[Smart Farmers] Named after "Beauty"! Uncovering the secrets of the "civil and military" canna that migrated from the tropics

Canna is a perennial bulbous flower of the genus Canna in the family Cannaceae. It is named for its banana-like leaves and large, colorful flowers. It is an introduced species a long time ago.
Before the Tang and Song dynasties, only red flowers were called "red bananas"; and after the Ming and Qing dynasties, flowers of other colors were cultivated and called "cannas". Modern varieties have not only beautiful corollas, but also "mutated" leaves, with white or light pink spots and patterns, and even bright purple leaves, which are very beautiful.

The straight "stem" of canna is actually a pseudostem formed by multiple leaf sheaths arranged closely together, which makes the plant, which is originally a delicate herb, tall and strong. Most varieties can grow to about 2 meters. Its large leaves are shaped like bananas, smooth and covered with waxy white powder. At first glance, it looks shiny green, and it is very tropical when planted in northern courtyards.

We usually think that the most colorful and eye-catching petals are the most unique part of canna, but in fact they are the staminodes. So where are the real petals? The real petals are the three thin lanceolate parts that are like calyx and wrapped outside the staminodes. They are light in color and have low ornamental value.

There is only one fertile stamen that has not degenerated, and it looks like a petal torn in half, with the anther attached to its side. Hidden under the petal-shaped stamen is a "crescent scimitar", which is a variation of the pistil. The thin and flat "blade" is actually the style, and nectar is hidden deep in the corolla under the style. Friends who live in the south may have memories of stealing canna "scimitars" to suck nectar when they were young.

Canna can grow and bloom all year round in its place of origin or tropical areas with suitable conditions. After coming to China, it blooms continuously from June to before the Descent of Frost in various places, and the total flowering period is very long. The season when it blooms bright red is the hot summer with few flowers. Canna can greatly enrich the color of the courtyard in summer.

A veritable "plant doctor"

In addition to the pleasing flowers, the underground rhizomes of canna are well-developed, with many branches and blocky shapes, a bit like lotus roots or taro, which store a lot of nutrients. Vermicelli made from these rhizomes are especially suitable for the elderly, the weak and children to strengthen their physical fitness. Some places have now developed some special edible canna varieties, which are used to cook the rhizomes or make wine.

In addition, the rhizome can be used as medicine to treat hypertension, angina pectoris, acute infectious hepatitis, etc.

A “Live” Monitor of Air Pollutants

Canna can absorb harmful substances such as sulfur dioxide, carbon dioxide, and hydrogen chloride from head to toe, which can purify the air and protect the environment. When the concentration of toxic gases is slightly high, its leaves are easily damaged, but after being damaged, they can quickly produce new leaves and resume growth, which is a manifestation of good resistance. At the same time, because the leaves are sensitive to toxic gases, they are called "living" monitors of atmospheric pollutants.

Canna also has many economic values: for example, the stem and leaf fibers can be used to make paper, weave sacks, make artificial cotton, and twist ropes; the beautiful flowers also have the function of stopping bleeding, and can be used to treat wounds and other external bleeding.

Seeds are the arsenal for making bullets

After the canna flower fades, the ovary develops larger, and the fruit is round and densely covered with soft warty thorns, and inside are large black seeds. These black seeds are very hard, and during the American colonial war, the local indigenous people used these black seeds as a substitute for the lack of bullets. They made many contributions in resisting the invasion of white people and were called "Indian bullets".

Immigrants from the tropics can also grow tenaciously

Canna is native to tropical regions such as America and India, and has "migrated" to most areas of China. Because it is not cold-resistant, its flowers and leaves will wither after frost. In the middle and lower reaches of the Yangtze River, the above-ground parts of canna wither in winter, and the underground rhizomes can overwinter in the open field. Relying on the nutrients stored in these rhizomes, new leaves and flowers can sprout from the underground rhizomes again in the spring of the following year; while in the areas north of the Yangtze River, the underground rhizomes of canna need to be dug out after the frost in late autumn, wrapped in a thick layer of wet sand, and stored indoors for overwintering, and then replanted in large outdoor fields the following spring.

Canna can be sown or propagated by dividing rhizomes. Rhizome propagation is to dig out the old rhizomes before the rhizomes sprout in early spring from March to April, trim off the rotten parts, and cut them into blocks; the incision should be smooth, and the cut surface should be coated with plant ash or charcoal powder to prevent wound infection. Keep 2-3 buds with fibrous roots on each rhizome, then plant the divided rhizome blocks in the soil about 10cm deep, keep the spacing (the distance between rhizome blocks) at 40cm-50cm, cover with soil and water enough. When the seedlings sprouting from the rhizome blocks grow to 5-6 green leaves, apply decomposed fertilizer to the soil around the roots once, and it will bloom that year.

Scientific review: Hu Dongmei, Senior Laboratory Technician, College of Biological Sciences and Technology, Beijing Forestry University

Author: Wang Jue, Associate Professor, Beijing Forestry University

Hand-drawn illustrations: Xia Xinyi, student of the Middle School Affiliated to University of Science and Technology Beijing

Editor: Wu Yuetong

Proofreader: Yan Shuo (internship)