Canna (plant)
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19 classified species, see list below |
Canna (Canna or Canna lily although not a true lily) is a genus of nineteen species of flowering plants, the only genus in the family Cannaceae. The closest living relations to cannas are the other plant families of the order Zingiberales, that is the gingers, bananas, marantas, heliconiaa, strelitzias, etc.
The species have large, attractive foliage and horticulturists have turned it into a large, brash, bright and sometimes gaudy, garden plant. In addition, it is one of the world's richest starch sources, and is an agricultural plant.
Although a plant of the tropics, most cultivars have been developed in temperate climates and are easy to grow in most countries of the world as long as they can enjoy about 6 hours average sunlight during the summer. See the Canna cultivar gallery for photographs of Canna cultivars.
The name Canna originates from the Celtic word for a cane or reed [Johnsons 1856, Chaté 1866].
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[edit] Botany
The plants are large tropical and subtropical perennial herbs with a rhizomatous rootstock. The broad, flat, alternate leaves, that are such a feature of this plant, grow out of a stem in a long narrow roll and then unfurl. The leaves are typically solid green but some cultivars have glaucose, brownish, maroon, or even variegated leaves.
The three sepals and three petals are seldom noticed, they are small and hidden under extravagant stamens. What appear to be petals are the highly modified stamens or staminodes. The staminodes number (1–) 3 (–4) (with at least one staminodal member called the labellum, always being represented. A specialised staminode, the stamen, bears pollen from a half-anther. A somewhat narrower, 'petal' is the pistil which is connected down to a three-chambered ovary.
The flowers are typically red, orange, or yellow or any combination of those coloors, and are aggregated in inflorescences; in spikes, or in panicles (thyrses). Although gardeners enjoy these odd flowers, nature really intended them to attract pollinators collecting nectar, such as bees, hummingbirds and bats. The pollination mechanism is conspicuously specialized (pollen is shed on the style while still in the bud, and later pollinators alight on the labellum and touch first the terminal stigma, then the pollen).
The wild species often grow to 2-3+ meters but there is a wide variation in size among cultivated plants; numerous cultivars have been selected for smaller stature.
Canna grow from swollen roots, correctly known as rhizomes, which store starch, and this is the main attraction of the plant to agriculture, having the largest starch particles of all plants.
Canna is the only member of the monocot family in which Physical Dormancy of seed is known to occur, due to its hard, impenetrable seed covering.
[edit] Range
The genus is native to tropical and subtropical regions of the New World, from the southern United States (southern South Carolina west to southern Texas) and south to northern Argentina.
Although all cannas are native to the New World, they have followed mankind's journey's of discovery and some species are cultivated and naturalized in most tropical and sub-tropical regions.
Canna cultivars are grown in most countries, even those with territory above the Arctic circle, which have short summers but long days, and the rapid growth rate of Cannas makes them a feasible gardening plant, as long as they get their 6 hours of sunlight each day during the growing season and are protected from the cold of winter.
[edit] Origins
- "The first Cannas introduced to Europe were C. indica L., and although they all came from the East Indies, they originated from the American continent. Charles de l'Ecluse, who first described and sketched C. indica in his Histoire des plantes rare observées en Espagne, published in 1576, indicates this origin, and states that it was given the name of indica, not because the plant is from India, in Asia, but because this species was originally transported from America: "Quia ex America primum delata sit"; and at that time, one described the tropical areas of that part of the globe as the Western Indies; English speakers still call them the West Indies.
- Much later, in 1658, Pison made reference, in his Histoire naturelle du Brésil, to another species which he documented under the vulgar name of 'Albara' and 'Pacivira', and which resided, he said, in the shaded and damp places, between the tropics; this species is Canna angustifolia L., (later reclassified as C. glauca L. by taxonomists).
- Without exception, all Canna species that have been introduced into Europe can be traced back to the American continent, and it can be asserted with confidence that Canna is solely an American genus. If Asia and Africa provided some of the early introductions, they were only varieties resulting from C. indica and C. glauca cultivars that have grown for a long time in India and Africa, but not from species growing in a spontaneous state.
- The penultimate argument is that it is certain, as it is pointed out by Lamarck, in his Botanical Encyclelopédie, that "Cannas were unknown to the ancients, and that it is only after the discovery of the New World, that they made their appearance in Europe; whereas if the soils of India or Africa had produced some of them, they would not have waited until the 1860’s, to make an entry into the European gardens."
- The final argument is that Canna seeds have never been discovered by archeologists in the Old World, and the hard shells of Canna would have ensured that some would have survived in the right conditions.
