Canna L.

Scientific Description

Common name. Cannas. Family Cannaceae.

Habit and leaf form. Herbs. Perennial. Leaves cauline. Plants with neither basal nor terminal concentrations of leaves. Young stems cylindrical (terete). To 0.5–5 m high; rhizomatous. Helophytic, or mesophytic. Leaves medium-sized to large; alternate; spiral; more or less petiolate; sheathing. Leaf sheaths with free margins. Leaves simple; epulvinate. Leaf blades entire; flat, or rolled; linear, or lanceolate, or oblanceolate; broadly elliptic to oblong; pinnately veined (with parallel-convergent laterals); without cross-venules; attenuate at the base. Leaf blade margins entire; flat. Vernation convolute. Vegetative anatomy. Plants with silica bodies (these internal, in association with the vascular bundles). Leaf anatomy. Guard-cells not ‘grass type’. Hairs absent. Extra-floral nectaries absent. Stem anatomy. Secondary thickening absent.

Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite. Floral nectaries present. Nectar secretion from the gynoecium (from septal nectaries). Entomophilous. Pollination mechanism conspicuously specialized (pollen is shed on the style in the bud, and later insects alighting on the labellum touch first the terminal stigma, then the pollen).

Inflorescence and flower features. Flowers aggregated in ‘inflorescences’; in spikes, or in panicles (thyrses). The terminal inflorescence unit cymose. Inflorescences scapiflorous, or not scapiflorous; terminal; spikes or thyrses, usually composed of 2-flowered cincinni; pseudanthial (in that the pairs of homodromous, asymmetric flowers are mirror images of one another). Flowers shortly pedicellate, or sessile, or subsessile; bracteate (the bracts usually green and fairly inconspicuous, often small); bracteolate (with a bracteole to the left of one flower, and to the right of the other (behind the one or the other of the two lateral sepals), in each flower pair); very irregular; asymmetric (obliquely orientated, with no clearly median organs). The floral asymmetry involving the perianth and involving the androecium. Flowers fundamentally 3 merous (but with the androecium modified); partially acyclic. The perianth acyclic (the calyx spiral). Perigone tube absent (in that the sepals are free, the tube being derived from corolla and androecium). Free hypanthium made up of the united base of the inner perianth segments, stamens, staminodes and the style. Perianth with distinct calyx and corolla, or of ‘tepals’; 6; isomerous; if considered not resolved into calyx and corolla, more or less petaloid; bract-like; different in the two whorls (or rather, in the two series:the outer members (sepals) greenish or purplish and subpetaloid, smaller); green and yellow, or green and red, or red and yellow, or purple and red (outer members greenish or purplish, inner members yellow or red). Calyx present; 3; 1 -whorled; polysepalous; green, or purple; persistent. Corolla present; 3; 1 -whorled; gamopetalous (into a tube, along with the stamen and staminodes); unequal but not bilabiate (one member often shorter than the other two); yellow, or red. Androecial members definite in number. Androecium (2–)4(–5) (the member across the flower from the inner median tepal always lacking). Androecial members adnate (to the tube); markedly unequal; coherent (shortly connate at the base); (theoretically) 2 -whorled. Androecium including staminodes. Staminodes (1–)3(–4) (with at least one staminodal member of the inner androecial whorl, wider than the others and sometimes called the ‘labellum’, always being represented); petaloid (more conspicuous than the true perianth). Stamens 1 (the median (posterior) member of the inner whorl); reduced in number relative to the adjacent perianth; oppositiperianthial (the single half-anthered stamen being opposite the inner median (posterior) tepal); petaloid (the single fertile stamen bearing only one half-anther, one one edge and often far below the apex). Anthers (or rather, the half-anther) adnate; dehiscing via longitudinal slits; introrse; unilocular; bisporangiate. Pollen shed as single grains. Gynoecium 3 carpelled. The pistil 3 celled. Gynoecium partly petaloid (the style being straight, flat and fleshy-petaloid). Carpels isomerous with the perianth. Gynoecium syncarpous; eu-syncarpous; inferior. Ovary plurilocular; 3 locular. The ‘odd’ carpel anterior. Gynoecium stylate. Styles 1; apical. Stigmas 1. Placentation axile. Ovules 20–50 per locule (‘many’); arillate, or non-arillate (depending on interpretation of funicular structures); anatropous.

Fruit and seed features. Fruit non-fleshy; dehiscent; a capsule (usually warty). Capsules opening by collapse of the pericarp. Fruit 3 celled. Seeds thinly endospermic (the endosperm consisting of a thin, starchy layer). Perisperm present (surrounding the endosperm). Seeds wingless. Embryo well differentiated. Cotyledons 1. Embryo straight. Testa operculate.

Geography, cytology, number of species. World distribution: West Indies and Central America. 55 species.

Economic uses, etc. Ornamental hybrids (C. ‘generalis’) are among the most widely grown tropical bedding plants.

Etymology. From the Greek for "a reed".