Cannas are tropical plants grown for their dramatic, paddle-shaped foliage and vivid flowers, bringing an exotic presence to the garden. While often called canna lilies, they belong to their own family, Cannaceae, related to ginger and bananas. Canna flowers are produced sequentially and can last continuously from mid-summer until the first hard frost in temperate climates. This extended period of color depends on the plant’s growth cycle and the gardener’s maintenance practices.
The Standard Canna Blooming Season
The flowering period of a canna is a continuous process powered by the underground rhizome structure. In optimal conditions, cannas can bloom for approximately three to four months, typically starting in June or July and continuing through October. The total duration is directly tied to the local climate, specifically the date of the first frost and the time the rhizome was planted in spring.
Canna flowers emerge on tall, upright stalks featuring multiple buds, forming a spike. An individual flower only lasts for a few days before fading, but the spike produces new flowers in succession over several weeks. Once the flowers on the primary spike are spent, the plant produces new flowering stalks from the rhizome, ensuring a constant rotation of blooms throughout the season.
The length of the bloom season is also influenced by when the rhizomes are planted. Those started indoors four to six weeks before the last expected frost date typically bloom earlier. In regions with long, hot summers, this sequential flowering allows the plant to provide color for the entire growing season. The plant continues producing new shoots and flowers until environmental signals, such as consistently cool temperatures or freezing conditions, force it into dormancy.
Cultural Practices for Sustained Flowering
To maximize and extend the blooming period, specific cultural practices must be applied consistently throughout the growing season. The most direct intervention is deadheading, which involves removing spent blooms and flower stalks. Deadheading is effective because it prevents the plant from diverting energy into seed production, which is the plant’s natural signal to stop flowering.
The specific technique for removing spent flowers depends on the stage of the flower spike. As individual flowers fade, they can be pinched or snipped off to tidy the plant without removing the entire spike, as new buds are often located directly next to the spent ones. Once an entire flower spike has finished producing blooms and no new buds are visible, the stalk should be cut back to the next emerging side shoot or to the base of the plant. This encourages the canna to focus its resources on developing a new flowering stalk from the rhizome, extending the overall bloom time.
Consistent nutrient management supports continuous flowering, as cannas are considered heavy feeders. Fertilizers used during the peak growing months should provide a balance of nutrients, focusing on phosphorus, which supports vibrant bloom production. A fertilizer blend such as 5-10-5 or 10-10-10, applied monthly or every four to six weeks, provides the necessary elements for healthy foliage and abundant flowers. Avoid over-application of nitrogen-heavy fertilizers, as this nutrient primarily encourages lush leaf growth at the expense of flower development.
The plant’s tropical nature dictates a consistent need for moisture, and irregular watering can create stress that shortens the flowering season. The soil must be kept evenly moist throughout the summer, particularly during the bloom period. Deep watering once or twice a week is generally recommended. Hotter climates or container-grown plants may require more frequent attention to prevent the soil from drying out completely.
Managing the Plant After Flowering Ends
The summer bloom cycle naturally concludes when seasonal environmental factors signal the end of the growing period. The most definitive end to the flowering season is the arrival of a hard frost, which causes the foliage to turn black and signals the plant to enter its dormant state. The plant ceases flower production and begins to store energy in its underground rhizomes for the following year.
In warmer climates (USDA hardiness zones 8 through 11), the rhizomes can survive the winter in the ground. After the foliage is killed by frost, the stalks should be cut back to about six inches above the soil line. A thick layer of organic mulch can be applied over the cut stalks to provide insulation and protection for the rhizomes left in place.
For gardeners in colder regions where ground temperatures regularly drop below freezing, the rhizomes must be lifted and stored to survive the winter. This process is performed after the first light frost causes the foliage to yellow but before a deep freeze sets in. Once the foliage is cut back, the rhizome clumps are dug up, cleaned of excess soil, and allowed to dry for a few days in a cool, shaded area.
The cleaned rhizomes are stored in a cool, dark, and dry location, such as a basement or unheated garage, where the temperature remains above 40 degrees Fahrenheit. Storing them in a medium like dry peat moss or vermiculite helps regulate moisture and prevents them from drying out during dormancy. This winterizing procedure ensures the rhizomes remain viable, ready to be replanted in the spring for another season of sequential blooms.