[edit] Uses
- Some species and many cultivars are widely grown in the garden in temperate and sub-tropical regions. Sometimes they may also be grown as potted plants. A large number of ornamental cultivars have been developed. They can be used in herbaceous borders, tropical plantings, and as a patio or decking plant.
- Internationally cannas are one of the most popular garden plants and a large horticultural industry depends on the plant.
- The canna rhizome of is rich in starch, and it has many uses in agriculture. All of the plant has commercial value, rhizomes for starch (consumption by humans and livestock), stems and foliage for animal fodder, young shoots as a vegetable and young seeds as an addition to tortillas.
- Agricultural Cannas have the potential to be a rich producer of biofuels because of its outstanding starch production, and ability to thrive in temperate climates as well as the tropics. This is a young area of research and we have to wait for research results before commenting further on this use.
- Cannas (particularly C. indica) are sometimes known as "Indian Shot", as their seeds are small, round, and hard like bird shot. The seeds are used as pearls in jewelry.
- The seeds are used as the mobile elements of the kayamb, a musical instrument from Réunion, as well as the hosho, a gourd rattle from Zimbabwe, where the seeds are known as "hota" seeds.
- In remoter regions of India, cannas are fermented to produce alcohol.
- Cannas are used to extract many undesirable pollutants in a wetland environment as it has a high tolerance to contaminants.
[edit] Classification of Cannas
[edit] Species
In the last three decades of the 20th century, Canna species have been categorised by two different taxonomists, Professor Paul Maas and his wife, Dr. Hiltje Maas, from Holland and Dr. Nobuyuki Tanaka from Japan. Both reduced the number of species from the 50-100 that had been accepted previously, and assigned most to being synonyms. Inevitably, there are some differences in their categorisations, and the individual articles on the species describes those differences.
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[edit] Horticultural Cannas
See the Canna (Plant) Gallery for photographs of Canna cultivars.
Cannas became very popular in Victorian times as a garden plant and were grown widely in France, Germany, Hungary, India, Italy, the United Kingdom, and the USA and have recently experienced a renewed interest and revival in popularity. There were once many hundreds of cultivars but many of these are now extinct.
In recent years many new cultivars have been created, but the genus suffers from having many synonyms for many popular ones. Most of the synonyms were created by plant growers attempting to market their stock. Research has accumulated over 2,000 cultivar names, however, many of these are simply synonyms.
- Canna x annaei André.
- Canna x hortensis Guill.
The first hybridisation of Cannas was performed in 1848 by a gentleman gardener, Monsieur Théodore Année of Passy, France. He was rapidly joined by many other enthusiasts and professional horticulturalists as Canna hybrids enjoyed rapid popularity in France. Amongst the professionals was the rose breeder Monsieur Pierre-Antoine-Marie Crozy (1831-1903) of Avoux & Crozy, La Guillotière, Lyon, France, who first started hybridising Cannas in 1862 and continued introducing new canna cultivars at a rapid rate until his death in 1903, giving his name to a whole new group of floriferous Canna cultivars. Crozy aîné (French for "elder"), as he was universally known, was succeeded by his son, Michel Crozy (1871-1908).
- Canna × generalis L.H.Bailey
- Canna × orchiodes L.H.Bailey
In the early 1900's, Professor Liberty Hyde Bailey defined, in detail, two garden species (C. x generalis and C. x orchiodes) to categorise the floriferous Cannas being grown at that time, namely the Crozy hybrids and the ‘orchid-like’ hybrids introduced by Carl Ludwig Sprenger in Italy and Luther Burbank in the USA, at about the same time (1894). The definition was based on the genotype, rather than the phenotype, of the two cultivar groups. Inevitably, over time those two floriferous groups were interbred, the distinctions became blurred and overlapped, and the Bailey species names became redundant. Pseudo-species names are now deprecated by the International Code of Nomenclature for Cultivated Plants which, instead, provides Cultivar Groups for categorising cultivars.
[edit] Agricultural Cannas
Canna achira is a generic term used to describe the cannas that have been selectively bred for agricultural purposes, normally derived from C. indica 'Edulis'. It is grown especially for its edible rootstock from which arrowroot starch is obtained, but the leaves and young seed are also edible, and achira was once a staple foodcrop in Peru and Ecuador. Little explored, is the possibility of its rich starch content being used to produce biofuel.
