Cool Flowers To Extend The Flowering Season

If you didn’t know any better, you might think that some of the best flowers only appear during summer for a brief window, and then the best of the flowering season for the whole year is finished.

Luckily, that’s not the case. While spring is often celebrated as a great relief for those of us who find joy and peace in our gardens, it’s fall and early spring where you can inject more color into your garden.

Yes, at that point most of the flowers in your garden are winding down, or they’re non-existent above the soil line, those which bring so much color and life into a summer garden, leaving behind too much space when they finish.

But by utilizing clever planting choices, you can extend the flowering season for much longer than you might think.

Here’s everything you need to know.

What You Probably Don’t Know About Annuals

Annuals can be divided into two categories: tender annuals, such as Tithonia (see also Flower Names Beginning With T), which don’t last in cold temperatures, and hardy annuals, or cool flowers, which do.

While you might associate annuals with summer, and filling the gaps between your perennial plants, there’s a lot to be said for planting annuals at other times of the year, specifically getting them to flower in autumn, or even very early spring.

If you do it right, you can ‘overwinter’ your annuals outside, but as to what annuals you can do this with depends on which zone you live in.

This is far from a new technique, we’ve largely just forgotten about it.

There’s something to be said for older ways, as things get more and more complicated with new techniques, sometimes the best way is one that isn’t broken.

As long as you meet the growing requirements for these hardy annuals, they will provide you with color for an extended season, and most will flower earlier than those planted at their normal time of year.

What Is A Cool Flower?

The term has nothing to do with street cred! Cool flowers are those which withstand cold temperatures that other plants would simply wither in.

Mostly annuals, cool flowers not only help to add color and interest into the bare spots in your garden, but they also sustain the pollinators, too.

It helps that these plants are easy to grow, and some of them can even tolerate a good snow shower!

The Best Time For Planting Cool Flowers In Your Garden

You may notice that those flowers you wait until summer to plant out, often stall their growth in the hottest months of the year.

Take calendulas, for example. Most of the time, people will start them off by sowing seeds, and then only transplanting them out once the weather stays reliably warm, and all risk of cold snaps are gone.

If you like keeping an eye on your garden, you may notice that their growth rate slows down when the weather gets balmy. 

This is because the calendula is a cool flower, and prefers cooler temperatures. So why not grow it earlier?

Cool flowers do best when planted in late winter and early spring.

While this might go against everything a seed packet may tell you, it makes sense once you understand why.

When you choose to plant cool flowers in the middle or later part of winter, you’re essentially planting them in spring, because they’ll start blooming around March and April, which can be considerably earlier than when you’re used to seeing them flower.

It’s important to note that you won’t see any growth until after the first frost, but the fact remains that you’re still planting cool flowers in spring.

And while you may think that you should wait until warmer weather before planting cool flowers, the truth is that you can plant them in cooler conditions, and they’ll grow and bloom in colder temperatures.

Different Ways Of Planting Your Cool Flowers

Sow The Seeds Directly Into Your Garden

If the seeds are particularly frost resistant, such as larkspur, cornflowers, or poppies, you can sow them straight into the ground during fall.

Make sure to free the border or bed of weeds and dead plant matter. Using a trowel or a fork, turn over the soil a little and smooth the top of the bed. 

Sow seeds according to the packet instructions, and cover the seeds lightly.

If you prefer, you can also do this during the first few weeks of spring, at the first opportunity when the soil is warm enough to work with.

You can also sow the seeds in succession, so that you have weeks of color to enjoy.

Sow The Seeds Inside

You don’t need a greenhouse for this if you don’t have one. A sunny windowsill, or even a table with a grow light on top will work just fine for starting seeds off in winter.

Sow the seeds how the seed packet advises, using potting soil and either a tray or a plug tray, or individual pots. Keep them moist and warm, somewhere light.

Let them grow on, repotting them when they have at least one set of true leaves.

Don’t take them outside until they have two sets of true leaves, and are at least a couple of inches in height.

Then you can move them outdoors in early spring, but make sure you acclimate them gradually. 

You can do this by placing them outside for a few hours, extending the time each day, and this will stop them from getting shocked.  

Why You Shouldn’t Worry About The State Of The Subsoil In Your Garden

Some that talk about sowing cold annuals suggest that you need to improve the subsoil within your garden to improve it, and therefore improve the health of your plants.

