Here at Gardening Know How we get lots of questions, and our goal is to provide answers to those inquiries to the best of our knowledge. The stunning canna lily is fairly low maintenance but even so can have a gardener scratching his or her head. The following information includes the 10 most commonly asked questions about canna lilies.
Cannas need it to be quite warm or they won’t bloom. Also, it takes quite a bit of energy to produce such an impressive blossom. My cannas took so long to bloom last year I had almost despaired. I had gorgeous foliage for months but not a hint of blossom. There were probably a couple of reasons for this. My cannas were in pots so may have needed more water or fertilizer than I provided. Cannas should be fed a fertilizer each month that is higher in phosphate, and they should be kept quite moist.
Although canna plants like the heat, there is such a thing as too much of a good thing. If you live in a very warm region and they are in full sun, they may be getting sunscald. Try shading them or, if they are potted, move them out of the hot afternoon sun. Another reason for brown leaves may be a lack of irrigation but that would likely be accompanied by general wilting. Also, if your cannas are potted, they may have become root bound and unable to uptake enough nutrients and water which may make the edges of the leaves brown. Lastly, the leaves may be turning brown signaling the natural end of the growing season.
Absolutely! That said, however, be sure to provide them with a large enough container to sustain root growth. If the pot is too small, the plant won’t be able to take in enough nutrients or water and it will falter. Also, the larger the pot, the more bulbs can be planted which will make the container “pop” with color and texture. Be sure that container grown cannas have drainage holes in the bottom. Add a layer of pebbles or small rocks to the bottom of the pot to facilitate drainage as well. Fill the pots almost to the top and plant the canna tubers 4-5 inches (10-13 cm.) deep. Water them in well and continue to provide consistent irrigation. Fertilize each month with a food that is high in phosphate.
Cannas need a lot of food to produce those truly impressive blooms. They need a plant food that is high in phosphorus to encourage blooming. To give them a jump start, at planting, incorporate compost into the top 8 inches (20 cm.) of soil. Prior to setting the canna bulb, sprinkle 1/3 cup (40 g.) of a 12-4-8 fertilizer into the planting hole. Thereafter, fertilize each month with 2 lbs. of a 5-1-5 fertilizer per 100 square feet of garden. Work the fertilizer into the soil between the plants but avoid getting it on the leaves. In late summer, cease fertilizing, which will encourage tender new growth that can be damaged by upcoming cold temps.
Absolutely, and it’s fun and fascinating. Although many of the plants with stunning blooms are hybrids which won’t stay true to seed, pretty much anything you get from propagating canna lily seeds will be amazing. Once the canna is done blooming, it will produce a green pod that contains 1-3 seeds. When the pod is dry, the seeds will pop right out. Because the outer seed is so tough, it needs to be soaked in lukewarm water for a minimum of 24 hours or scarified with a nail file to scrape off the seed coat prior to planting. It can then be planted in your medium, watered, and covered in plastic wrap. Keep the seed at a constant temp of 70-75 F. (21-24 C.). Germination takes 1-2 weeks at best or even up to a month.
There are two camps as to whether to deadhead a canna lily. The point of deadheading is to remove the spent flower before it goes to seed. Going to seed takes up precious energy that could instead be used to produce additional blossoms. Some cannas produce big seed pods and others are sterile. If you know your plant is sterile, then there is no reason to remove spent blossoms. If the plant produces seed however, carefully pinch off the spent canna blooms. I say carefully because new buds form right up against the spent flowers and you’re liable to snip them off too. Not that that will hurt things, it will just take longer for the plant to flower again.
There are a number of factors that can result in a plant with yellowing leaves. The plant may be getting too much water or too little. It could just a signal of the end of the seasons growing cycle when yellowing leaves and drop off are a natural sign the growing season is coming to an end. If your cannas are in pots, they may have a nutrient deficiency or excess salt in the soil. The pH may be too high, resulting in leaf chlorosis; use a pH meter to check. Lastly, a fungal disease called canna rust might be the culprit. This fungus causes orange, yellow and brown spots on the leaves and stems. If the infection is severe, the entire leaf will turn brown and yellow. Remove and destroy any infected leaves and severely infected plants.
Probably, yes. With gorgeous sword-like large leaves, it isn’t any wonder that canna lily pests like to sink their teeth into them. If the holes are at the base of the plant, it could be slugs or snails nibbling away. Otherwise, the most likely culprits would be caterpillars and their larvae. The larvae of Brazilian skippers, leaf rollers, can chew rows of holes through canna leaves, as can the corn earworm and woolly bear caterpillar. Not to worry, a few holes in the plant will not damage it. Luckily, these pests are large enough to see and remove by handpicking. Just pluck them from the leaves and drop them into a bucket of soapy water.
Wait until the first frost has killed the foliage and then lift the bulbs from the ground. It is likely that the bulbs multiplied over the summer so don’t be surprised if you are digging out more than you planted. Separate the canna bulbs and cut the foliage back to 2-3 inches (5-7.6 cm.). Gently rinse, don’t scrub, the dirt from the bulbs. Allow the canna bulbs to dry or cure by placing them in a dry area for a few days. Store the canna bulbs wrapped in newspaper or paper bags in a cool, dry place such as a garage, basement or closet.
Yes, you can divide and transplant canna lilies. In fact, the cannas will bloom more prolifically and healthily if they are divided every 3-5 years. Plan to divide the canna at the end of the summer to early fall when the plants are done blooming and the foliage begins to die back. Carefully dig up the plants and look for the joints where new rhizomes grow from older ones. Then either break them apart or cut them with a sharp knife. Make sure that each section has at least one eye and some roots. If you live in a warmer region, go ahead and replant the divided canna 6 inches (15 cm.) deep. If you live in cooler areas, USDA zone 7 or less, allow the rhizomes to cure or dry for a few days and then store them over the winter in newsprint or paper bags in a cool, dry area. Then when all danger of frost has passed for your region, plant the rhizomes in the garden or pot.
We all have questions now and then, whether long-time gardeners or those just starting out. So if you have a gardening question, get a gardening answer. We’re always here to help.