Canna: Start Seeds Indoors or Plant Tender Bulb
How to Sow and Plant
Canna may be grown from seed sown early indoors and transplanted outside after frost, or bulbs planted directly in the garden after frost.
Sowing Seed Indoors:
- Sow indoors in March. Nicking the seed coat and soaking seed 48 hours can help improve germination.
- Plant 1 seed per 11 inch pot or large cell tray 1/4 inch deep in seed starting formula
- Keep the soil moist at 70-75 degrees F
- Seedlings emerge in 7-14 days
- As soon as seedlings emerge, provide plenty of light on a sunny windowsill or grow seedlings 3-4 inches beneath fluorescent plant lights turned on 16 hours per day, off for 8 hours at night. Raise the lights as the plants grow taller. Incandescent bulbs will not work for this process because they will get too hot. Most plants require a dark period to grow, do not leave lights on for 24 hours.
- Seedlings do not need much fertilizer, feed when they are 3-4 weeks old using a starter solution (half strength of a complete indoor houseplant food) according to manufacturer’s directions.
- Before planting in the garden, seedling plants need to be “hardened off”. Accustom young plants to outdoor conditions by moving them to a sheltered place outside for a week. Be sure to protect them from wind and hot sun at first. If frost threatens at night, cover or bring containers indoors, then take them out again in the morning. This hardening off process toughens the plant’s cell structure and reduces transplant shock and scalding.
Planting Directly in the Garden:
- Plant bulbs or seedlings outdoors after all danger of frost.
- Choose a location in full sun with rich, well-drained soil.
- Cannas may be planted in the ground or in large containers.
- Prepare the bed by turning the soil under to a depth of 8 inches. Level with a rake to remove clumps of grass and stones.
- Most plants respond well to soils amended with organic matter. Compost is a wonderful form of organic matter with a good balance of nutrients and an ideal pH level, it can be added to your planting area at any time. If compost is not available, top dress the soil after planting with 1-2 inches of organic mulch, which will begin to breakdown into compost. After the growing season, a soil test will indicate what soil amendments are needed for the following season.
- Plant bulbs 1-2 inches deep 15 inches apart. The growing points should be on top.
- Firm soil lightly with your hand, water and keep evenly moist.
How to Grow
- Keep weeds under control during the growing season. Weeds compete with plants for water, space and nutrients, so control them by either cultivating often or use a mulch to prevent their seeds from germinating.
- Mulches also help retain soil moisture and maintain even soil temperatures. For annuals an organic mulch of shredded leaves lends a natural look to the bed and will improve the soil as it breaks down in time. Always keep mulches off a plant’s stems to prevent possible rot.
- Plants need about 1 inch of rain per week during the growing season. Use a rain gauge to check to see if you need to add water. It's best to water with a drip or trickle system that delivers water at low pressure at the soil level. If you water with overhead sprinklers, water early in the day so the foliage has time to dry off before evening, to minimize disease problems. Keep the soil moist but not saturated.
- After new growth appears, a light fertilizer may be applied. Keep granular fertilizers away from the plant crown and foliage to avoid burn injury. Use low rates of a slow release fertilizer, as higher rates may encourage root rots.
- Remove spent flower heads to keep plants flowering until fall.
- Monitor for pests and diseases. Check with your local Cooperative Extension Service for pest controls recommended for your area.
- Cannas are hardy only in zones 8-10 and should be dug up and stored over the winter in colder areas. Just after the first frost dig about 12 inches from the plant to make sure you do not damage the rhizome, and lift the clump from the ground. Cannas can spread during the season and you will be likely to find considerably larger rhizomes than you planted. Wash off the roots and cut off the foliage. Allow the rhizome to dry and store between 45 and 60 degrees F.
- Cannas add a dramatic tropical look to any garden. Taller cannas make terrific herbaceous hedges, smaller varieties are ideal for containers.
- The flowers are great for cutting.
Common Disease Problems
Botrytis: This fungus causes a grey mold on flowers, leaves, stems and buds. It thrives in cool wet weather conditions. Burpee Recommends: Remove affected plant parts, avoid watering at night and getting water on the plant when watering. Make sure plants have good air circulation. Contact your Cooperative Extension Service for fungicide recommendations.
Rust: A number of fungus diseases that cause rust colored spots on foliage and stalks. Burpee Recommends: Remove infected plants. Contact your Cooperative Extension Service for recommendations.
Virus (Various causes): The most characteristic sign of virus is tight and dark green mottling of the leaves. Young leaves may be bunched. Young plants may have a yellowish tone and become stunted. Burpee Recommends: This disease is readily spread by handling. Destroy diseased plants and the plants on either side.
Common Pest and Cultural Problems
Aphids: Greenish, red, black or peach colored sucking insects can spread disease as they feed on the undersides of leaves. They leave a sticky residue on foliage that attracts ants. Burpee Recommends: Introduce or attract natural predators into your garden such as lady beetles and wasps which feed on aphids. You can also wash them off with a strong spray, or use an insecticidal soap.
Japanese Beetles: Burpee Recommends: Hand pick early in the morning into a bucket of soapy water.
Mealybugs: Mealybugs are 1/8 to ¼ inch long flat wingless insects that secrete a white powder that forms a waxy shell that protects them. They form cottony looking masses on stems, branches and leaves. They suck the juices from leaves and stems and cause weak growth. They also attract ants with the honeydew they excrete, and the honeydew can grow a black sooty mold on it as well. Burpee Recommends: Wash infected plant parts under the faucet and try to rub the bugs off. They may also be controlled by predator insects such as lacewings, ladybugs and parasitic wasps. Check with your Cooperative Extension Service for pesticide recommendations.
Slugs: These pests leave large holes in the foliage or eat leaves entirely. They leave a slime trail, feed at night and are mostly a problem in damp weather. Burpee Recommends: Hand pick, at night if possible. You can try attracting the slugs to traps either using cornmeal or beer. For a beer trap, dig a hole in the ground and place a large cup or bowl into the hole; use something that has steep sides so that the slugs can’t crawl back out when they’re finished. Fill the bowl about ¾ of the way full with beer, and let it sit overnight. In the morning, the bowl should be full of drowned slugs that can be dumped out for the birds to eat. For a cornmeal trap, put a tablespoon or two of cornmeal in a jar and put it on its side near the plants. Slugs are attracted to the scent but they cannot digest it and it will kill them. You can also try placing a barrier around your plants of diatomaceous earth or even coffee grounds. They cannot crawl over these.
Whitefly: These are small white flying insects that often rise up in a cloud when plants are disturbed or brushed against. Burpee Recommends: They are difficult to control without chemicals. Try hot pepper wax or insecticidal soap. Check with your Cooperative Extension Service for pesticide recommendations.
Why aren’t my cannas blooming? This can happen when the plants do not have enough sunlight or are receiving too much fertilizer. Cannas need full sun and should only be fertilized with a slow release fertilizer designed for flowering plants.
Can I divide my cannas? Yes, they tend to multiply quickly so feel free to divide them. When you dig them up cut back the foliage and break pieces apart that are at least 3 inches across, have several growing points and roots. Allow them to heal for a few days and store, or replant if you are in a warm zone.
Can I grow cannas in water? Cannas do like moist soils and can grow even in water if the conditions are warm. They will rot in cool wet soils. Never leave them over the winter in wet soils.
Are cannas lilies? No, cannas are often called canna lilies, but they are not related to true lilies, they are related to ginger.
Do I need to deadhead cannas? Yes they will bloom longer when deadheaded.