Some guides go so far as to talk about the deep soil, which you only need to worry about if your garden is, in a nutshell: unworkable. 

If your soil is too boggy, or it has gotten compacted to the point of being harder than rock, this is when you should concern yourself with it.

Otherwise, mulch the top 8 inches of the soil. You can do this by adding a generous layer of fresh compost around your plants each year (which they will appreciate anyway), treating your garden one bed at a time.

This shouldn’t be a job you should expect to complete overnight.

You should aim to treat at this depth because nearly the entirety of the plants you’ll grow in your garden will root at this depth, and the aerobic bacteria in the soil are more prevalent at this level.

All of this goodness will encourage the right microbes to work, and inject a good amount of nutrition into the earth.

This will eventually help the deeper parts of the soil, too, which means you don’t need to worry about any further than that.

How To Choose Cool Flowers

One of the best ways to choose cool flowers is to simply select what you know grows in your garden.

If you don’t know that yet, your hardiness zone will give you a good idea of what will survive in your area, especially when temperatures drop and weather conditions are less than ideal.

It’s a great starting point, but it’s interesting to know that flowers that may not be suitable for your zone on paper can work really well anyway.

So select a mixture. Go for plenty of cool flowers which are pretty much guaranteed to work in your area, as well as trying a few plants that might not. Nature can surprise you. 

Cool Flowers And Cold Hardy Plants To Grow In Your Garden

To help get you started on extending the flowering season within your garden, here are a selection of plants which work well when treated as cool flowers.


Perhaps the most famous of the fall-blooming plants is the aster. Most asters will flower from late summer, well into autumn as long as the frosts don’t get too severe.

They love full sunlight for as long as possible, so make sure you choose a position in your garden with plenty of light. 

Depending on the type you go for, asters can range between a foot tall and 6 feet tall, spreading anywhere from a foot to 3 feet wide.

Asters bloom in different colors, including white, blue, purple, and pink, which is dictated by the variety.

They also help sustain pollinators this far into the season, when nectar and other food sources become scarce. 


Another staple of fall to winter gardening is the chrysanthemum. The height is dictated by the type, so they may reach anything between 1 and 3 feet tall, as long as they are grown in full sunlight.

They tolerate light frosts, and there are plenty of colors to select from. You can also choose to grow them as annual plants, making the chrysanthemum a cool flower candidate.

Nigella damascena ‘Love-In-A-Mist’

Also known as devil in the bush, Nigella (see also Nigella Grow Guide) is a fascinating annual which produces airy, feathery foliage, and some of the most striking flowers you can grow in your garden.

The flowers are available in pastel shades of blue, white, pink, and purple. They’re perfect for attracting butterflies and bees, and even hummingbirds if you live somewhere that has those!

The plant is easy to grow, tolerating both shade and sun, and blooms all through the year. It’s an excellent choice for cooler gardens, as it prefers cooler weather.

With Nigella flowers, you can sow the seeds directly into the soil, and normally, you’d sow them between March and June for summer flowers.

For earlier flowers, treat it as a cool flower, sowing seeds in September.

This will give the plants enough time to establish themselves before the frosts, and they will flower much earlier the following year.

Centaurea cyanus ‘Cornflower’

Absolutely adored by bees, this plant is endangered in the wild, thanks to intensive agricultural farming. 

This plant produces very delicate-looking blooms in many shades, and you can sow seeds in either late spring, for summer color, or early fall, for early spring color.

Cornflowers are very easy to grow, and only need the occasional watering and a bright position to produce fantastic flowers.

To extend the blooming period even longer, deadhead spent flowers. 

Calendula officinalis ‘Pot Marigold’

Also known as the Scotch marigold, or the pot marigold, this plant produces daisy-like flowers in shades of yellow and orange.

They’re one of the easiest plants to grow, racing to grow flowers in as little as two months after sowing.

Full sunlight and nutrient-rich, well-draining soil is a must, however. It’s also worth knowing that they don’t like extreme temperatures, either cold or hot, so you may want to start off these beautiful plants indoors.

Final Thoughts

While treating cool annuals differently to perhaps you’re used to will be strange at first, it will considerably open up the flowering window, and both the colors and flowers available to you in the planting season.

It will also help provide plenty of food for the pollinators, as well as attracting beneficial insects into your garden, so there aren’t any downsides to planting cold-hardy annuals or cool flowers outside of the season you’re used to.

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