Bryan McAllister’s personal reference notebook
July 30, 2026Short & citedBlog
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Field Notes • Botany

Dahlia

Dahlia is a genus of tuberous, herbaceous flowering plants in the aster family (Asteraceae), native to Mexico, Central America, and parts of northern South America.

Updated July 30, 20261 min readCited sources

Dahlias are a colourful genus of tuberous plants native to the Americas, but in most of Canada they are treated as tender perennials that need special care over winter.

What it is

Dahlias are flowering plants in the aster family (Asteraceae), native to Mexico, Central America, and northern South America. They grow from tubers, not true bulbs, and are known for their showy, diverse blooms. Gardeners value them for their wide range of flower forms, sizes, and colours.

Cultivation tips

Plant tubers in full sun after the last frost, once soil has warmed. Water deeply, stake taller varieties, and limit nitrogen later in the season. In Canada, dahlias are often lifted in autumn after frost, dried, and stored indoors in a cool, dark place until spring.

Varieties and uses

Dahlias are classified by bloom form: single, anemone, cactus, decorative, ball, pompon, and dinnerplate. This diversity makes them popular as cut flowers and ornamental garden plants. The genus honours Swedish botanist Anders Dahl.

In short

  • Dahlias are tuberous perennials, native to the Americas.
  • They need full sun, well-drained soil, and regular watering.
  • In Canada, tubers are typically dug up and stored over winter.
  • Their flower forms range from single to dinnerplate sizes.
Canadian angle

In most of Canada, dahlias are treated as frost-tender perennials: gardeners usually plant them after spring frost and lift tubers in autumn for indoor storage over winter.

Quick questions

How do you grow dahlias?
Plant tubers in full sun after frost danger, in warm, well-drained soil. Water deeply, stake tall varieties, and avoid excess nitrogen later in the season.
When should you plant dahlias?
Plant after the last frost, once the soil has warmed. A common guide is to plant them around the same time as tomatoes.
How do you store dahlia tubers?
After frost, lift tubers, let them dry, and store in a cool, dark, dry, frost-free place. Many gardeners use peat moss, vermiculite, or paper bags.

Sources

  1. American Dahlia Society — https://www.dahlia.org/growing/fundamentals-of-growing-dahlias/
    Supports: Planting after soil warms and frost risk passes; staking and fertilization guidance.
  2. The Home Depot — https://www.homedepot.com/c/ah/how-to-grow-dahlias/9ba683603be9fa5395fab901f3c72f24
    Supports: Dahlias are native to the Americas, belong to Asteraceae, grow from tubers, and are dug up in colder zones.
  3. Three Acre Farm — https://www.threeacrefarm.net/blog/2018/4/4/beginners-guide-to-growing-dahlias
    Supports: Tubers are storage organs; winter storage in a cool, dark, dry location.
  4. Joe Gardener — https://www.joegardener.com/podcast/dahlia-growing-breeding-kristine-albrecht/
    Supports: Full sun, planting after last frost, soil temperature around 50°F, storage temperature around 43°F.
  5. Country Living — https://www.countryliving.com/gardening/garden-ideas/a35696558/dahlia-care/
    Supports: Zones where tubers can overwinter, digging after frost, and flower-cutting guidance.
  6. Longfield Gardens — https://www.longfield-gardens.com/blogs/spring-planted-bulbs-how-to/8-tips-for-growing-better-dahlias
    Supports: Dahlia buds form at the stem base above tubers; tubers store food rather than produce sprouts.