Dahlia imperialis

Dahlia imperialis, or bell tree dahlia, is a large flowering plant of the family Asteraceae, native to the Americas.

Description
Growing between 8–10 m tall, it is a herbaceous perennial, rapidly growing in springtime from its tuber, after a dormant winter period (which may be brief in mild climates). From its underground base, the plant will begin sending up hollow, cane-like, 4-sided stems with swollen nodes and large, tripinnate leaves; foliage near the ground is quickly shed. The pendant or nodding flowerheads are 7.5–15 cm across, with ray florets, typically a lavender or mauvish-pink in colour.

This species is fast-growing, the growth spurt being linked to shorter daylight hours; the tree dahlia usually comes into flower in autumn, before the risk of frost. Propagation is by seed or by stem cuttings, around 30 cm long and having at least two nodes, laid horizontally about 5–10 cm under the soil; top-dressing with pea gravel, decomposed granite, or grit is optional but helpful for moisture retention, erosion control and additional drainage.

Taxonomy
After some Dahlia species were brought from Mexico to Europe in the 16th century, D. imperialis was first described in 1863 by Benedikt Roezl (1823–1885), the great Czech orchid collector and traveller who, ten years later (in 1872–73), embarked on a plant odyssey through the Americas.

Distribution and habitat
It is native to Mexico, Belize, Guatemala, Honduras, El Salvador, Nicaragua, Costa Rica, Panama and south into Colombia and Ecuador. It is a plant of the uplands, mainly found in the foothills of subtropical or tropical mountains (above the humidity of the lower forests), at elevations around 1500 - 1700 m.

Uses
Many tuberous dahlia can be prepared and consumed like potatoes or cooked carrots. Additionally, the petals can be eaten on green salads or soups, and tree dahlia leaves are used as a dietary supplement by the Q'eqchi' people of San Pedro Carchá, Alta Verapaz, Guatemala.