- Farming Varieties
There are some named agricultural varieties, and published comparative studies have involved:
- C. 'Thai-purple'
- C. 'Thai-green'
- C. 'Japanese Green'
Many more traditional varieties exist world-wide, they have all involved human selection and so are classified as agricultural cultivars. Traditionally, Canna indica 'Edulis' has always been regarded as the variety mainly grown for food in South America, but there is little scientific evidence to substantiate that claim.
In the Andes, the rhizome can be harvested within 6 months from planting out and the yields range from 13 - 85 tonnes per hectare, with 22 - 50 tonnes being average, though larger yields are obtained after 8 - 10 months.
Most cultivated forms do not produce fertile seed. There are also sterile triploid forms, these contain a significantly higher proportion of starch, though their cropping potential is not known.
- Animal fodder
The rhizomes and leaves are good fodder for cattle and pigs and it is grown for this purpose in Hawaii, where it is harvested 4-8 months after planting.
- Human consumption
Canna is still grown for human consumption in the Andes and also in Vietnam and southern China, where the starch is used to make cellophane noodles.
- Edible qualities
Rootstock - actually a rhizome, this can be eaten either raw or cooked. It is the source of canna starch which is used as an arrowroot. The arrowroot is obtained by rasping the rhizome to a pulp, then washing and straining to get rid of the fibres. This starch is very digestible. The very young rhizomes can also be eaten cooked, they are sweet but fibrousy. The rhizome can be very large, sometimes as long as a person's forearm. In Peru the rhizomes are baked for up to 12 hours by which time they become a white, translucent, fibrous and somewhat mucilaginous mass with a sweetish taste. The starch is in very large grains, about three times the size of potato starch grains, and can be seen with the naked eye. This starch is easily separated from the fibre of the rhizome. The rhizomes contain about 25% starch. The dry matter contains about 75 - 80% starch, 6 - 14% sugar, 1 - 3% protein, it is high in potassium, low in calcium and phosphorus.
Young shoots - these can be cooked and eaten as a green vegetable and are quite nutritious, containing at least 10% protein.
Seeds - the immature seeds are cooked in fat in tortillas.
[edit] Cultivation
Cannas grow best in full sun with moderate water in well-drained rich or sandy soil. Cannas grow from perennial rhizomes but are frequently grown as annuals in temperate zones for an exotic or tropical look in the garden.
The rhizomes are marginally cold hardy but may rot if left unprotected in freezing conditions. In areas which go below about −10 °C in the winter, the rhizomes can be dug up before freezing and stored in a protected area (above +7 °C) for replanting in the spring. Otherwise, it is recommended that Cannas are protected by a thick layer of mulch overwinter.
[edit] Pests
Cannas are largely free of pests but the plants sometimes fall victim to Canna leaf rollers, or Brazilian skippers, the larval stage of a butterfly that cuts the leaves and rolls them over to live inside while pupating (the lesser canna leaf roller will sew the leaves shut before they can unfurl). Affected leaves can be cut off and destroyed or unrolled and cleaned (removing the caterpillar), though some gardeners prefer to use Bacillus thuringiensis, insecticidal soap, or the chemical malathion to kill the pests. In areas with a freezing winter the leaf roller is not typically a pest.
Slugs are fond of cannas and can leave large holes in the leaves, preferring the tender young leaves that have not yet unfurled.
[edit] Disease
Canna are remarkably free of disease, compared to many genus, however, there are some problems which have been exacerbated in recent years by growers ignoring disease and selling packaged rhizomes badly affected by virus. The years 2004 and 2005 have seen a shortage of Canna on sale, and the industry appears to be attempting to remove this problem from the genus.
- Canna Rust
Cannas may also fall victim to canna rust, a fungus resulting in orange spots on the plant's leaves. Rust infestation is facilitated by overmoist soil.
- Canna Virus
Cannas are also susceptible to certain plant viruses, which may result in spotted or streaked leaves, in a mild form, but can finally result in stunted growth and twisted and distorted blooms and foliage. In the United Kingdom, the RHS laboratory at Wisley confirm that they have identified:
- Canna yellow mottle badnavirus (CYMV) infecting canna species.
- Bean yellow mosaic virus (BYMV) infecting cannas, gladiolus, freesia and many legumes.
- Tomato aspermy virus, also affects cannas and many other plants in other countries, but it has not reported affecting cannas in the UK.
- Reports from other countries are claiming that there are 5 viruses involved in all. This has not been confirmed.
Overall, very little is known about Canna virus, but the following points are generally accepted:
- It manifests itself in rust coloured streaks or mottled markings on the leaves and in colour breaks on the flowers.
- Sometimes leaves are slightly distorted and puckered.
