Often grown for their dramatic foliage - large banana like leaves - Cannas are vibrant tender perennials that provide a strong ornamental interest and immediately give a touch of the tropics in the garden or containers. Impossibly exotic, they bloom prolifically from mid summer to the first frost in a flamboyant array of colors varying from red, orange, yellow, pink or cream. Their architectural shapes and eye-catching colors make them perfect for planting as focal plants or massed to create a tropical effect. Easy to grow, they stand proud and bold provided some basic rules are respected.
1. Choose The Right Rhizomes (or Tubers)
- Choose rhizomes that are large, firm, and plump.
- The number of eyes (growth points) of the rhizomes is highly correlated to the overall size of the plant and its blossoms. The more eyes, the bigger the plant and more spectacular the flowers.
- The optimum number of eyes should be 3-5.
2. Select The Right Site
- Best flowering occurs in full sun in organically rich, moist and well-drained soils. Canna lilies will survive in the shade but best flower production is obtained in full sun - except in hotter climates where part shade will enable the flowers to last longer.
- Choose a sheltered spot and soil that has been improved by digging in well-rotted manure or garden compost.
3. Planting Your Canna Lilies
- Canna rhizomes can be planted from spring (after all danger of frost has passed) through early summer. They may be started indoors as early as a month before the average last frost date (for earlier blooms) or planted directly in the ground after the danger of frost has passed.
- As they come from tropical and subtropical regions, cannas are heat-loving plants. If conditions are cool or soil temperature is cold, delay the planting until the soil has warmed to at least 65°F (18°C).
- Plant your canna rhizomes 4 in. deep (10 cm).
- Planting distance varies with the size of your canna plants. Dwarf cannas (less than 18 in. tall) should be spaced 18 in. apart (45 cm), medium and standard cultivars about 2 ft. (60 cm), and tall vigorous canna varieties (over 5ft. tall) about 3ft. (90 cm).
- Set the canna rhizome with the growing tips facing up. Cover the rhizome with soil and water as needed. Mulch to keep down weeds and conserve soil moisture.
- Provide consistent moisture during the growing season and do not allow the soil to dry out. After flowering, you may reduce watering.
- Cannas are greedy feeders. Apply a general purpose fertilizer in mid-season to promote a brilliant display.
- Deadhead Cannas throughout the growing season to keep them blooming for as long as possible. When a flowering spike has no more buds, it can be removed with shears or a sharp knife down to the next side shoot, where another flowering spike will emerge. Usually, canna produce 2-4 spikes per stem. When the stem is entirely spent, it can be removed from the base (usually at the end of the season).
- Most canna lilies are winter hardy in zones 8-11, so in these warm climates the rhizomes can be left right in the ground. If you live in a colder area and you want to save your rhizomes for next spring, you may dig them up before the first frost and store them over winter before replanting them next spring. Not sure about your growing zone? Check here.
- As soon as temperatures drop below freezing and the foliage turns brown, cut down the foliage and stems to about 6 in. (15cm), and lift the rhizomes for winter storage. If you are growing different varieties of canna lilies, you should label them.
- Remove surplus soil, dry and then store in trays in barely-damp wood vermiculite or multi-purpose compost. Place in a frost-free position for the winter, no higher than 50°F (10°C). Little, if any, watering should be necessary.
- Check the rhizomes during the winter months to make sure they are not too moist or too dry.
6. Water Cannas
- Water Cannas are generally hybrids of Canna glauca. They can be grown in wet soils, along with other bog plants, and can be planted in baskets, with up to 6 in. (15 cm) water above their rootstock.
- The basket, at least 12 in. across (30 cm), should be filled with loam-based compost. Slow-release fertilizers like those intended for water lilies can be added.
- Plant your canna at the normal height and cover the surface of the basket with gravel or chunky cobbles. After planting, keep the basket in shallow water to enable your water canna to get acclimatized.
- As a precaution in winter, take the basket under cover into a frost-free greenhouse or conservatory. Keep the pots moist but not saturated. In late spring, plant the sprouted plants out when the risk of frost has passed.