Cannas are often incorrectly referred to as bulbs, but they are technically rhizomes—underground stems that store nutrients. These tropical and subtropical plants are prized for their dramatic, banana-like foliage and vibrant, showy flowers. Proper planting technique is necessary for these heat-loving perennials to produce their best growth and most prolific blooms. Correct depth and orientation of the rhizome help ensure the plant establishes itself strongly and develops into a robust specimen.
Preparing the Soil and Location
Site selection is the first step, as these plants require full sun for optimal flowering. Full sun means at least six hours of direct sunlight daily, though afternoon shade can be beneficial in extremely hot climates to prevent leaf scorch. Cannas thrive in rich, organically fertile soil that remains consistently moist but not waterlogged.
Before planting, amend the native soil by incorporating a two to four-inch layer of organic material, such as compost or aged manure. This amendment introduces necessary nutrients and improves drainage, which helps prevent the rhizomes from rotting. Planting should be timed for late spring or early summer, after the last danger of frost has passed and the soil temperature has warmed to at least 60°F.
Proper Depth and Orientation for Canna Rhizomes
Canna rhizomes should be planted shallowly, with the ideal depth between two and four inches below the soil surface. Planting the rhizome too deep is a common mistake that can lead to poor establishment and potential rot because the underground stem is unable to dry out sufficiently.
When placing the rhizome into the prepared hole, ensure that the “eyes,” which are the small growth buds, are facing upward toward the soil surface. For smaller rhizomes, a planting depth of two inches is sufficient, while larger or more vigorous varieties can be planted closer to four inches deep to provide better anchorage. Once the rhizome is in place, cover it gently with soil and tamp the area lightly to remove air pockets.
Proper spacing ensures adequate air circulation and nutrient availability for the mature plants. Depending on the expected mature size of the variety, canna rhizomes should be spaced between one and two feet apart. Dwarf varieties can be planted closer together, while taller, more vigorous cultivars require spacing closer to two feet to allow their large foliage to develop fully without crowding.
Essential Care Immediately After Planting
Water the area deeply after planting. This deep soaking settles the soil firmly around the newly placed rhizomes, eliminating air pockets. The rhizomes are slow to sprout, and while they are establishing, the soil should remain moist but not saturated.
After the initial watering, some growers recommend withholding further watering for up to three weeks, or until the first signs of green growth appear. This temporary drying period helps prevent the dormant rhizomes from rotting before they sprout. Applying a thin layer of organic mulch, such as shredded bark or straw, helps maintain a consistent soil temperature and conserve moisture during this establishment phase. Consistent moisture becomes necessary once the shoots emerge and require regular, substantial watering.