What Are Cannas.
There is nothing in the plant kingdom remotely like Cannas. Classified in their own plant family Cannaceae, in which there is only one genus Canna, it can be said that few other plants are as remotely connected to the remainder of the plant world. The closest living relations to Cannas are the other plant families of the order Zingiberales, which are the Gingers, Bananas, Marantas, Heliconias, Stelitzias, etc. In general, these are all tropical herbaceous plants having large leaves which open by unfurling.
Although Cannas are now naturalized in many tropical countries of the world, they originated in the Mid-Americas from Florida through the Panama to the warmer parts of South America and the West Indies. For over 4000 years the plant was cultivated by the native American people, who ate the rhizomes, and used the large leaves for various purposes. Today Cannas are cultivated all over the world, there are over 350 named species and cultivars.
Cannas are very easy to grow. A rhizome started into growth in Winter/Spring in a cool greenhouse, and planted out when frosts are over will start to flower in mid-summer, and will continue to flower through summer and autumn, each stem producing a succession of flower spikes, with more stems coming from the base. They will continue to grow until cut down by the winter frosts. At the end of the growing season the initial rhizome will have multiplied, and each new rhizome will produce a flowering plant the next year. They have no serious pests in temperate climates. They grow best in full sun or dappled shade with some shelter, in a rich soil or compost. Cannas may be grown as outdoor bedding or centerpiece plants where they will happily co-exist with other vigorous plants and lend an exotic tropical touch to wherever they are grown. They may also be grown in outdoor pots and containers, but the smaller varieties are particularly suited to pot and patio cultivation, where they will begin to flower early while still quite short. They may also be grown as indoor conservatory plants, being protected from the weather they will make a spectacular display, producing leaves and flowers of exquisite perfection. However, being vigorous plants, they require plenty of overhead light.
Growing From Rhizomes.
The earlier a rhizome is started into growth, the sooner it will flower. In Europe and other cool northern hemisphere countries, rhizomes will start to grow of their own accord in a cool greenhouse in March, no heat being required except to protect against frost, and they will then be ready to plant out when the danger of frost is over in late May or early June. Some gardeners over winter Cannas in the ground or plant rhizomes directly in the ground, this is fine in warmer climates, but in areas prone to frost they need protection under mulch. However, in colder climates, Cannas over wintered in the ground will be later flowering and some may not flower at all. Plants for indoor display can be started into growth at anytime, and will continue to grow and flower as long as they get adequate food, warmth and light.
If you have purchased a rhizome, if at all possible inspect it yourself to make sure that it has growing points that will become shoots. Take great care when unpacking- any new shoots at this stage are extremely fragile, and a shoot broken off represents a whole years worth of lost flowers. New rhizomes should be immediately potted up, irrespective of the time of year; they just feel more comfortable surrounded by damp compost. If immediate potting is impractical, the rhizome should be covered in damp peat. Canna rhizomes do not normally enter a totally dormant stage, and if they are thoroughly dried out, then some will be lost.
Individual rhizomes may be planted in 1-2 litre pots, using rich compost. Alternatively, 3 or more rhizomes maybe planted in a 3 litre pot and this will make a more busy plant with more flowering spikes. Rhizomes need to be planted just below the surface of the compost. There is no right or wrong way up, the rhizome will sort that out for itself. Water the compost and put the pots in a light place, protect from frost, and if you can provide a little heat then so much the better, but this is not essential. Take great care with the emerging shoots, which are fragile. Slugs, snails and aphids seem to have a liking for newly emerging shoots, so watch for these problems and treat as necessary.
The ideal site for Cannas is a warm protected spot where they will get plenty of light. They do not like open and exposed sites where they will become windswept and tattered. They will grow in damp places, even waterlogged places, and can also withstand dry conditions. They grow well in sandy soil, on chalk, and also in heavy clay. They will grow in full sun, indeed they love it, but the sun’s rays may bleach out some of the co lour from the flowers and leaves. They are not happy under trees, particularly if surrounded by other tall growing plants, and under such conditions they may not thrive. The best site is one of dappled sunlight.
Preparing The Soil.
Prepare the planting ground as if you were growing hungry plants such as tomatoes or potatoes, because Cannas are equally vigorous. The soil needs to be dug, the deeper the better, and compost/manure/fertilizer added. The more you dig, water, and feed, the better they will grow. If you simply scrape a hole in hard soil and expect a Canna to thrive, then forget it!
Caring For Cannas.
During the growing season, Cannas require a little attention. They are strong and sturdy plants, even the tall varieties require no staking, it is very rare to see a Canna which has blown over, whatever its location. They are amazingly tolerant and gutsy plants, and as with many other gutsy creatures, they have a good appetite for both food and drink, so keep them well watered, and provide a little feed now and then. If they are starved of nourishment, they will become pale and spindly, but will still flower.
Rhizomes should be lifted in the autumn, typically early October, or after the first hard frost has killed the foliage. A single rhizome planted in the spring will have multiplied by the year-end to give around 4 to 8 rhizomes which can be saved for the following year, when they will grow and flower, completing the cycle. Dig them with a fork, taking care not to damage or separate the clump of rhizomes. Place the whole clump, still undivided, and with the soil still around it, in an empty plastic container such as a large flower pot. If you separate the rhizomes from the clump at this stage, you will loose more than if you left it entire. Cardboard boxes are too dry, Cannas like to be damp, even when dormant. Store the clump in a frost free place, such as in a garden shed, garage, or under the greenhouse bench. The ideal temperature is around 8-10 c. If the clump is looking very dry, then sprinkle it with water