Canna Plant Morphology The Flower

The Canna Plant flower is very exotic. Technically, the flowers are inflorescences (clusters of flowers on a single structure). A single inflorescence forms at the tip of the stalk. The inflorescence elongates throughout the season (racemose) and new florets (individual flowers on an inflorescence) form along the sides of the flower spike (rachis) over a long period of time. Each floret is subtended by a few inconspicuous bracts. The inflorescence may be straight and narrow (a spike) or quite well branched (a panicle or thyrse). This well-branched trait is strongly selected for by breeders as it is showier. The florets are spirally arranged around the flower spike (1/3 phyllotaxy). Some Canna florets open in the morning and look best during the day time, while others are night bloomers whose beauty is waning by the next morning. Canna flowers are pollinated by a variety of organisms. Day-flowering Cannas are pollinated by bees or hummingbirds and night-flowering Cannas are pollinated by moths or bats. In addition to cross pollination, Canna flowers are self-fertile and may pollinate themselves.

Canna florets have sepals and petals like most flowers. However, they are generally small, inconspicuous and not showy. Canna florets have 3 sepals and 3 petals. The showy part of a Canna floret is actually a modified petaloid stamen called a staminode. Staminodes are the large, colorful petals that we see. There are 3 to 5 sterile staminodes and 2 fertile staminodes (rarely 3-4) in each floret. The sterile staminodes are wide and petal-like. The bottom staminode is usually narrower, curved or twisted, and may have a different color pattern than the others. This bottom staminode is called the labellum. The labellum on some cultivars has a very different shape from the other staminodes, but on others it is nearly identical. The center of the floret contains two narrow staminodes that hold the sex organs of the Canna flower. There is one male staminode that produces pollen (usually curved) and one female staminode that contains a pollen-receptive surface called a stigma (usually straight and dagger-like). The fertile staminodes usually have the same color as the infertile staminodes, but not always.

The staminodes are obovate or triangular in shape and may be narrow or wide. Wide staminodes may overlap or fuse together at the base to form a trumpet-like, flared tube. Canna florets tend to be short-lived, lasting only a day or two. New florets open constantly and provide a continual bloom during the season. Cannas will start flowering once the plant has 6 to 9 leaves. In temperate gardens, flowering usually begins in mid-summer and will last until frost. The start date and duration of flowering varies by cultivar. Flowering is more prolific if gardeners remove the old flowers taking care not to damage the flower spike. In a greenhouse, Cannas will generally not flower in the winter due to low light levels, and flowering may be curtailed during extremely hot temperatures.

Cultivated Canna florets are quite large (up to 5 across) and held erect above the plant which make them a prominent focal point for the garden. The flower shape of cultivars varies widely. Staminodes may be narrow and spidery so that they do not overlap at the base. Or they may be wide and round so that they overlap a great deal. The florets may have a round shape, a Cattelya orchid shape, a Gladiolus shape, or a triangular shape. The florets may face downward and dangle in some species but generally are upward or outward facing.

Canna flowers range in color from pale-yellow to orange to blood-red and all shades in between (salmon, apricot, and pink). Many people think that Canna flowers only come in rich, saturated exciting colors like bright-red or yellow. However, there are many pastel shades of pink, primrose yellow, and pale orange. A few cultivars are marketed as being white, but that is not strictly true. The white Cannas usually emerge a very pale yellow and mature to a cream color. There are no true white Cannas in cultivation. Some of the Victorean era Cannas were said to have been pure white, but they have been lost to history and we have no way of verifying these claims. There are no blue or purple Canna flowers.

Canna flowers may be stiped, streaked, spotted or splotched with contasting colors. The most common form is a yellow or orange flower with darker red to brown splotches on it. There are a few picotee cannas that are red with a yellow edge. Occasionally the throat of the flower (where the staminodes overlap) will have a contrasting color. The labellum of the Canna Plant flower may have contrasting spots or stripes on it too.