Description

Cannas are typically grown for their continuous summer flowers and vertical wide-leaf foliage. The plants are large tropical and subtropical herbaceous perennials with a rhizomatous rootstock native to areas with a summer monsoon and dry winter. They can be grown as flowering summer patio plants. If growing as a potted plant and trying to overwinter, allowing the foliage to frost is ok, it will not kill the root system. However, do not allow the pot with rootball to freeze solid or go below 20 degrees for more than a few hours; move into a cold garage or basement over the winter with no watering. Cut back and allow to go dormant and place entire pot back out in April or May with a time-release fertilizer. Another more labor intensive way to overwinter cannas is to remove them from the dirt, dust with fungicide, place in box with sawdust, and keep in the refrigerator. We consider this method old-fashioned and too much work but ok if you only want to save a few pieces. If digging from the ground, just save a chunk with the dirt intact and place into a large pot in the garage. During the growing season, fertilize, water regularly, and place in full sun. You may also plant these in the ground for an enormous tropical effect! It is possible to overwinter these in the ground in Kansas by mulching 4-8" thick over deeply planted rhizomes. New growth will usually be slightly delayed but quick to regain full height. In our trial gardens in Lawrence, KS (zone 6a), the following varieties survived after being mulched 6-12" with leaf mulch to -17 degrees F. (Canna 'Daddy's Buckaroo',Canna 'Omega',Canna indica 'Red Stripe',Canna indica 'Ellen's Super Orange', Canna indica 'Wyoming') During the arctic blast of February, 2021, lows down to -17 degrees F on Feb 16th, 2021 were recorded. The longevity of this cold blast was also impressive: 10 days on a row with highs of 10-15 degrees F or lower, 8 nights of lows in the single digits and negatives, and 36 straight hours of 0 degrees F and mostly lower. Canna 'Omega' is a tall variety with blue-green leaves and orange flowers. This variety is the most cold hardy of the cannas due to its vigorous deep growing rhizomes. The rate of spread is faster so provide a larger space for this plant. This canna can also grow in standing water as a potted plant in water gardens or rain gardens.