When to Plant Cannas: After-Frost Timing, Depth and Winter Storage

Cannas (Canna × generalis and relatives) are tropical and subtropical plants grown from thick rhizomes (UMN). They aren't true lilies, even though they are often sold as "canna lilies." NC State says they can reach 8 feet tall, and UF/IFAS notes cultivars range from a few feet to over 15 feet. Their big paddle leaves come in green, bronze, purple and striped forms, so they look good even before the red, pink, orange or yellow flowers open (UMN). Red-flowered kinds draw hummingbirds (NC State), and UMN notes bumble bees visit some varieties.

When to plant cannas by region

Our planting calendar shows your average last spring frost. Count back 4 to 6 weeks for an indoor start, and plant outside once nights stay warm, around the time you set out tomatoes and peppers (GardenPal suggestion).

How deep and far apart to plant cannas

Watering, feeding and deadheading

• Water about once a week in dry weather (Iowa State). UMN says cannas grow best with adequate moisture.
• Feed: Iowa State works a balanced fertilizer such as 10-10-10 into the bed before planting and adds it once or twice more during the season. UF/IFAS feeds monthly with a balanced fertilizer or less often with a controlled-release one.
• Deadhead spent flowers to keep plants tidy and encourage more blooms (Iowa State). UF/IFAS notes some cultivars drop their old flowers on their own.
• Bloom time: July to October in North Carolina (NC State), early summer through fall in South Carolina (Clemson).

Cannas in containers

Dwarf cultivars add height to mixed pots of annuals (Clemson), and UMN calls cannas excellent plants for large containers. Use a big pot with drainage holes and keep it watered, since a large canna in a small pot dries out fast (GardenPal note). Clemson also mentions seed-grown cultivars that flower about 90 days from sowing.

Digging, storing and dividing

• When to dig: after frost blackens the leaves (UMN). NC State says cannas are injured if left in the ground below 25°F and, in zone 6, cuts them down right after the first frost.
• How: cut the stems back to 2 to 3 inches, let the rhizomes dry, and store them in a box (UMN) or in dry peat or vermiculite (NC State).
• Storage temperature: cool but frost-free, 40 to 50°F, such as a basement (UMN); NC State gives 41 to 50°F.
• Mild areas: cannas can stay in the ground in zones 7 to 10 (Clemson); NC State mulches them in zone 8. In Florida, UF/IFAS cuts cold-damaged plants to 6 to 8 inches and they regrow.
• Divide every few years; each piece needs an eye, or growing point (UMN). UF/IFAS divides crowded clumps after the bloom season and replants quickly.

Leaf rollers, beetles and pet safety

In the South, the main pest is the canna leafroller. UF/IFAS says the larger canna leafroller is the caterpillar of the Brazilian skipper butterfly. It cuts a leaf flap and ties it over itself with silk, and several large caterpillars can strip a plant. It is well established in Florida, Texas and southern Arizona. Look for rolled leaf edges, especially on red-leaved cannas and red or orange flowers (UF/IFAS Florida-Friendly Landscaping). Hand-picking is the simplest fix (UF/IFAS Florida-Friendly Landscaping). Sprays are hard to target inside the rolls; UF/IFAS says Bt (Bacillus thuringiensis) products are the best choice if needed, used on small caterpillars and following the label. NC State also lists Japanese beetles, slugs, snails, rust, bud rot and viruses, though Iowa State says none of the canna problems are serious. For pets, the ASPCA lists garden canna as non-toxic to dogs, cats and horses.

Cannas around the vegetable garden

Tall cannas make a summer screen or backdrop on the north side of the vegetable garden, where they won't shade shorter crops (GardenPal suggestion). They like the same heat and steady water as squash and peppers, and NC State notes they suit rain gardens and pond edges. For other summer bulbs planted after frost, see when to plant dahlias, when to plant gladiolus and when to plant calla lilies.

Frequently asked questions

When should I plant canna bulbs?

Outdoors after your last spring frost, once the soil has warmed (UMN, NC State). You can start them in pots 4 to 6 weeks before the last frost for earlier flowers (Iowa State).

How deep do you plant canna rhizomes?

4 to 5 inches deep (Iowa State); NC State uses 4 to 6 inches. Indoors in pots, 3 to 4 inches (UMN).

How far apart should cannas be planted?

12 inches to 3 feet apart (NC State), depending on how big the variety grows.

Do cannas come back every year?

In zones 7 to 10 they usually do (Clemson). In colder areas, dig the rhizomes after frost and store them at 40 to 50°F (UMN).

Do cannas need full sun?

Full sun gives the most flowers. They grow in part shade but bloom less (Clemson).

Are cannas poisonous to dogs and cats?

The ASPCA lists garden canna as non-toxic to dogs, cats and horses.