If you’re wondering when to plant canna lilies in Ontario, timing is everything for these tropical showstoppers. Getting them in the ground at the right moment ensures a summer full of vibrant color and lush foliage.
This guide gives you the clear, practical advice you need for success. We’ll cover the optimal spring window, how to prepare, and tips for a fantastic display.
When to Plant Canna Lilies in Ontario
The short answer is to plant your canna lily rhizomes in late spring, after all danger of frost has passed. Canna lilies are tender perennials, meaning they cannot survive freezing temperatures. Planting too early risks rot or cold damage.
For most of Ontario, the safe planting period is from late May to early June. You should always use your local last frost date as your primary guide. A good rule is to plant your cannas at the same time you would plant tomatoes or other heat-loving annuals outdoors.
Understanding Your Local Frost Dates
Your local last frost date is the single most important factor. This date varies across Ontario’s different climate zones.
- Southern Ontario & the GTA: Last frost typically falls between May 5th and May 15th. Aim to plant from mid to late May.
- Eastern Ontario (Ottawa region): Last frost is often around May 10th-15th. Late May planting is safest.
- Southwestern Ontario: This region warms up a bit earlier. Planting in early to mid-May can sometimes be possible, but watch the forecast.
- Central & Northern Ontario: Frost dates are later, often extending into early June. Wait until early to mid-June to be sure.
When in doubt, wait another week. Cannas will catch up quickly in warm soil.
The Importance of Soil Temperature
Frost isn’t the only concern. Cannas need warm soil to wake up and start growing. Cold, wet soil can cause the rhizomes to rot before they even sprout.
Aim for a consistent soil temperature of at least 15°C (60°F). You can use a simple soil thermometer to check. If you don’t have one, a general indicator is when the soil feels comfortably warm to the touch, not cold and clammy.
Getting a Head Start: Pre-Sprouting Indoors
For earlier blooms and stronger plants, many Ontario gardeners pre-sprout their canna rhizomes indoors. This process gives them a 4-6 week head start on the season.
- Timing: Start this process about a month before your expected outdoor planting date, usually in mid to late April.
- Containers: Use pots or trays that are at least 15-20 cm deep. Fill them with a moist, well-draining potting mix.
- Planting: Place the rhizomes horizontally, with any eyes or pink growth points facing up. Cover them with about 5 cm of soil.
- Care: Put the pots in a warm, sunny location like a south-facing window. Water sparingly until you see growth, then keep the soil consistently moist.
By the time it’s warm enough outside, you’ll have sturdy young plants ready to take off.
Step-by-Step Outdoor Planting Guide
When the weather and soil are finally ready, follow these steps for planting your cannas in the garden.
1. Choosing and Preparing the Site
Cannas love full sun. Choose a spot that gets at least 6-8 hours of direct sunlight daily. They also prefer rich, moist soil. Work in plenty of compost or well-rotted manure a few weeks before planting to improve fertility and drainage.
2. Planting the Rhizomes or Pre-Sprouted Plants
- Dig a hole about 10-15 cm deep.
- For rhizomes: Place them with the eyes facing up. For pre-sprouted plants: plant them at the same depth they were in their pot.
- Space rhizomes or plants about 30-60 cm apart, depending on the variety’s mature size.
- Backfill the hole and gently firm the soil around it.
- Water thoroughly after planting to settle the soil.
3. Initial Care After Planting
Keep the soil consistently moist as your cannas establish themselves. Applying a layer of mulch around the plants helps retain moisture, suppress weeds, and keep the soil warm. A balanced, slow-release fertilizer can be mixed into the soil at planting time to provide nutrients.
Caring for Your Canna Lilies Through the Season
Once established, cannas are relatively low-maintenance but do benefit from regular care.
- Watering: Cannas are thirsty plants. Water deeply at least once a week, more often during hot, dry spells.
- Fertilizing: Feed them monthly with a balanced liquid fertilizer or a fertilizer higher in phosphorus to promote blooming.
- Deadheading: Remove spent flower stalks to encourage more blooms to form and keep the plant looking tidy.
- Pest Watch: Keep an eye out for Japanese beetles and caterpillars, which can chew on the leaves. Hand-picking is often effective for small infestations.
What to Do With Cannas in Fall
Since cannas are not winter-hardy in Ontario, you must dig up the rhizomes after the first fall frost blackens the foliage.
- Cut the stems back to about 10-15 cm.
- Carefully dig up the clump of rhizomes, trying not to damage them.
- Shake off excess soil and let them dry in a cool, airy place for a day or two.
- Store them in a box or crate filled with slightly moist peat moss, vermiculite, or wood shavings.
- Place the box in a cool, dark location where temperatures stay between 5-10°C (40-50°F), like a basement or garage.
Check on them occasionally through the winter to ensure they are not drying out completely or rotting.
Common Questions About Growing Cannas in Ontario
Can I leave canna lilies in the ground over winter in Ontario?
No, it is not recommended. The ground freezes too deeply, and the rhizomes will not survive. You must dig them up for winter storage.
My cannas aren’t blooming. What’s wrong?
The most common reasons are not enough sun, overcrowded rhizomes, or insufficient nutrients. Ensure they get full sun, divide clumps every 3-4 years, and fertilize regularly during the growing season.
When is it too late to plant canna lilies?
You can plant them through early summer, but planting after late June may not give them enough time to establish and produce a good show of flowers before fall frost arrives. Earlier is always better.
Can I grow cannas in containers?
Absolutely! They make excellent thriller plants for large pots. Use a big container with drainage holes, quality potting mix, and water even more frequently, as containers dry out fast. You’ll still need to store the rhizomes indoors over winter.
Do deer eat canna lilies?
Fortunately, cannas are generally considered deer-resistant. The thick, fibrous foliage is not their preferred food, making cannas a good choice for gardens where deer are a problem.
With the right timing and care, canna lilies will bring a spectacular tropical flair to your Ontario garden. By waiting for warm soil in late spring, giving them sun and water, and remembering to store them in the fall, you’ll enjoy their bold beauty for many seasons to come.