Canna lilies (Canna spp.) are striking tropicals that put on a fantastic summer show with bold flower spikes producing large, ruffled blooms in shades of orange, red, yellow, and white, highly attractive to pollinators like hummingbirds.
They’re grown as annuals or perennials, depending on your region, and the handsome foliage is truly spectacular, with large paddle-like leaves in shades of chartreuse, copper, cream, green, pink, and scarlet – and some varieties even sport elegant striping!
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But foliage alone is only half the performance. And if your plants aren’t producing ample amounts of blooms, it’s typically down to a few common growing mistakes that cause the lack of flowering.
So if you’re ready to restore that tropical paradise look to your garden, let’s uncover the reasons why your canna lilies aren’t flowering and discuss what you can do about it.
Here’s a look at what’s ahead:
How to Encourage Cannas to Bloom
Canna Care Basics
Cannas are native to tropical and subtropical regions of the Americas, and when provided with the conditions they enjoy, flowering is abundant and reliable.
A beautiful choice for beds, borders, and islands, they also make excellent potted plants. But they need large, heavy containers to anchor their abundant growth, which can become top heavy in smaller pots.
This is particularly true for species plants and older varieties that can reach heights of up to seven feet! Newer cultivars are bred to have a more compact form, growing up to three or four feet tall, making them more manageable for growing in pots and planters.
Cannas thrive in nutrient-rich, moist soil with a slightly acidic pH of 6.0 to 6.5 in a full to partial sun location.
If you’re unsure about your soil’s nutritional composition or pH, a simple meter for soil testing can tell you what amendments are needed.
You can find the Luster Leaf Mini 4-in-1 tester available from Arbico Organics.
Hardy in USDA Zones 8 to 11, they can be grown as perennials within their hardiness range. Outside of that range, they’re typically grown as annuals with the rhizomes lifted and stored for winter before planting out the following spring.
And a protected location helps them thrive – strong winds can quickly shred their large, luscious leaves.
Also, regular deadheading of spent flowers helps to encourage more blooms.
If you want to learn more about how to grow canna lilies, check out our complete growing guide for more information.
Okay, so that covers their basic cultivation needs – now let’s get on with unearthing the causes and solutions for canna lilies that aren’t flowering!
Feeding for Flowers
Plants with large ample leaves, big showy flowers, and a long flowering season tend to be heavy feeders – and canna lilies fit the bill perfectly.
Along with requiring a lot of moisture, they’re hungry for food and without a regular supply of nutrients, flowering can falter or fail entirely.
For consistent and abundant blooms, plant in fertile soil enriched with plenty of organic matter such as compost, aged manure, or worm castings, adding a generous shovelful or two to each rhizome’s planting site.
For established perennial clumps, gently work in a two-inch layer of organic matter as a top or side dressing over and around the root zone. Apply in early spring, once new growth is about six inches tall.
During the growing season, fertilize plants two or three times to meet their nutritional needs for flowering.
Slow release pellets can be applied in spring and again in midsummer, using a balanced, all-purpose NPK formula like 10-10-10.
Or a blossom booster formula with higher levels of phosphorus, such as 5-10-5 can be used instead.
Burpee’s Organic Rose and Bloom granular plant food is a good choice with a NPK ratio of 4-6-4.
Liquid or water soluble feeds with a similar NPK ratio are another option. Apply every six weeks to garden plants during the growing season, and every four weeks for container plants.
Learn more about how to fertilize canna lilies in our guide.
Full or Partial Sun?
To flower abundantly, cannas need a full sun location with eight hours of sunlight each day.
They also grow well in moderate shade, but in shady conditions they won’t produce as many flowers as they do in full sun, can become leggy, and cultivars with brightly colored foliage can appear toned down in their intensity.
In temperate regions, grow in full sunlight. However, in areas with hot and harsh afternoon sunshine, they can benefit from light shade to protect the somewhat tender foliage.
Overcrowding Issues
Overcrowding is a common problem that results in waning flower production as a result of plants having to compete for nutrients, sunlight, and water.
This problem is usually found with established perennial clumps that have outgrown their garden spot, but overcrowding can also happen with annual plantings, particularly in containers.
To restore vitality and flower production to perennial clumps, divide them every three or four years or when you notice vigor is declining.
For annual container plantings, each rhizome needs ample growing room and should have a pot at least 12 inches deep and 18 inches wide.
Multiple plants can be grown in large containers or planters, but only if each has adequate space.
Stuffing the pot with too many roots typically results in stunted growth and few, if any, flowers – these heavy feeders are not happy about sharing resources!
