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Dahlia
Dahlia
dahlia

- Height 10-60 in (25-150 cm)
- Planting distance 1-4 ft (30-120 cm)
- Flowers midsummer to first severe frost
- Any well-drained garden soil
- Sunny or lightly shaded site
- Tubers available midwinter to late spring
- Hardy to zone 9; farther north lift and overwinter tubers indoors

Dahlias come in a range of forms, sizes, and colors unmatched by any other garden plant. Their glorious flower heads appear from midsummer until midfall or the first severe frosts, filling the garden with color when most other plants are past their best. Garden dahlias are grown from tubers or cuttings, but dwarf bedding dahlias are grown from seed and are treated as true annuals. The bold flower heads and strong colors of dahlias make them outstanding plants for garden decoration and cutting. Depending on their size, they can be grown in beds of their own, in perennial borders, in open shrubberies, or along walls. They prefer a sunny site but will tolerate shade. As they are only half-hardy, the tubers should be lifted in fall north of zone 9 stored in a frost-free place over winter. They are easy to grow if you just want bright splashes of color in late summer and fall. If you're aiming for the perfect exhibition flower head, however, there's a host of refining techniques that specialist growers use.

Popular species and cultivars
Border dahlias are divided into nine groups, determined by the shape of the flower heads.
Anemone-flowered dahlias have blooms up to 4 in (10 cm) wide that resemble anemones: their double flowers have flat outer florets that surround a dense group of shorter tubular florets, often of a different color. The plants reach 10-18 in ( 25-45 cm) high and should be grown 1-11/2 ft (30-45 cm) apart in beds, borders, tubs, or deep window boxes. This is one of the rarer groups; it includes several cultivars in pastel shades. Cultivars available are 'Comet' (maroon), 'Honey' (apricot-pink), and 'Sweden' (yellow).
Cactus dahlias have fully double blooms with pointed ray florets. This group is divided into sections, determined by the size of the blooms. Giant cultivars reach 4-5 ft (120-150 cm) high with blooms over 10 in (25 cm) wide; plant 4 ft (120 cm) apart. Their flowers don't appear until early fall. Large cultivars are also 4-5 ft (120-150 cm) high with slightly smaller blooms at 8-10 in (20-25 cm ) wide; plant 4 ft (120 cm) apart. Medium cultivars 31/2-41/2 ft (105-135 cm) high with blooms 6-8 in (15-20 cm) wide; plant 3 ft (90 cm) apart. Small cultivars are 31/2-4 ft (105-120 cm) high with blooms 4-6 in (10-15 cm) wide; plant 21/2 ft (75 cm) apart. Dwarf cultivars are 3-4 ft (90-120 cm) high with blooms up to 4 in (10 cm) wide; plant 21/2 ft (75 cm) apart. All cactus cultivars are easy to grow and make impressive cut flowers. Popular cultivars are 'Apple Blossom' (rose with lighter center), 'Doris Day' (bright red), and 'Orchid Lace' (white with purple tips).
Collarette dahlias have blooms 4 in (10 cm) wide, each single-flowered with an inner ring or collar (often of another color) and a central disk. This group includes cultivars reaching 30-40 in (75-100 cm) high. Set the plants 2-21/2 ft (60-75 cm) apart. Collarette dahlias have especially strong stems, which make them favorites among flower arrangers. Popular cultivars are 'Awaikoe' (mahogany-red with white collar), 'Jack O'Lantern' (orange with yellow), and 'Kaiserwalzer' (fiery red and yellow).
Decorative dahlias have double blooms consisting of broad, flat rat florets without central disks. This large group is subdivided into sections according to flower form and size. Formal decorative cultivars are fully double with all the florets regularly arranged with slightly incurved edges and flattened tips. Informal decorative dahlias are also fully double but with looser, less regular inflorescences the petallike rays are not regularly arranged. Decorative dahlias may be giant, large, medium, small, or even miniature, and can range in height from 3-5 ft (90-150 cm), depending on the type. Blooms may be spectacular - 10 in (25 cm) wide or more. Space tubers according to the expected stature of the cultivar: giants should be planted 4 ft (120 cm) apart, miniatures just 21/2 ft (75 cm). Decorative dahlias have an extensive color range and are good for both exhibiting and cutting. Popular cultivars are 'Daniel Edward' (formal, fuchsia-purple), 'Duet' (formal red and white), 'Edinburgh' (formal, maroon and white), 'Envy' (informal, red), 'Heidiland' (formal, fuchsia), 'Playboy' (informal, yellow), and 'Purple Taiheijo' (informal purple).
Peony-flowered dahlias have blooms up to 5 in (13 cm) wide, each consisting of two or more rings of flat ray florets and a central disk. The plants reach 40 in (100 cm) high and should be grown 2-21/2 ft (60-75 cm) apart. Only a few cultivars are available. they include 'Bishop of Llandaff' (scarlet), 'Gerrie Hoek' (pink), and 'Japanese Bishop' (dark orange with blackish foliage).
Pompon dahlias have fully double globular-shaped flowers, 2 in (5 cm) wide. the free-flowering plants reach 3-4 ft (90-120 cm) high and should be planted 2 ft (60 cm) apart. Their selling point is their long-lasting cut flowers. Popular cultivars include 'Andrew Lockwoode' (lilac), 'Moorplace' (purple), and 'Stoneleigh Cherry' (red).
Semicactus dahlias have flowers similar to the cactus cultivars, but the ray florets are wider. They are divided into the same sections as the cactus group, determined by flower size. Semicactus dahlias are excellent for exhibiting. Popular cultivars are 'Andriana' (white) and 'Reginald Keene' (orange and flame).
Show or Ball dahlias have blooms similar to those of pompon dahlias, but these flowers are larger and more ball-shaped and are sometimes flattened on top. Reaching 3-4 ft (90-120 cm) high, they are suitable for growing in mixed borders, cutting, and exhibiting. Plant the tuber 21/2 ft (75 cm) apart. The cultivars are subdivided into two groups: small ball with blooms 4-6 in (10-15 cm) wide and miniature ball with blooms up to 4 in (40 cm) wide.
Single-flowered dahlias have blooms up to 4 in (10 cm) wide, each with a single outer ring of florets and a central disk. The plants are 12-20 in (30-50 cm) tall and should be grown 1-11/2 ft (30-45 cm) apart. Cultivars in this group can be grown in beds or mixed borders, as they don't require support. Their flowers are abundant and will last a long time if deadheaded regularly. Popular cultivars include 'G. F. Hemerick' (soft orange), 'Irene van der Zwet' (soft yellow), 'Nellie Geerlings' (red), and 'Sneezy' (white).

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