally wants to do?”

That question will get you much closer to the answer.

And occasionally the answer really is:

Nothing.

Put the fertiliser down.

Stop staring at it.

And give the poor thing until spring.