Did you placed your canna lily somewhere in full sun?
Do you keep the soil consistently moist?
Did you provide your canna with a regular supply of nutrients?
Are you dividing your canna lilies every 2-3 years?
Did you prune your canna at the end of the growing season?
Canna will not flower if it is not getting adequate sunlight. Canna lilies need at least 6 hours of sunlight each day. If your cannas are potted, move the pots to a sunnier place, and if they are planted in the shady part of the garden, all you can do is to replant them.
Canna lilies require consistently moist soil. The soil must be well-draining to prevent rots, but it should still retain moisture. When stressed by drought or inadequate watering, canna lilies will reserve their moisture by sacrificing blooms.
If not supplied with enough nutrients throughout the growing season cannas will not be able to bloom. For best blooms fertilize your cannas 2-3 times throughout the growing season with a general 10-10-10 fertilizer.
Overcrowding is one of the most common reasons for cannas not blooming. Canna plants that have to compete for water, nutrients, or sunlight will not bloom. Divide your cannas every 2-3 years, and you shouldn't have problems.
Your canna lilies may have been planted too deep. Canna lily rhizomes should be planted no deeper than 2-3 inches. Planting canna lily rhizomes too deep can cause the plants to be stunted or have delayed bloom time.
Canna lilies require annual pruning to grow each year. After the first frosts appear in the fall and kill off the current season's growth, prune canna back so that it is roughly 6 inches tall. Pruned cannas will produce blooms, while cannas that are not pruned may be unable to do so.
https://www.hunker.com/13426231/why-are-my-cannas-not-blooming
https://www.gardeningknowhow.com/ornamental/bulbs/canna/canna-lily-will-not-bloom.htm
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Sreten null
Hi! I’m Sreten Filipović. I graduated from the Faculty of Agriculture at the University of Belgrade, with a master's degree in Environmental Protection in Agricultural Systems. I’ve worked as a researcher at Finland's Natural Resources Institute (LUKE) on a project aimed at adapting south-western Finland to drought episodes. I founded a consulting agency in the field of environment and agriculture to help farmers who want to implement the principles of sustainability on their farms. I’m also a founding member of the nonprofit organization Ecogenesis from Belgrade whose main goal is non-formal education on the environment and ecology. In my spare time, I like to write blog posts about sustainability, the environment, animal farming, horticulture, and plant protection. I’ve also published several science-fiction short stories.
You can find me on LinkedIn at https://www.linkedin.com/in/sreten-filipovi%C4%87-515aa5158/