dahlia

Dahlia is a genus of flowering plants in the family Asteraceae, native to Mexico and Central America. The genus, named by the botanist Antonio José Cavanilles in 1791 to honor the Swedish botanist Anders Dahl, comprises about 40 species of herbaceous, tuberous perennials. Dahlias produce large, showy inflorescences that are composite heads with numerous ray florets surrounding a central disk. Flower forms range from single to fully double, and cultivated varieties are grouped into classes such as decorative, ball, pompon, cactus, anemone, and peony or dinner plate.

In cultivation, dahlias are grown as garden plants and, in temperate regions, are typically treated as annuals or lifted for winter storage. They require full sun, rich, well-drained soil, and regular moisture. Plants are usually set out after the last frost; depending on the cultivar, heights can range from about 30 cm to 150 cm, with taller varieties requiring staking. Deadheading extends blooming, which generally lasts from mid to late summer into autumn.

Propagation is most commonly by division of tubers, though they can also be grown from seed; however, seed-grown plants can show considerable variation. In climates with frost, tubers should be dug up after the first frost and stored in a cool, dry place over winter.

Dahlias are valued for use in borders and as cut flowers. They hold cultural significance in Mexico, where the dahlia is the national flower, reflecting the region’s native flora and heritage. Common pests include aphids, slugs, and spider mites, while powdery mildew and botrytis can affect plants in humid conditions.