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Canna Lily Growing Guide: How to Plant Canna Bulbs | The Old Farmer's Almanac

Cannas

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Canna Tropicanna®: The original Tropicanna, Tropicanna Gold, and Tropicanna Black

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Anthony Tesselaar Plants
Botanical Name
Canna x generalis
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Canna Lily Growing Guide: How to Plant Canna Bulbs

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Cannas are spectacular summer bulbs that thrive in the heat of July and August. Sometimes called “canna lilies,” these perennials are unrelated to true lilies. Learn when and how to plant cannas—as well as how to store cannas, which need to be dug up in colder climates.

About Cannas

Though often called “bulbs,” cannas are not true bulbs as they multiply beneath the soil from a rhizome, an underground stem. They’ll grow up to 8 feet tall in one season. Flashy and flamboyant, this perennial has distinct, paddle-shape leaves which wrap in ruffles around stems, tapering to refined buds that open into large, rainbow-hued flowers all summer-long, even in the heat of late July and early August.

They may look tropical but several species are native to the United States. The flowers are somewhat similar to an iris in shape, blooming in red, orange, yellow, and pink. Canna leaves are often heavily veined, adding even more beauty, especially when backlit by the sun. The foliage color can also vary, ranging from green to maroon to bronze, and in solid or variegated patterns. Most varieties grow between 3 to 5 feet tall, though there are taller types as well as dwarf types for containers.

“I decided that if I could paint that flower in a huge scale, you could not ignore its beauty.”
–Georgia O’Keeffe (1887–1986), speaking of her work titled Red Canna

Cannas can be both focal points and stylish accents. Use them to bring structure as a tall border or to add depth to narrow spaces. They add a colorful splash to garden orders, poolside plantings, and bring a tropical touch to water features and they thrive in boggy areas (NOT salt water). Mix cannas with grasses, lantana, zinnias, snapdragons, elephant ears, salvia, periwinkles and more. 

Note: Canna plants can be left outside in the ground all winter in zones 7 to 10. They will also grow equally well in large containers that can be dragged inside during the dormant period. In colder climates, cannas are easy to lift and store during cooler months. (Learn more below.)

Planting

Cannas need full sun for good flowering as well as consistently moist soil with a pH of around 6.0-6.5. If your garden soil is acidic (low pH), add lime before planting. Position plants out of strong wind; their large, soft leaves are vulnerable to damage.

When to Plant Cannas

  • Cannas can not tolerate cold temperatures. Soil must be 60ºF or warmer before planting rhizomes—often the time when folks put tomatoes in the ground. See our Planting Calendar for tomato-planting dates. To determine soil temps, dig a small hole 2 inches deep and insert a thermometer.
  • In cold-, short-season areas, start canna rhizomes in pots indoors or in a greenhouse to transplant outdoors at the right time.

How to Plant Cannas

  • Space rhizomes 1-1/2 to 2 feet apart to give cannas enough room. Containers need to be at least 18 inches in diameter (per rhizome). 
  • Before planting, loosen the soil to a depth of 1 foot, then mix in 2 to 4 inches of compost.
  • Dig a hole 2 inches deep and set the rhizome 1 to 2 inches below the soil with the “eyes” (bumps or nodes, which are growth sprouts) pointed up.  
  • Cover with 1 to 2 inches of soil. Tamp firmly.
  • Water thoroughly, then withhold water for as long as 3 weeks, and watch for signs of growth. Cannas are slow to sprout. Once sprouted, water at least once a week by slowly soaking the area around the roots.
  • Full foliage color develops when days are warmer (59ºF or more). Blooms should appear in 10 to 12 weeks. 
  • Cannas should not need to be staked as they have strong, upright stems.

