What are Cannas?

WHAT ARE CANNAS?

Canna are exotic tropical-looking plants which are often seen in municipal and public gardens where they form spectacular bedding displays and centerpieces.

HISTORY

The wild cannas originated in the tropical and sub-tropical Americas. The indigenous Americans used them for food. They continue to be used for food in parts of Bolivia and Colombia.

With the European colonisation of central and southern America, plants were brought back to Europe. There is records of them being grown in the gardens of England and France in the 16th Century. A notable horticultural advancement in cannas is due to the Frenchman Theodore Annee who was a diplomat stationed in Chile in the 19th Century. He introduced several named varieties into European horticulture. Cannas at that time were grown primarily for foliage and had small flowers. The French horticulturalist Crozy succeeeded in breeding large hybrid cannas in the 1870's. Many more large flowered varieties were developed by breeders in France, Italy, Germany, Hungary and the USA. These were exported around the world. Cannas are now naturalised in many countries, and in some countries are invasive.

BOTANY AND TAXONOMY

Botanically, cannas are members of the family Cannaceae, in which there is only one genus, Canna. This means that they are very different to anything else in the plant kingdom. There is no other plant in nature which is like a canna. But because there is only 1 genus, they are all very much like each other.

Within the Canna genus, there are presently thought to be either 9 or 23 species (ie truly wild cannas). It may seem odd that botanists haven't been more specific about the number of species, and the reason is that there are 2 expert taxonomists who have studied cannas in the wild, the japanese botanist Nobuyuki Tanaka, and the Dutch botanist Hilga Maas. Tanaka came to the conclusion that there were 19 species, and Maas decided that there were only 10 species. The difference is mainly that C. indica is a very variable species, and where C. indica ends and another species begins is arguable. Since these erudite papers were written, 4 more species have been discovered. The closest relations to cannas are the gingers (Zingiberaceae), bananas (Musaceae), strelitzieas (Strelitzeaceae), heliconias (Heliconiaceae), and marantas (Maranteaceae).

To read more abot the taxonomy of cannas, see
Taxonomy

GARDEN CULTIVARS

There are many types of canna. Some are giants growing 2 meters tall or more (up to 8 ft). Some are very short and remain about 0.5m (18 inches). Some are mainly grown mainly for the foliage and have small flowers, and some for large flowers. The foliage can be in shades of green and bronze, or striped. Flowers are generally shades of orange, red, yellow, pink, cream.

The basic types of cannas can be grouped as follows:

• Floral cultivars These are the cannas that are most commonly found in parks, gardens and municipal plantings. They have beautiful flowers and gorgeous foliage. Typically they are around 1.5 meters tall, but some floral types are large plants, up to 2 meters tall while some are quite short, around 0.5 meters. These cannas are propagated by division or rhizomes. There are virtually none that can be grown from seed, firstly because most garden hybrids are sterile and do not produce seeds, and secondly because the few that do produce seeds don't "come true", ie the flower of the seedling is not like the flower of the parent.
• Water Cannas These are a distinct type of floral canna which are intended for growing in ponds with the roots totally immersed in water. They were bred by the Longwood Gardens in Pensylvania, USA, and the parentage includes C. glauca which is found in shallow water. They are all tall, around 2 meters, with narrow lance-shaped glaucous foliage. The flowers are very attractive, but rather spidery. There are 4 varieties, all named after ships: 'Ra' (yellow), 'Erebus' (pink), 'Endeavour' (red), 'Taney' (orange). They should be propagated by division because the rhizomes are small and do not over-winter well if allowed to go dormant. They produce seeds, but the seeds do not come true. It is an enigma that Water Cannas can equally well be grown in the garden border, and that most other cannas can also be grown in water. The name rather identifies a tall narrow glaucous plant with attractive spidery flowers.
• Takii Tropical Series This is another group of floral cannas that deserves special mention. This series is bred and marketed by Takii of Japan. Unusual for cannas, they are grown from seed, and they do "come true". They are all short, about 0.5 meters, and flower in around 90 to 120 says from sowing the seed. The seed is supplied pre-scarified. The seeds germinate in about 1 week. We find the best results are to sow the seeds in wet compost at a temperature of at least 30C. They should be grown in rich compost, well watered, and not allowed to become pot-bound. There are 6 varieties: Rose, Yellow, Red, Salmon, White, Bronze/scarlet.
• Foliage Varieties These are cannas which are grown for foliage and not flowers. Often they are giant plants, over 2 meters tall. They make a splendid display in a stately home or park situation.
• Species Some of the original wild species are very garden-worthy, and make attractive and interesting additions to the garden.

To read more about the different types and groups of cannas, see the Canna Wiki pages. Canna Wikipedia pages.

QUALITIES

Cannas have some special and very desirable qualities as garden plants.

• They produce a lot of flowers and have a very long flowering season, from the end of June until mid October.
• They can tolerate any kind of soil: acid, alkaline, sandy, clay, chalk, (but it must be rich).
• They are happy in full sun or shade.
• They can tolerate extended periods of drought, yet they are quite happy even growing standing in water, or even totally immersed in water.
• They do not need staking and are never blown over.
• They are not much troubled by animal or insect pests or slugs.

Hence cannas require very little attention during the growing season. They are "plant and forget".

In case this sounds too good to be true, they do have some disadvantages. In particular, they are vulnerable to a type of virus disease which has decimated cannas during the past 10 years, and so you need to be very careful where you acquire your stock. See www.canna-virus.org.uk

APPLICATIONS IN HORTICULTURE

Cannas are majestic and striking plants. Their giant foliage and beautiful flowers are qualities that few other plants posess. But they are also gutsy and robust plants that require little attention.

For these reasons they have long been popular in public parks and the gardens of stately homes. In such situations they can be used as mass plantings in borders, and as spot plants in flower beds. They have also long been popular in town centre municipal plantings where they often feature in traffic schemes (Roundabouts, dual carriageways). In town centres they are often grown in street-furniture planters and tubs.

These qualities can also find application in private gardens. They are useful to provide an exotic touch to flower borders. But they can equally be grown in planters and tubs.