Will Canna Lilies Bloom Again if They Are Cut Back in August?

Flowering Period

• Planted alongside spring-flowering bulbs in March and April, most varieties of canna lily begin to bloom from May to June, sending up thick, flowering canes from amid their bananalike leaves. Their flowers, mostly in shades of orange, red and yellow, are reminiscent of those of true lilies, though cannas are not in the lily family. Individual flower stalks can persist in bloom for several weeks, and removal of flowers as they begin to fade prolongs the life of the remaining flowers on the stalk. After all the flowers on a stalk have wilted, cut the stalk to the ground if it is early in the season; if it is later in the year, in August or afterward, then cut the flower stalk just to the leaf junction -- where a leaf emerges -- to encourage the formation of a new flower stalk. Flowering continues until autumn’s first frost as long as the canna lilies are not allowed to set seed.

Proper Care and Feeding

• Cannas need to be planted properly -- 1 to 2 inches deep in soil and 18 to 24 inches apart -- in order for the plants to be vigorous and produce a multitude of flowers. Their rhizomes spread fairly quickly, and the space between the plants quickly fills up with new shoots from underground runners. Although the foliage of cannas grown in shade looks well, the plants need full-sun exposure to produce flowers. They will grow in virtually any kind of soil, and although they look best when they receive ample water, they are moderately drought-tolerant and can withstand some periods of hot, dry weather. Even though fertilizing cannas is generally unnecessary, they look fuller and flower profusely when fed with an all-purpose fertilizer every six to eight weeks throughout the growing season. Scatter 6 to 8 cups of the fertilizer per 100 square feet of growing area, and water the site thoroughly afterward.

Hardiness and Overwintering

• The abundant summer flowers of canna come at a cost, namely specialized winter care in northern climates. Some experts consider cannas to be marginally hardy in USDA zone 7 and recommend heavily mulching the plants' rhizomes in that zone to avoid freeze damage in them. After the first frost, the plants' leaves will blacken and deteriorate, after which the entire area where they grew should be mulched with a several-inch-deep layer of shredded tree bark, pine needles or leaf litter. North of, or below, USDA zone 7, canna rhizomes should be removed from the ground and stored either indoors at 45 and 60 degrees Fahrenheit or in another frost-free area in order to regrow the plants outdoors from year to year. Cannas left in the ground in such cold locations usually rot and die. Store the rhizomes in a well-ventilated area on open-rack shelves, or hang them in a repurposed mesh onion bag.

Division of Plants for More Flowers

• Although cutting back canna flower stalks in August results in new flowering canes, the time to divide canna rhizomes for replanting is shortly afterward, in September. That task may require sacrificing some flowers. Failing to divide, or thin out, the rhizomes can result in more but weaker plants. The upshot of dividing cannas is that you can propagate stronger plants in more areas of the yard. In order to divide a canna's rhizomes, simply dig up a portion of the plant’s roots, cut off the above-ground foliage and plant one or more of the old stem bases, from which the following year’s stems will grow. In USDA zone 8 and warmer zones, spring is the best time to divide canna rhizomes.