Proper Planting Depth
One of the most common causes of non-flowering in bulbs, including corms, rhizomes, and tubers, is planting them too deep, which can cause stunted growth or delayed blooming.
The rule of thumb for all bulbs, or rhizomes in this case, is to plant them at a depth that’s roughly twice the bulb’s height.
For canna rhizomes, that means planting at a depth of two to four inches, depending on the rootstock’s age, grade, and size, and with growing tips pointed skywards.
A hori hori garden knife with measurements on the blade is a handy tool to have at planting time.
You can find a full-tang hori hori knife with a leather sheath available via Amazon.
For potted starter plants purchased from a nursery, set out plants at the same depth as they are growing in their nursery pot.
If you’re concerned about perennial clumps being damaged by frost or freezing temperatures in winter, adding a four-inch layer of mulch to the root zone for protection is better than planting the rhizomes too deep.
Short Season Workarounds
Cannas are heat lovers and simply won’t grow in cold soil.
It’s safe to plant the rhizomes as soon as the danger of frost has passed, but they’ll sulk in the soil if temperatures aren’t toasty enough, or at least 65°F.
This means that in colder regions with short growing seasons, you won’t be planting out until late May or early June – in which case you may simply run out of time for your plants to bloom before cold weather returns.
There are a couple of ways to get around this in regions with short growing seasons.
The first is to grow dwarf varieties, because the taller the plants, the longer they take to flower.
Dwarf varieties tend to stay below four feet and will typically flower in 60 to 90 days.
But if you’re trying to grow an old style, eight-foot behemoth, these can take up to 120 days to bloom!
Growing smaller varieties like ‘Apricot Frost,’ available from Nature Hills Nursery, or this dwarf mix, available from Eden Brothers, is an easy solution to lack of flowers caused by short growing seasons.
Your second option is to start your rhizomes indoors four to six weeks before your last frost date, then transplant to garden beds or containers once the soil temperature is warm enough.
Here’s how to start your plants indoors:
- First soak your rhizomes for several hours in a bucket of lukewarm water. You can add a small dash of liquid seaweed fertilizer to boost growth if you like.
- Add two to three inches of potting soil to six- or eight-inch nursery pots.
- Set the rhizomes in place with the growing eyes pointing upwards, then cover with soil. Leave about one inch of headroom between the top of the soil and the rim of the pot for watering.
- Place the plants on a catchment saucer and water with the solution they were soaked in.
- Place in a warm, sunny spot – 70°F is the minimum temperature, with a sweet spot of 80°F for starter plants.
- Harden off before transplanting out once soil temperatures are at least 65°F.
- To harden off, place your starter pots outside in full shade for three days, light shade for the next three days, morning sun only for the following three days, then transplant out into full sun.
Choosing a dwarf type and starting the rhizomes early indoors is the best way to ensure blooming in areas with a short growing season.
Water Requirements
Consistently moist soil is another key factor in ensuring your canna lilies produce a steady supply of flowers.
When they’re stressed by drought or shallow watering, a canna’s first line of defense is to stop producing flowers!
To keep the plants producing flower stalks, water regularly, providing one to two inches of water per week.
And although there are aquatic canna lilies that love a boggy or pond environment, most garden varieties need well-draining soil to prevent issues like root rot.
To prevent the roots from sitting in wet soil or standing water, improve the soil drainage by working in some grit to the planting site using materials such as granite grit, landscape sand, pea gravel, or stone chips.
For soil with extra moisture-retentive properties, add in plenty of natural materials like coir, compost, peat moss, perlite, or vermiculite when planting, or work it in as a side dressing to established clumps in spring.
Another way to help retain soil moisture is to lay down a two- to three-inch layer of mulch over the root zone.
Apply the mulch once new growth is eight to 12 inches tall, using materials like compost, conifer needles, leaf mold, shredded leaves, or straw.
Full-On Flowers
Canna lilies are generally easy to cultivate, and ensuring their basic needs are met can quickly restore a beautiful display with full-on flowers!
Plant the rhizomes at their proper depth in a full sun location with nutrient rich soil, then be sure to fertilize at least twice during the growing season to satisfy hungry appetites.
Consistently moist soil in a well-draining environment is another key factor in ensuring a long flowering season with plenty of blooms.
Be sure to divide perennial clumps every few years to restore their vigor and promote flowering.
To work around the limits of short growing seasons, grow dwarf varieties and start them indoors for a showy floral display.
Do you folks have any favorite tips to keep your cannas flowering? Let us know in the comments section below!
And for more information about growing canna lilies, check out these guides next:
