1. Garden Mums (Chrysanthemum morifolium)
Frost tolerance: Hardy to approximately minus 5 degrees Celsius when established
Bloom duration: Six to eight weeks from purchase through to hard frost
Best for: Garden beds, large containers, front porch displays
Garden mums are the undisputed star of the Ontario fall garden and the plant most synonymous with autumn colour across the GTA. Their densely packed flower heads in shades of deep burgundy, burnt orange, golden yellow, rich purple, and pure white are the visual definition of fall, and they bloom prolifically from September right through to the first hard frosts of October and sometimes beyond.
Walk into any garden centre in Ontario in September, and mums will be everywhere, and for good reason. They are reliable, abundant, immediately impactful, and available in a colour range that pairs beautifully with the warm tones of fall foliage and seasonal décor. A cluster of three mums in complementary colours planted in a large container by your front door transforms the entire entrance of your home in minutes.
The perennial question everyone asks:
Garden mums are technically perennial, but their performance as perennials in Zone 6a Ontario is inconsistent at best. The mums sold at garden centres in September have been forced into bloom in greenhouse conditions, and their root systems are often underdeveloped for reliable overwintering in our cold climate. Some will return the following spring. Many will not. Rather than being disappointed, treat fall mums as you would a long-blooming seasonal annual and enjoy them for the six to eight weeks of spectacular colour they reliably deliver before frost ends the season.
For genuinely perennial mum performance in Zone 6a, look for hardy garden mums specifically labelled as perennial or cold-hardy varieties, plant them in spring rather than fall to give roots a full growing season to establish, and mulch heavily before winter.
Design tip:
Plant mums in odd-numbered groupings of three or five for the most natural and visually impactful display. Combine deep burgundy and golden yellow for a classic fall colour pairing, or use all-white mums for a clean, contemporary fall look that works beautifully with dark containers and seasonal pumpkin décor.
2. Pansies and Violas (Viola wittrockiana and Viola cornuta)
Frost tolerance: Hardy to minus 8 to minus 10 degrees Celsius, survives light snow
Bloom duration: September through November and again in early spring
Best for: Containers, window boxes, front borders, hanging baskets
If garden mums are the star of the fall garden, pansies are the quietly extraordinary supporting cast that outlast almost everything else in the October and November garden. They are among the most cold-hardy flowering plants available for Ontario fall gardens, tolerating temperatures as low as minus 8 to minus 10 degrees Celsius with ease and bouncing back from light snow and frost that would devastate any other annual flowering plant.
Fall planted pansies do something genuinely remarkable in Zone 6a: they go semi-dormant through the coldest weeks of winter and then re-emerge and bloom again in early spring, often appearing while snow is still on the ground in March and April, weeks before any other spring flower makes an appearance. A single planting of fall pansies gives you colour in October, November, March, and April from one investment, making them one of the best value fall plants available.
Violas are smaller-flowered cousins of pansies with an even more prolific blooming habit and slightly better cold tolerance. They work beautifully as a spillover plant in fall containers, tumbling over the edges of pots and window boxes with a froth of small, cheerful flowers in purples, yellows, and whites.
Fall container design with pansies:
Replace your tired summer spillers with violas as the trailing element in your fall container displays. Combine with ornamental kale as the thriller, pansies as the filler, and you have an elegant, completely frost-hardy fall container that will look beautiful well into November.
Design tip:
Choose pansies in the deep jewel tones of fall, midnight purple, deep burgundy, rich violet, and golden yellow, rather than the pastel shades better suited to spring displays. Fall jewel toned pansies paired with ornamental kale and mums create a sophisticated and cohesive fall colour story that looks intentional and designed rather than simply assembled.
3. Ornamental Kale and Cabbage (Brassica oleracea)
Frost tolerance: Hardy to minus 10 degrees Celsius, colour improves with frost
Bloom duration: September through November, often beyond first frost
Best for: Containers, window boxes, front borders, mixed fall displays
Ornamental kale and cabbage are the unsung heroes of the fall container garden and one of the most frost-tolerant flowering plants available for Zone 6a Ontario displays. Their dramatic rosettes of ruffled leaves in combinations of deep purple, pink, white, and green create a bold, architectural focal point in fall containers and garden beds that no flowering plant can quite replicate.
What makes ornamental kale genuinely special for Ontario fall gardening is its relationship with cold. Unlike most plants that decline as temperatures drop, ornamental kale and cabbage actually become more vivid and more beautiful as nights cool and frost arrives. The cold intensifies the central colour of the rosette, deepening purples and brightening pinks in a way that makes a frosted kale plant in late October look more spectacular than the same plant did in warm September conditions.
They are genuinely among the last plants standing in the fall Ontario garden, often looking beautiful well into November and sometimes beyond, long after mums and most other fall flowers have succumbed to hard frost.
Using ornamental kale as your thriller:
Ornamental kale is the perfect thriller plant for fall containers using the thriller filler spiller method. A tall, dramatic kale rosette in the centre or back of a pot, surrounded by pansies or violas as fillers and trailing ivy or sweet alyssum as spillers, creates a complete, professionally designed fall container that requires no further attention until hard frost ends the season.
