Canna lily care and overwintering

Canna lilies (*Canna* × *generalis*) are among the most structurally dramatic plants in the summer garden. Foliage ranges from bright green to bronze-purple to variegated, with flower stalks reaching 2–8 feet depending on cultivar. They are not related to true lilies (*Lilium* spp.) despite the.

Canna lilies (Canna × generalis) are among the most structurally dramatic plants in the summer garden. Foliage ranges from bright green to bronze-purple to variegated, with flower stalks reaching 2–8 feet depending on cultivar. They are not related to true lilies (Lilium spp.) despite the common name.

Cannas are tropical and subtropical plants (native to Central and South America and the Caribbean) that thrive in summer heat and humidity. In USDA zones 8–11, they are perennials that can remain in the ground year-round. In zones 4–7, they must be dug and stored over winter or treated as annuals.

Zones and hardiness

Per Missouri Botanical Garden, Canna × generalis is reliably hardy in zones 8–11 as a perennial. In zone 7 with mulching, rhizomes often survive winters with temperatures to 10°F. In zones 4–6, rhizomes must be dug after the first killing frost and stored indoors.

Per NC State Extension, in zones 7–8, applying 4–6 inches of mulch over the rhizome zone after frost kills the foliage typically provides adequate protection in most winters.

Planting rhizomes

Per Clemson HGIC, plant canna rhizomes 3–5 inches deep after the last frost date, when soil temperatures reach at least 60°F. Planting in cold soil causes poor sprouting and rhizome rot.

Spacing: 18–24 inches for smaller varieties (2–3 feet tall); 24–36 inches for large varieties (5–8 feet tall). Cannas spread by rhizome division and will fill in spacing within 2–3 seasons.

Light requirements

Per Cornell Cooperative Extension, cannas require full sun — minimum 6 hours, ideally 8+ for maximum flower production. In partial shade (3–4 hours), they grow well but flower production is reduced and stems may become slightly elongated.

Watering and feeding

Per Clemson HGIC, cannas are heavy water users during active growth. They need 1–1.5 inches of water per week and tolerate boggy conditions better than most ornamentals — some varieties are used in water gardens.

Feeding: apply a balanced fertilizer (10-10-10) at planting time, then side-dress with a high-phosphorus fertilizer (5-10-5 or similar) once per month through the bloom season. Per Missouri Botanical Garden, cannas are heavy feeders and the difference between unfed and regularly fed plants is significant in terms of flower size and frequency.

Cultivar selection

Per Penn State Extension, for container growing, choose compact varieties under 3 feet tall.

Pests: Japanese beetle and canna leaf roller

Per Rutgers NJAES, Japanese beetle (Popillia japonica) is a significant defoliator of cannas in the eastern US. Adults skeletonize leaves and chew into flowers. Hand-picking adults in the morning (when they are sluggish) is effective at small scale. Imidacloprid soil drench is effective systemically but is toxic to pollinators during bloom — avoid during flowering if possible.

Per UC IPM, canna leaf roller (Calpodes ethlius) is a caterpillar that rolls canna leaves around itself and feeds from within. It is primarily a warm-climate pest (zones 9–11 regularly; zones 7–8 in some seasons). Unroll affected leaves to expose and destroy larvae.

Overwintering rhizomes (zones 4–7)

Per Clemson HGIC:

1. After the first killing frost, cut foliage to 4–6 inches above the ground
2. Dig rhizomes carefully with a garden fork, shaking off loose soil
3. Allow to dry in a sheltered location for 24–48 hours
4. Store in barely moist peat moss, wood shavings, or vermiculite in a cool (45–50°F), frost-free location
5. Check monthly for rot; remove and discard rotted sections
6. Replant in spring after last frost when soil reaches 60°F

Per Oregon State Extension, rhizomes stored too wet rot; stored too dry, they desiccate. The medium should be slightly moist, not wet.

Common problems

Frequently asked questions

Can I leave cannas in the ground in zone 7? Per Missouri Botanical Garden, with a 4–6 inch mulch layer applied after frost, cannas often survive zone 7 winters (minimum temperatures around 0–5°F). In zone 7a (Long Island area), survival is variable depending on the specific winter. Heavy, wet clay soils pose more rot risk over winter than well-drained sandy soils.

How do I divide cannas? Per Clemson HGIC, divide rhizomes in spring at planting time, or when digging in fall for overwintering. Each division should have at least one eye (growth bud) and be at least 3–4 inches long. Cut with a clean, sharp knife. Dust cut surfaces with sulfur or allow to dry for a few hours before planting or storing.

Are cannas good for pollinators? The hybrid garden cannas produce nectar accessible to hummingbirds and some large bees. Wild canna species are better pollinator resources than most garden hybrids, which have been bred for flower size and color over nectar accessibility. Per Cornell Cooperative Extension, cannas in the landscape support hummingbird populations in summer.

Can I grow cannas in containers? Per Penn State Extension, compact varieties (under 3 feet) work well in large containers (18+ inch diameter). Use a rich, moisture-retentive potting mix and water frequently in summer — containers dry much faster than in-ground plants. Feed every 2 weeks with liquid fertilizer.

Sources

1. Missouri Botanical Garden — Canna × generalis
2. NC State Extension — Canna × generalis
3. Clemson HGIC — Cannas
4. Penn State Extension — Canna Lily
5. Cornell Cooperative Extension — Tender Perennials
6. Rutgers NJAES — Japanese Beetle Management
7. UC IPM — Canna Pests
8. Oregon State Extension — Bulb Storage