Canna 'Tropicanna' by Anthony Tesselaar PlantsCanna ‘Tropicanna’® ‘Autumn Joy’ makes for a stunning display in late sum

Growing
  • Cannas need wet soil. If soil doesn’t remain moist, provide a good soaking once a week and every other day during the hottest weeks of summer. Water freely in dry spells.
  • Maintain a thin layer of mulch to help retain moisture.
  • Stake tall varieties, if necessary.
  • Where the soil is fertile, fertilizer is optional. However, canna are big easters and would benefit from slow-release fertilizer at planting and twice during the growing season. Fish emulsion fertilizer, a little higher in nitrogen, is a beneficial organic alternative. Higher nitrogen fertilizers tend to increase canna height. Rose or tomato food products are also suitable.
  • As flowers fade, deadhead to promote continued flowering.
  • Trimming & Pruning: Deadhead regularly to prevent plants from setting seed, which will prolong bloom.

Pruning and Cutting Back Canna

After it has been deadheaded several times and with flowers no longer forthcoming, cut the flower stem back to the foliage.

Other than deadheading, there is no need to canna unless you think the foliage looks trashy. Sometimes if it gets really hot, the leaves can get sunburnt. Trim off any dead leaves at the bottom near the stem, being careful not to nick the main stem. Pruning out dead leaves gives the plant room to grow new foliage. If the edges of the leaves are brown, you can simply trim off the brown (like a haircut). It’s as easy as that!

You may see seed pods on your canna!  These seed pods will make more cannas so you can clip off and put them right in the soil of your cannas; it may take a few years to get going but you’ve got more cannas for the future.

How to Store Cannas for Winter

In zones 7/8 and warmer, cannas cannas can be left in the ground year-round. After frost kills the foliage, cut in-ground plants back to 4 inches. Add a healthy layer of straw or leaf mulch in the fall to protect rhizomes from the cold as the plants overwinter in place. (Note: Zone 7 doesn’t always experience canna-killing winter temperatures so it’s a judgment call.) 

Bring cannas grown in pots indoors into a garage or basement for winter. Keep them dry (do not water) until spring’s nighttime temperatures are consistently above 50°F., typically after the tulips have bloomed in northern areas. Only then move them outside for the summer.

In zones 6 or colder, it is necessary to dig up (lift) in-ground cannas in the fall and bring them inside for the winter. After cutting the canna back (as above), dig out the rhizome with a shovel. Avoid damaging the rhizome by digging about 1 foot away from the stem. With your hands, gently loosen the soil and lift out the clump. Shake off the soil and cut off any foliage. Divide clumps into 3 to 5 rhizomes, each with eyes.

Cure the rhizomes in the sun or in a garage or closet for a few days to toughen them up and help them to resist rot. Wrap each rhizome in newspaper or a paper bag, along with a small about of dry growing medium, such as peat moss, to absorb moisture and prevent rot. Rhizomes should not touch each other.

Store cannas over the winter in a dry place where the temperature will not drop below 40º. Often this is a basement, attic, or garage. Check the rhizomes a couple of times over the winter to make sure that they don’t dry out. Mist with a bit of water, as needed. If you find rot, trip it away or discard the entire rhizome. 

When spring’s nighttime temperatures are consistently above 50°F., replant outdoors. Make sure each divided piece has at least one eye; from it, new leaves will grow. Blooms should appear in 10 to 12 weeks.

Harvesting

Cut canna flower stems for indoor arrangement. The flowers carry their tropical appeal in the vase. The flowers die in a day or two. However, the foliage continues to make a beautiful backdrop to many bouquets.

Wit and Wisdom
  • Cannas’ bright flowers may attract hummingbirds.
  • The name canna comes from the Greek word kanna, meaning “reed” or reedlike plant.
  • During the Victorian era, gardeners so loved cannas that they grew them from seed, but this isn’t easy. The germination rate is low, and the seeds need to be filed or given an acid bath to break down their hard coat. 
Pests/Diseases
  • Canna are seldom bothered by deer nor prone to disease. Rust, fungal leaf spot, Botrytis blight, and bacterial bud rot may happen when cannas are kept too wet and crowded.
  • Cannas rarely have issues with pests, though caterpillars can munch on leaves. Slugs, snails, spider mites, and caterpillars are most common culprits.

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