Design tip:
Mix purple-centred and white-centred ornamental kale varieties in the same container or bed for a striking two-tone effect. The contrast between deep purple and clean white against the backdrop of green outer leaves is one of the most elegant colour combinations available in the fall garden.
4. New England Aster (Symphyotrichum novae-angliae)
Frost tolerance: Hardy to minus 15 degrees Celsius, fully perennial in Zone 6a
Bloom duration: September through October
Best for: Garden beds, back of border, naturalistic plantings
The New England aster deserves a dedicated place in every Ontario fall garden for reasons that go well beyond its beauty. As a native Ontario plant, it has evolved alongside local pollinators for thousands of years, and the nectar it provides in September and October is genuinely critical food for monarch butterflies, native bumblebees, and honey bees building their winter reserves before the cold arrives. Planting New England aster is not just a garden design choice. It is an act of genuine ecological support for the local pollinator community at exactly the moment they need it most.
The flowers themselves are stunning. Rich purple, violet, deep pink, and white daisy-like blooms with golden yellow centres cover the plant in September and October in a display that is far more spectacular than its quiet green presence through summer would suggest. Plants that looked unremarkable through July and August suddenly transform into one of the most beautiful things in the fall garden.
Unlike garden mums, the New England aster is genuinely and reliably perennial in Zone 6a Ontario, returning every spring and growing larger and more floriferous with each passing year. It is a long-term investment in fall colour that requires no annual repurchasing and improves automatically with time.
Managing height in the garden:
New England aster can reach 90 to 120 centimetres in height if left unpinched, which can look spectacular in a naturalistic or cottage garden but may be too tall for a formal border. Pinch plants back by one third in late June to encourage bushier, more compact growth with more but smaller flower heads through September and October.
Design tip:
Combine New England aster with ornamental grasses and autumn sedum for a naturalistic fall display that looks beautiful, requires minimal maintenance, and provides extraordinary wildlife value through the most important weeks of the migration and overwintering season.
5. Witch Hazel (Hamamelis virginiana)
Frost tolerance: Fully hardy to minus 25 degrees Celsius, Zone 6a reliable
Bloom duration: October through December, sometimes into January
Best for: Garden borders, specimen planting, woodland gardens
Witch hazel is the most unexpected and genuinely extraordinary entry on this list and the plant that will make every visitor to your fall and early winter garden stop and stare. Virginia witch hazel, the native North American species, blooms in October through December, often flowering after every other plant in the garden has gone dormant for the year. Its spidery, fragrant yellow flowers appear directly on bare branches after the leaves have fallen, creating a bloom display of remarkable delicacy and beauty at a time when most gardeners have completely given up on flowers until May.
It is not a container plant and it is not a quick-impact seasonal purchase. Witch hazel is a large shrub or small tree that takes several years to establish and flower freely. But as a long-term investment in year-round garden interest, particularly for that difficult late fall and early winter window when nothing else is blooming in a Zone 6a Ontario garden, it is unmatched.
Virginia witch hazel is native to Ontario's woodlands and perfectly adapted to our climate and growing conditions. It tolerates partial shade beautifully, making it an excellent choice for the challenging shaded areas of a GTA garden where other flowering shrubs struggle. Its fall foliage turns brilliant yellow and orange before dropping to reveal the flowers developing underneath.
For more immediate impact:
Hybrid witch hazels like Arnold Promise and Diane produce larger, more colourful flowers than the native species and bloom in late winter and very early spring, often in February and March, rather than fall. Both are excellent choices for Zone 6a and provide bloom at a time when the garden desperately needs it.
Design tip:
Plant witch hazel as a specimen in a location visible from indoors, near a window or glass door, so you can appreciate its late season bloom from the warmth of your home on the cold October and November days when venturing outside to admire it feels less appealing.
Building a Fall Container Display That Lasts
The most effective fall containers combine plants from different categories on this list to create displays with maximum frost tolerance, visual impact, and longevity through the full Ontario fall season.
A simple and stunning fall container formula uses the thriller filler spiller structure with fall-specific plants. Place an ornamental kale or tall mum as your thriller in the centre or back of a large container. Surround it with pansies or violas as your filler, choosing colours that complement or intentionally contrast the thriller. Add trailing ivy, creeping wire vine, or sweet alyssum as your spiller to cascade over the container edge and soften the hard lines of the pot.
This combination gives you a container that is largely frost-hardy, continuously beautiful through September and October, and requires nothing more than occasional watering to maintain through the fall season.
Refresh rather than replace:
If your summer containers still have viable structural elements like a healthy thriller plant or attractive trailing foliage, you do not need to start from scratch. Simply remove the tired summer annuals, refresh the top layer of potting mix with fresh compost, and add fall plants around the existing structure. This approach saves money, reduces waste, and often produces more interesting and layered results than starting with an empty pot.
Embrace the Fall Garden
The Ontario fall garden is one of the most beautiful and most underappreciated seasons in the gardening year. The combination of golden light, crisp air, and the rich warm colour palette of autumn creates a garden atmosphere that is entirely distinct from summer and in many ways more beautiful and more emotionally resonant.
Stop by Lakeside Garden Gallery this September and let our team help you choose the right fall flowers, containers, and seasonal décor to keep your garden looking spectacular right through to November. Our fall selection arrives fresh throughout September and October so there is always something new and beautiful to discover. 🍂🌸🌿