Canna indica, commonly known as Indian shot, African arrowroot, edible canna, purple arrowroot, Sierra Leone arrowroot, is a plant species in the family Cannaceae. It is native to the Americas and naturalized elsewhere. The edible rhizomes are a source of starch.
Description Canna indica is a perennial growing to between , depending on the variety. It is hardy to zone 10 and is frost tender. The plants form an upright, unbranched stem or the overlapping leaf sheaths form a pseudo trunk.Funk, VA, PE Berry, S. Alexander, TH Hollowell & CL Kelloff. 2007. Checklist of the Plants of the Guiana Shield (Venezuela: Amazonas, Bolivar, Delta Amacuro, Guyana, Surinam, French Guiana). Contr. US Natl. Herb. 55: 1-584.
It forms branched rhizomes longFAO, "Canna edulis ", accessed 23 Feb 2016. that are divided into bulbous segments and covered in two lines by pale green or purple flaky leaves. The surface of the rhizome is carved by transverse grooves, which mark the base of scales that cover it. From the lower part white and apex rootlets emerge, where there are numerous buds, the leaves sprout, the floral stem and the stems.Flora of China Editorial Committee. 2000. Flora of China (Flagellariaceae through Marantaceae). 24: 1-431. In CY Wu, PH Raven & DY Hong (eds.) Fl. China. Science Press & Missouri Botanical Garden Press, Beijing & St. Louis. The very large grains of starch can supposedly be seen with the naked eye.
The alternate and spiral or two-line arranged, very large, simple leaves are divided into leaf sheaths, short petioles and leaf blades. The leaf blade has a length of and a width of . The parallel leaf veins arise from the midrib (not typical of monocots). The leaves are broad, green or violet green, with elliptical sheets, which can measure 30 to 60 cm long and 10 to 25 cm wide, with the base obtuse or narrowly cuneate and the apex is shortly acuminate or sharp.
Flowers
The flowers are hermaphrodite.Johnson's Gardeners Dictionary, 1856Chaté, E. (1867) Le Canna, son histoire, son culture. Libraire Centrale d'Agriculture et de Jardinage.Khoshoo, T.N. & Guha, I. - Origin and Evolution of Cultivated Cannas. Vikas Publishing House.Cooke, Ian, 2001. The Gardener's Guide to Growing cannas, Timber Press. The mostly large flowers are zygomorphic and threefold. On pedicels, they are long, red or yellow-orange, except in some cultivars, long, with the sepals being closely triangular, long and the petals erect, 4–6.5 cm long. The tube is 1.5–2 cm long.
The bracts are designed differently. The three free sepals are usually green. The three petals are green or have depending on the variety shades of yellow about orange and red to pink. The base of the petals is fused with the staminodien to a stamen column. There are two circles, each with originally three stamens present. The petals and staminodes are usually yellow to red. The three carpels are at a constant under (syncarp) ovary adherent which has a soft-spiky surface and many central-angle-constant ovules. The pollen is deposited on the abaxial (off-axis) surface of the stylus.
The pollination mechanism is very specialised and the pollination is done by insects. The insects pick up the pollen from the flattened style. In their natural habitat, blooming occurs in the months of August to October. The fruits are ellipsoid capsules to globose, warty, 1.5 to 3 cm long, chestnut coloured, with a large amount of black and very hard seeds.Nobuyuki Tanaka: "Taxonomic revision of the Cannaceae family in the New World and Asia". In: Makinoa, 1, 2001, pp. 1–74.
Seeds
The seeds are small, globular, black pellets, hard and dense enough to sink in water. They resemble shotgun pellets giving rise to the plant's common name of Indian shot.Seeds fired from a shotgun, BBC, 9 February 2012. Retrieved 27 August 2012. They are hard enough to shoot through wood and still survive and later germinate.
Taxonomy
In the last three decades of the 20th century, Canna species have been categorised by two different taxonomists, Paulus Johannes Maria Maas from the Netherlands and Nobuyuki Tanaka from Japan. Maas regards C. coccinea, C. compacta, C. discolor, C. patens and C. speciosa as synonyms or varieties of C. indica, while Tanaka recognises several additional varieties of C. indica.
