It depends on the bulb. Hardy summer bloomers, especially true lilies, can go in the ground this fall. Tender ones like dahlias, gladiolus and cannas can’t. They’d freeze over winter, so they wait until spring.
I get this question every September, usually from someone standing in a garden centre holding a bag of bulbs on clearance. Fall is bulb season, so it’s easy to assume everything goes in the ground. It doesn’t. Getting it wrong costs you money and a summer of flowers, so let me sort out which is which.
Hardy vs. Tender: The Difference That Decides Everything
The only question that matters is whether the plant can survive an Ontario winter in the ground.
- Hardy bulbs handle freezing soil. They actually need the cold. Tulips and daffodils are the classic examples, and so are true lilies and alliums.
- Tender bulbs come from warm climates and get killed by frost. Gardeners plant them in late spring, after the danger of frost has passed.
Here’s the catch. A lot of these “bulbs” aren’t technically bulbs. Dahlias grow from tubers, gladiolus from corms, and cannas from rhizomes. Gardeners call them all bulbs for simplicity, and I’ll do the same, but the structure matters when it comes to storing them.
| Summer bloomer | Type | Plant in fall in Ontario? |
|---|---|---|
| Asiatic, Oriental, Martagon lilies | True bulb, hardy | Yes |
| Alliums | True bulb, hardy | Yes |
| Dahlias | Tuber, tender | No, plant in spring |
| Gladiolus | Corm, tender | No, plant in spring |
| Cannas | Rhizome, tender | No, plant in spring |
| Tuberous begonias | Tuber, tender | No, plant in spring |
| Caladiums, calla lilies, elephant ears | Tender | No, plant in spring |
Even the milder corners of the province, like Niagara and Windsor, are too cold for most tender bulbs to overwinter reliably. Those plants generally survive outdoors only in much warmer zones, which is why northern gardeners dig them up every fall.
The Summer Bulbs You Can Plant Now
True Lilies: My Top Pick for Fall
If you want summer flowers from a fall planting, plant lilies. Fall is one of the best times to plant them, and extension services recommend it because the bulbs get a long stretch to develop roots before they send up a flower stalk. Mid-September through October is the usual window, which makes right now a good time in most of southern Ontario.
A few lily types to look for:
- Asiatic lilies: the earliest to bloom, very hardy, and the easiest to grow. Lots of colours, little scent.
- Oriental lilies: later blooming and strongly fragrant. Gorgeous, but fussier. They like slightly acidic, well-drained soil and a mulch in fall.
- Martagon lilies: they’ll tolerate shade, with nodding flowers and swept-back petals.
A quick warning about names. Daylilies, calla lilies, canna lilies and lily-of-the-valley aren’t true lilies (genus Lilium). I mention it because it trips up plenty of shoppers.
How to Plant Lily Bulbs
Lilies are less forgiving than tulips in one way: they never go fully dormant. That means the bulbs shouldn’t dry out, so get them in the ground soon after you buy them.
- Pick a sunny spot. Aim for six to eight hours of sun. Too much shade makes lilies tall and floppy. Martagons are the exception.
- Make sure the soil drains. Lily bulbs rot in wet ground. Mix compost into heavy clay.
- Plant deep enough. Large bulbs go about 4 to 6 inches deep, smaller ones 2 to 4 inches, measured from the top of the bulb. A common rule is three times the bulb’s diameter.
- Group them. Plant in threes or fives, roughly 8 to 12 inches apart, for a fuller display.
- Water at the base in the morning, not on the leaves, which helps prevent botrytis blight.
- Mulch after the ground starts to cool, especially for Oriental types.
A Trick I Love: Layering Lilies With Spring Bulbs
Since you’re already planting bulbs this month, try a “lasagna” planting. Plant the lily bulbs at their proper depth, cover them with 2 to 4 inches of soil, and then plant your tulips or daffodils on top. The spring bulbs bloom first, the lilies follow in summer, and you get two seasons from one bed.
Alliums
Alliums are ornamental onion relatives that bloom in a big round globe of tiny flowers. They’re fall-planted and fully hardy. Many bloom in late spring and carry on into early summer, so they bridge the gap between spring bulbs and summer flowers. Plant them in October, like your daffodils.
The Summer Bulbs You Should NOT Plant Now
Please don’t put dahlias, gladiolus, cannas, tuberous begonias, caladiums or calla lilies in the ground this fall. They aren’t hardy, and one hard freeze will turn them to mush.
