Pick a palette of late- or long-blooming perennials, keeping your view colourful well into fall. Bonus: you can plant them now.
For most gardeners, our big “colour season” is late spring through summer, when we have a profusion of perennials, annuals, and hopefully some interesting shrubs and trees providing a rich tapestry of hues.
I’ve written a fair bit about supplementing bloom colour with intriguing foliage colour and textures in all types of plants.
This time, however, my thoughts turn to perennial all-stars: those that extend the blossom season either because they flower continuously or rebloom after a bit of a rest, or those that bloom late, coming into their own as the temperatures soar in late July through August, and into September.
The long bloomers. Many perennials have a long season of bloom, continuously producing flowers until something triggers them to stop. Some plants require deadheading (spent flowers being removed) to keep blooming, in the same way as we deadhead annual plants to keep them producing new flowers. Other perennials will simply keep on flowering with or without deadheading.
In my garden, the longest-blooming award goes to a petite relative of bleeding heart, the yellow corydalis (Corydalis lutea). This is an ideal plant for the front of a border or a rockery where you’re growing a number of low-growing, slow-spreading plants such as alpines. Yellow corydalis has lovely, fern-like foliage, and begins to flower for me in early- to mid-May. It doesn’t quit until a hard frost or snowfall shuts it down in late autumn. I wish some of the other species, like the blue-flowered C. elata, would bloom for months instead of just six weeks.
Daylily (Hemerocallis) breeders have made great advances with hybrids in recent years, developing cultivars that put out huge numbers of flower scapes and buds, as well as some that are continuous bloomers. I adore daylilies for their vast variety of colours, sizes and flower forms, and enjoy flower displays from early July until October. Last year I took a photo of the locally bred ‘Pride of Canning’ with frosty buds on November 30. That was definitely a record in my garden.
How do you know whether you need to deadhead perennials to promote new bloom? In some cases, you can’t know without experience, because not all species in a particular genus will rebloom. Campanulas, the bellflowers, are a great example: the peach-leaf bellflower (C. persicifolia) will keep flowering if you deadhead the spent flower stalks, while its relative the great bellflower (C. latifolia) blooms once and then is done. Regardless of whether plants rebloom or not, removing spent flowers is a good way to keep the garden tidy, and can help reduce fungal disease spread.
The late bloomers. It must be said that not every garden has things in bloom at the same time—we all have different conditions. My neighbour Jerry’s garden, a scant five kilometres away, is routinely a week or two ahead of my garden because his is sheltered from some of the winds that tend to blast my property. As a general rule, the plants included as late bloomers don’t start to flower until late July, early August—or even later.
The great thing about late-blooming perennials is that you can usually find them still for sale at nurseries during high summer. In fact, some nurseries may bring in late-blooming selections after the earlier bloomers and annuals have been sold off.
Contrary to what you might believe, you can plant perennials (and anything else) throughout the summer and well into autumn—there’s no need to stop planting just because the big box stores have closed up shop by the end of June. I continue to plant, divide, transplant, move and otherwise dig around in my garden throughout the summer and autumn, finally shifting into bulb-planting mode in mid-October.
The main thing to remember about planting during summer months is to do so on overcast days so you don’t stress or shock plants; mulch them and keep them well watered while they settle into their new home.
Some of the late bloomers have very attractive foliage, which makes them lovely to look at long before they come into flower.
Perhaps the best example of this is the black cohosh, Actaea (renamed from but still sometimes labelled as Cimicifuga). It has gorgeous foliage something like that of a fern or an astilbe, and most varieties have purple to near-black foliage. The tall spikes of white or pink-tinged flowers don’t appear until mid-late August in my garden, and last for weeks, leaving behind elegant seedheads that withstand the elements throughout winter.
11 best-bet long bloomers
- Achillea: Yarrow is best suited to a well-draining location; its clustered flowers—in shades of pink, yellow, orange, red and gold—are attractive to pollinators.
- Agastache: Hyssop is a mint relative with spiky purple or pink flowers. ‘Golden Jubilee’ has gold foliage. Make sure to select hardy varieties—there are also annual types.
- Asclepias: The milkweeds have clusters of brightly coloured flowers, and are beloved by monarch butterflies.
- Astrantia: Masterwort has been an underused perennial, but is becoming popular for its delightful starry flowers and reblooming habit. Look for ‘Ruby Wedding’ and ‘Star of Heaven.’
- Campanula: Most bellflowers have a long period of bloom, whether or not they rebloom after deadheading.
- Dianthus: Many of the pinks and carnations will bloom for several months, especially with deadheading.
- Echinacea: Coneflower blossoms each last for many weeks, and if you deadhead the spent flowers the plants just keep producing more until cold weather.
- Eryngium: Sea hollies produce blue, green, purple or silver cones of flowers surrounded with a ruff of bracts that hold their colour for many weeks. ‘Jade Frost’ has green and white foliage with pink tints in its new growth.
- Euphorbia: There are dozens of different euphorbias, each with colourful bracts surrounding the flowers (think of poinsettias). Some are clump formers while others spread: check labels for growth habit, as well as zone hardiness.
- Nepeta: Catmints tend to be resistant to deer, and they attract pollinators. Deadhead to keep plants blooming well into autumn.
- Scabiosa and Knautia: Two different genera are known as pincushion flowers; deadheading will keep them producing into autumn.
10 late-blooming beauties
- Actaea: Black cohosh is personal favourite for its elegant burgundy foliage as well as its fragrant flower spikes. Look for ‘Black Negligee,’ ‘Pink Spike’ and ‘Hillside Black Beauty.’
- Aster: The fall-blooming perennial asters range from low-growing mounding types to tall forms suited for the back of the border. Excellent for cutting and for attracting pollinators.
- Chelone: Turtlehead is native to North America, and prefers a moist location. Bees love the flowers, and the seedheads will stand overwinter.
- Eupatorium: Joe-pye weed is native and a great pollinator plant. New dwarf forms such as ‘Little Joe’ are now available for those with small gardens. ‘Chocolate’ has purple-green foliage and white flowers, and is the last perennial to bloom in my garden.
- Gentian: Look for willow gentian (Gentiana asclepiadea), a large, almost shrub-like perennial with blue to purple flowers; it’s probably the easiest of the gentians to grow.
- Helenium: Helen’s flower resembles an aster but comes in autumn shades of rust, yellow, orange and bronze. Formerly only tall types were available, but short forms, less than three feet, are now widely sold.
- Kirengoshoma: Yellow waxy-bells are simply gorgeous; well suited for a woodland, shady garden.
- Perovskia: Russian sage must have excellent drainage to overwinter. It is deer-resistant with lavender-like spikes of purple flowers and grey-green foliage.
- Sedum: Usually tall sedums, such as ‘Autumn Joy’ and ‘Postman’s Pride,’ are late-blooming types, but there’s an excellent low-growing form called ‘October Daphne’ that I highly recommend.
- Vernonia: Another native—and not to be confused with Veronica—ironweed is a tall, clump-forming plant with fuchsia or magenta flowers. Excellent to plant in meadows and to attract pollinators.