Canna indica var. indica L. A medium sized species; green foliage, oblong shaped, spreading habit; triangular flower stems, coloured green; spikes of flowers are erect, self-coloured red, staminodes are long and narrow, edges regular, petals red, partial self-cleaning; fertile both ways, self-pollinating and also true to type, capsules globose; rhizomes are thick, up to 3 cm in diameter, coloured purple; tillering is prolific. Introduced by Linnaeus.Tanaka, N. 2001. Taxonomic revision of the family Cannaceae in the New World and Asia. Makinoa ser. 2, 1:34–43. Canna indica var. flava (Roscoe ex Baker) Nb. Tanaka Yellow bloom. Many plants previously offered as C. lutea fall into this subspecies. Canna indica var. maculata (Hook) Nb. Tanaka A medium sized species; green foliage, ovoid shaped, branching habit; spikes of flowers are erect, yellow with red spots, staminodes are long and narrow, edges regular, petals green, fully self-cleaning, low bloomer; fertile both ways, self-pollinating and also true to type, capsules globose; rhizomes are thick, up to 3 cm in diameter, coloured white and pink; tillering is average. Introduced by Hook.. Many plants previously offered as C. lutea fall into this subspecies. Canna indica var. sanctae rosea (Kraenzl) Nb. Tanaka A small species; green foliage, oval shaped, white margin, branching habit; spikes of flowers are erect, self-coloured pink, staminodes are long and narrow, edges regular, labellum is pink, stamen is pink, style is pink, petals red with farina, fully self-cleaning; fertile both ways, self-pollinating and also true to type, capsules ellipsoid; rhizomes are thick, up to 3 cm in diameter, coloured white and pink; tillering is prolific. Canna indica var. warszewiczii (A.Dietr.) Nb.Tanaka This variety is distinguishable from C. indica var. indica by having purple-red-margined leaves, purple-red fruits and slightly corm-like thickened terrestrial stem at the base. Additionally to this, there are normally two staminodes, recurved backwards, and the stamen is often strongly reflexed at the apex. These characteristics are fairly stable in this taxon. Sometimes, this variety is confused with C. discolor Lindl., from which it differs in much smaller, deep-red coloured flowers, short and slender rhizomes and chromosome numbers (2n=27 in C. discolor and 2n=18 in C. indica var. warszewiczii)
John Gilbert Baker recognizes 2 varieties: Canna indica var. napalensis (Wall. ex Bouché) and Canna indica var. orientalis (Roscoe), William Aiton recognizes 2 varieties of Canna indica var. lutea (Mill.) and Canna indica var. rubra, and Eduard August von Regel recognizes one variety of Canna indica var. edwardsii.
Distribution and habitat Canna indica is native to much of South America: Colombia, Venezuela, Ecuador, Peru, Brazil, Uruguay and Argentina as well as the West Indies and Central America.illeen, TJ & TS Schulenberg. 1998. A biological assessment of Noel Kempff Mercado National Park, Bolivia. RAP Working Papers 10: 1–372.
In modern times, it is also naturalized in the southeastern United States (Florida, Texas, Louisiana, and South Carolina), and much of Europe, sub-Saharan Africa, Southeast Asia, and Oceania. C. indica is reportedly naturalized in Austria, Portugal, Spain, Azores, Canary Islands, Cape Verde, Madeira, most of tropical Africa, Ascension Island, St. Helena, Madagascar, China, Japan, Taiwan, the Bonin Islands, India, Nepal, Sri Lanka, Cambodia, Laos, Thailand, Vietnam, Burma, Java, Malaysia, the Philippines, Christmas Island, the Bismarck Archipelago, Norfolk Island, New South Wales, Queensland, Fiji, Tonga, Vanuatu, Kiribati, the Cook Islands, the Society Islands, the Caroline Islands and Hawaii.
Canna can be cultivated from sea level to above sea level, but thrives in temperate, tropical or subtropical mountain climates, between above sea level (in humid tropical climates for higher elevations) at a mean temperature of 14 to 27 °C. The plant prefers a mean annual rainfall between , but it can tolerate 500–5,000 mm per year. Canna prefers light sandy-loamy soils, but can also grow on heavy soils, as far as they are not wet. It is indifferent to soil pH. For seeds to germinate, they must soak in water for two to three days.Idárraga-Piedrahita, A., RDC Ortiz, R. Callejas Posada & M. Merello. (eds.) 2011. Fl. Antioquia: Cat. 2: 9-939. University of Antioquia, Medellín.
Ecology Diseases Cannas suffer from relatively few diseases compared to other species. Nevertheless, some diseases have been recorded to affect C. indica. One of them is Canna rust (Puccinia thaliae), a fungus that causes orange spots on the leaves. In addition, plant viruses occur: Hippeastrum mosaic virus, Tomato aspermy virus, Canna yellow mottle virus and Canna yellow streak virus which can cause mild or strong symptoms from streaked leaves, stunted growth to distorted blooms. Furthermore, there is Botrytis (fungus), a mold that affects the flowers.
Many different Canna varieties exist, and some of them are resistant to a certain type of disease. To prevent mold, the soil should be well-drained without too much soil moisture or stagnating water. To diminish the risk of spreading diseases, dead and infected leaves should be removed.
Pests The canna leaf roller butterfly (Calpodes ethlius) has been seen on Canna plants in the US. It is a caterpillar known as the worst pest for this plant and primarily found in the Southern United States. This pest causes damages by laying its eggs in the bud of developing stalks. To protect the eggs from predators and insecticide, caterpillars use sticky webs to keep the leaves from unfurling. The pupate then feed on the leaves which can lead to losses of yield due to reduced photosynthesis.
The Japanese beetle (Popillia japonica) is another leaf ragging pest with mainly small consequences for Canna plants. This beetle feeds on the part of the leaves between the veins. In its originating region in Japan, it does not cause a lot of damages. However, in the US it has no natural predator and can cause serious damages on Cannas and other plants.
The bird cherry-oat aphid (Rhopalosiphum padi) has been recorded to affect stored rhizomes. Although this pest has not been causing severe damages yet, it can particularly affect plants grown in greenhouses and can be combatted with parasitical wasps. It is a more common pest on cereals.
As an invasive species C. indica has been included in the Global Invasive Species Database and has been declared as invasive in the following places: South Africa where it is categorised as a category 1b Invader in terms of the National Environmental Management: Biodiversity Act (10/2004) list of Alien and Invasive Species which prohibits their cultivation, propagation, translocation and trade, and requires them to be removed and destroyed when found. This is because it competes with and replaces indigenous species, often in waterways and marshy areas. Australia, regarded as a weed in New South Wales and South Eastern Queensland Pacific Islands, where it has been included in the list of plant threats to Pacific ecosystems as a high-risk species