I know they’re often sold in fall at a discount, and it’s tempting. If you buy them, treat them as next year’s plants. Keep them cool, dry and frost-free over winter, then plant them after your last frost. And if you find them for sale in spring garden centres at full price, don’t feel bad about waiting to buy then either. The bulbs are the same, and you’ll be planting them at the right time.
What to Do This Fall Instead: Dig and Store Your Tender Bulbs
If you already grow dahlias, glads or cannas, this is the time to lift them. Overwintering your own saves real money, especially for named dahlia varieties. The basic sequence looks like this:
- Wait for frost to blacken the tops, but dig before the ground freezes.
- Loosen the soil several inches from the plant with a fork. Don’t stab the tubers. Wounds let rot in.
- Cut back the foliage. Dahlias go down to a few inches. Glads to about an inch.
- Cure them. Let dahlias, cannas and caladiums dry for a day to a few days. Gladiolus corms need about three weeks, and you shouldn’t wash them, since moisture rots them.
- Store cool and dark, around 40 to 50°F (5 to 10°C), packed in peat moss, vermiculite or sand.
- Pick a spot that stays above freezing, like a cool basement. A garage or attic can freeze.
- Label everything, so you’re not guessing in May.
- Check them through winter and toss any that shrivel or rot.
When to Plant Tender Summer Bulbs in Ontario
Plant them after your last frost. That’s typically early to mid-May in much of southern Ontario, with later dates in the north. Averages for London and Ottawa fall in the first ten days of May, and Toronto’s run a little later. Many gardeners wait until mid to late May to be safe. If you’d like a head start, you can pot up dahlias and cannas indoors a few weeks earlier and move them out once the weather settles.
Quick Questions I Get Asked
Can I plant dahlia tubers in fall in Ontario? No. They aren’t hardy here, and they’ll rot or freeze. Store them and plant in spring.
Is fall or spring better for lilies? Fall is usually preferred, because the roots get more time to develop. Spring planting works too, as early as you can get the soil open.
Can I plant gladiolus in October? No. Plant them in spring after frost, and dig the corms up in fall.
What if the lily bulbs I bought have been sitting in a bag? Plant them right away. Unlike tulips, lily bulbs don’t fully dry out, so don’t leave them waiting.
Can I still plant summer bulbs in a pot? For lilies, yes, though potted bulbs face harsher winter cold than ones in the ground. Tender bulbs should stay indoors.
My Take
If I could plant only one summer-flowering bulb this fall, it would be a lily. It’s hardy, it’s rewarding, and the timing is right in the next few weeks. Add some alliums for the transition, tuck a few spring bulbs above them, and you’ve got colour from April through August.
And for those tender beauties like dahlias and glads, just be patient. Save your energy this fall for digging and storing them, and they’ll reward you when the weather warms.
Are you planting lilies this year, or trying to overwinter dahlias? Tell me in the comments, and I’ll help you plan it out.
Suggested title tag: Can You Plant Summer-Flowering Bulbs in Fall in Ontario?
Meta description: Which summer-flowering bulbs can you plant now in Ontario? Lilies and alliums yes, dahlias and gladiolus no. Learn what to plant and what to store.
Sources and fact-check notes
- Lilies in fall: Nebraska Extension says lily bulbs can be planted in spring or fall, from about mid-September through October, with fall preferred because it allows a longer period for root development. It also gives depths of 4 to 6 inches for large bulbs and 2 to 4 inches for smaller ones, notes that lilies never fully go dormant, and recommends groupings 8 to 12 inches apart. Iowa State Extension gives the rule of three times the bulb’s diameter.
- Not true lilies: daylily, lily-of-the-valley and blackberry lily are separate plants from true lilies, and calla and canna lilies are the same. Asiatics are the hardiest and easiest, while Oriental lilies like organic, slightly acidic, well-drained soil and a fall mulch.
- Lasagna planting: a bulb supplier suggests planting lilies first, covering them with 2 to 4 inches of soil, then adding narcissi or tulips on top.
- Tender bulbs: dahlias, cannas, gladiolus, caladiums, calla lilies and tuberous begonias are tender and should be dug after frost but before the ground freezes. Store them cool, and don’t leave them where they might freeze, like an attic or garage. Gladiolus corms should not be washed and need about three weeks of curing.
- Spring planting: these plants go out in late spring after frost danger has passed. London and Ottawa’s average last frosts fall between May 1 and 10, Toronto’s between May 11 and 20.
- Alliums: one master gardener guide lists alliums among October-planted bulbs.
A few things to check before publishing: Ontario-specific dates for lilies (my sources are from the US Midwest, where the mid-September to October window fits southern Ontario reasonably well), and whether alliums bloom late enough to count as “summer” for your audience. I kept that claim modest on purpose.
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