Flowers

How to Grow Canna: Planting, Spacing, Care & Dig-Store

Quick answer

Start rhizomes indoors 4 to 6 weeks before average last frost (Iowa State). Plant outdoors after last spring frost (NC State). UF allows rhizomes about 2 weeks before last frost in warm regions. Dig after frost in cold zones and store cool — method on the dig-store page.

Canna at a glance

PlantStart indoors: 6–4 wk before last frost; Transplant: last frost
SunFull sun (6+ hours) to partial shade; high organic matter; moist, well-drained soil.
WaterWater about once a week in dry weather (ISU).
SpacingISU: indoor cover 3–4 inches; outdoor plant 4–5 inches deep.
Days to harvestFoliage/flower ornamental; season to frost (NC)
-7-6-5-4-3-2-1LF+1+2+3
■ Start indoors   ■ Plant out   ■ Harvest
Weeks relative to last frost (LF). Colored weeks show when our ZIP planner schedules each step.
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Updated

Canna (Canna × generalis / Canna spp.) — tender rhizome. Dig-store how-to lives on the peer dig-store page; this page covers planting and care.

Canna flower
Canna flower (Canna indica group). Photo: Dolon Prova, Wikimedia Commons, CC BY-SA 4.0 (resized).

Sourced from university extension guides. For dates where you live, use the ZIP planting planner.

Planting timing

Iowa State: “Start canna rhizomes indoors 4 to 6 weeks before the average last frost date in your area. Plant the cannas in large pots. The rhizomes should be covered with 3 to 4 inches of potting soil.” Outdoor depth about 4 to 5 inches. (ISU canna start; ISU tender perennials) NC State: plant rhizomes after the last spring frost, at least 5 inches deep and 12 inches apart. (NC State Canna × generalis) Footnote: UF says rhizomes may go in about two weeks before the last spring frost in Florida-facing conditions; potted plants anytime in warm months. (UF/IFAS cannas) Planner: Start indoors last frost −6 to −4; Transplant / plant outdoors last frost 0 (prefer NC after-frost rule for cold-climate planners).

Depth and spacing

ISU: indoor cover 3–4 inches; outdoor plant 4–5 inches deep. NC: outdoor ≥5 inches deep, 12 inches apart; height about 2–6 ft; width about 1–2 ft.

Sun, soil and water

Full sun (6+ hours) to partial shade; high organic matter; moist, well-drained soil. Flowers poorly in deep shade (NC State). Water about once a week in dry weather (ISU).

Care and dig-store

Deadhead spent flowers (NC/ISU). In cold zones, dig after the first frost and store in peat or vermiculite at about 45–50°F (NC). Warmer zones may leave rhizomes in soil with mulch after cutting frost-killed foliage. For storage method peers see dig and store dahlias and cannas.

Pests and diseases

NC State: Japanese beetles on young leaves and buds; aster yellows; slugs/snails; bud rot. Japanese beetles (UMN): handpick or knock into soapy water morning/evening; neem oil (repeat; less effective at high numbers; low bee risk when used as labeled); Bacillus thuringiensis galleriae products moderately effective about 1–2 weeks and not toxic to bees. (UMN Japanese beetles) Slugs: handpick or iron phosphate bait as labeled (UC IPM snails and slugs). Remove plants with aster yellows; keep drainage for bud rot.

Related: dig-store dahlias & cannas · caladium · elephant ear · ZIP planner · organic pest control

Frequently asked questions

When do I start cannas indoors?

4–6 weeks before average last frost (Iowa State).

When do I plant cannas outside?

After last spring frost (NC State). UF allows rhizomes about 2 weeks before last frost in warm regions.

Do I dig cannas for winter?

In cold zones yes — dig after frost and store cool/dry (NC State). Method details: dig-store peer page.

Sources