Dahlia
Dahlia hybrids (ASTERACEAE, formerly COMPOSITAE)
Planting and Growing Dahlia
You’ll find everything you need to know to plant and grow dahlia in the accompanying table’s tabs:
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- Flowers, foliage, and root structure of dahlia
- Season of bloom and planting time for dahlia
- Plant hardiness and growing conditions for dahlia
- When, how deep, and where to plant dahlia
- How to plant dahlia
- Watering, fertilizing, care and pests or diseases of dahlia
- Landscape and indoor uses of dahlia
- Comments about dahlia and its features
Growing Dahlia
Summer tuberous root. Deciduous. Stands to 15 ft. (4.5 m) tall. Swirl of 2 or 3 simple, medium-toothed, short to midlength, deep green leaves.
Dahlia Planting and Care Guide
Flowers
Summer–autumn. Bronze, orange, pink, purple, red, white, yellow, bi- or multicolored. Multiple flowers, to 1 ft. (30 cm) wide, with single or layered petals, in widely varied forms from simple or pompon to cactuslike.
Best Climates
U.S.D.A. Plant Hardiness Zones 4–11; ground hardy, zones 9–11.
Soil Type and Fertility
Moist, well-drained soil. Fertility: Rich. 6.5–7.0 pH.
Where and How to Plant
Autumn in full sun, zones 9–11; spring, zones 4–8. Wait until soil temperatures rise to over 60°F for spring plantings as too-cold soils may cause dahlia to fail.
Space 2–3 ft. (60–90 cm) apart, 6 in. (15 cm) deep. Space dwarf hybrids 10–12 in. (25–30 cm) apart, 4–5 in. (10–13 cm) deep.
Proper Care
Moderate. Keep moist summer–autumn; allow soil surface to dry between waterings. Fertilize at planting, then monthly until buds form. Mulch. Pinch foliage buds when 1 ft. (30 cm) tall to promote fullness. Lift, zones 4–7. Protect from frost, wind. Stake to support. Propagate by division in spring.
Lifting and Storing
Dark, 50–60°F (10–16°C), in net bag or open basket of dry peat moss.
About This Species
Good choice for accents, beds, borders, in cottage gardens and landscapes. Good for cutting. Deer, rodent and slug, snail susceptible.
American Dahlia Society Dahlia Categories:
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- Single Dahlia
- Anemone Dahlia
- Colarette Dahlia
- Peony Dahlia
- Formal Decorative Dahlia
- Informal Decorative Dahlia
- Orchid-Flowering Dahlia
- Ball Dahlia
- Pompon Dahlia
- Incurved Cactus Dahlia
- Straight Cactus Dahlia
- Semi-Cactus Dahlia
- Miscellaneous Dahlia
- Fimbriated Dahlia
- Waterlily or Nymphaea-Flowered Dahlia
About Dahlias
Dahlias are long-lasting, summer-blooming flowers that frequently extend their showy bloom into autumn.
More than 20,000 distinctive cultivars comprise the offspring of roughly 27 wild species of the Dahlia genus. All are native to Mexico, Central America and northern South America.
Because there are many hybrids, you’ll find dahlias in a wide range of colors, forms, and sizes. Flowers range in size from 2–12 in. (50–305 mm) wide and are found in every color except blue. There are bedding dahlias as short as 16 in. (40 cm) and dahlia bushes as tall as 8 ft. (2.4 m).
All dahlias are summer bloomers, have tuberous roots, and are tender to frost. In U.S.D.A. Plant Hardiness Zones 4–8, plant dahlias as annuals or lift them after their bloom finishes and store them for spring replanting.
Dahlias were mainstays of heritage gardens at the turn of the 20th century. Their popularity has surged recently as many gardeners rediscovered them. The most popular cultivars stem from hybrids of Dahlia coccinea and Dahlia pinnata (formerly Dahlia rosea).
Classification of dahlias is an active sport, and the current listing of official categories may be obtained from the American Dahlia Society. Dahlias are usually divided for award purposes into the 15 commonly recognized groups found above.
Planting and Caring for Dahlias
Plant dahlias as annuals in U.S.D.A. Plant Hardiness Zones 4–8, or lift them after bloom and store them for spring replanting.
In U.S.D.A. Plant Hardiness Zones 9–11, plant dahlias in autumn and allow their tuberous roots to remain in the garden through the winter. Apply mulch to protect them from occasional frosts.
In other regions, lift them after their blooms fade in autumn, divide and store them through the winter in a net bag or open basket of dry peat moss, and replant them in spring.
Plant dahlias in rich humus, 4–6 in. (10–15 cm) deep, depending on cultivar, spacing them to allow good air circulation and staking tall cultivars to support them.
The best time to plant dahlias is in spring, as soon as soil temperatures have warmed, and after several weeks with minimum nighttime air temperatures above 60°F (16°C).
Divide dahlias in spring only when plantings become overcrowded.
Choose dahlia cultivars according to your planned use. Small varieties, to 2 ft. (60 cm) tall, are best used as bedding plants, borders, and edgings.
Massed plantings of taller forms, to 8 ft. (2.4 m) tall, make an eye-catching landscape feature suitable for island beds, fenced gardens, or raised beds separated by winding paths.
Tree dahlia, Dahlia imperialis, is a perennial, multistemmed, treelike form. It grows 10–20 ft. (3–6 m) tall, making it well-suited for planting as an accent or a background in landscape borders that showcase its attractive blossoms.