- Like many plants under stress, affected cannas will flower very early in the season and before the plant is full height.
- Over the years the canna will loose vigour and become increasingly unsightly.
- It is spread by aphids and other sap sucking insects.
- At one time it was thought that Cannas may have the ability to outgrow the virus, but that is not the case.
- Most authorities advise to burn all affected cannas and start again.
- Keep any new introductions well away from potentially infected stock.
Virus causes colour breaks in flowers |
CYMV infected foliage |
BYMV infected foliage |
[edit] Propagation of Canna
[edit] Sexual propagation
Seeds are produced from sexual reproduction, involving the transfer of pollen from the stamen of the pollen parent onto the stigma of the seed parent. In the case of Canna, the same plant can usually play the roles of both pollen and seed parents, technically referred to as a hermaphrodite. However, the cultivars of the Italian Group are almost always seed sterile and their pollen has a low fertility level. Mutations are almost always totally sterile.
- Pollination
The species are capable of self-pollination, but most cultivars require an outside pollinator. All cannas produce nectar and therefore attract nectar consuming insects, bats and small birds that act as the transfer agent, spreading pollen between stamens and stigmas, on the same or different inflorescence.
- Genetic changes
Since genetic recombination has occurred a cultivar grown from seed will have different characteristics to its parent(s) and thus should never be given a parent’s name. The wild species have evolved in the absence of other Canna genes and are deemed to be ‘true to type’ when the parents are of the same species. In the latter case there is still a degree of variance, producing various varieties or minor forms (forma). In particular, the species C. indica is an aggregate species, having many different and extreme varieties and forma ranging from the giant to miniature, from large foliage to small foliage, both green and dark foliage and many different coloured blooms, red, orange, pink, and yellow and combinations of those colours.
[edit] Asexual propagation
- Division of plant parts
Outside of a laboratory, only rhizome division is feasible for the gardener. This is using material from a single parent, and as there is no exchange of genetic material such vegetative propagation methods almost always produce plants that are identical to the parent. After a summer’s growth the horticultural Canna can be separated into typically four or five separate smaller rhizomes, each with a growing nodal point (‘growing eye’). Without the growing point, which is composed of meristem material, the rhizome will not grow.
- Micropropagation
Micropropagation, invitro culture is the practice of rapidly multiplying stock plant material to produce a large number of progeny plants, using modern plant tissue culture methods. Many commercial organisations have attempted to produce Canna this way, and specifically the “Island Series” of Cannas was introduced for mass production using this technique. However, Cannas have a reputation of being difficult micropropagation specimens.
Note - if such a method is employed on specimens infected with Canna Virus it is possible to use the growing tip as the explant, this is composed of meristem material and has a very high probability of being uncontaminated. In this way, healthy stock can be reclaimed from virus contaminated plants.
[edit] References
- Bailey, L.H. - Canna x generalis. Hortus, 118 (1930); cf. Standley & Steyerm. in Fieldiana, Bot., xxiv. III.204 (1952).
- Bailey, L.H. - Canna x orchiodes. Gentes Herb. (Ithaca), 1 (3): 120 (1923).
- Chaté, E. - Le Canna, 1866.
- de l'Ecluse, Charles - Histoire des plantes rare observées en Espagne, 1576.
- Johnson's Gardner's Dictionary, 1856.
- Khoshoo, T.N. & Guha, I - Origin and Evolution of Cultivated Cannas.
- Lamarck, Jean-Baptiste - Botanical Encyclelopédie.
- Pison - Histoire naturelle du Brésil, 1658.
- Segeren, W & Maas, PJM - The genus Canna in northern South America (1971), Acta Botanica Neerlandica. 20(6): 663-680.
- Tanaka, N. 2001. Taxonomic revision of the family Cannaceae in the New World and Asia. Makinoa ser. 2, 1:34–43.
[edit] External links
- Cannaceae in Flora of North America
- Canna × generalis from Floridata
- Canna indica: Indian Shot
- "Colorful Cannas" By Cynthia W. Mueller, from the November-December 2001 issue of Horticulture Update
- International Society for Horticultural Science (ISHS).
- PRINCE, LINDA M.* and W. JOHN KRESS. Smithsonian Institution, NMNH - Botany, MRC-166, Washington, DC 20560-0166. - Species boundaries in Canna (Cannaceae): evidence from nuclear ITS DNA sequence data.
- Reappraisal of Edible Canna as a High-Value Starch Crop in Vietnam
- Royal General Bulbgrowers' Association (KAVB), the ICRA for the Canna genus.
[edit] See also
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