A stalwart of the late summer border, Dahlias come in a wide range of flower styles, shapes, sizes and colours. Border forms are generally larger named varieties, grown from tubers. Bedding forms are usually smaller and easily grown from seed.
Family: Asteraceae (daisy family)
Botanical Name: Dahlia
Other: named after the 18th-century botanist Anders Dahl
Foliage: deciduous, pinnately divided, green leaves.
Flowers: large showy flower heads, singe or double.
Flowering Period: Mid-summer to early autumn (first frosts).
Soil: any moist but well-drained, fertile soil. Chalk, clay, loam or sandy. Any pH.
Conditions: Best grown in full sun, in a south or west facing aspect and a sheltered location.
Habit: bushy, upright.
Type: Tuberous-rooted tender perennials.
Origin: subtropical Mexico
Hardiness: H3 - hardy only in mild areas of the UK.
Easy to grow. Dahlias tollerate a wide range of soil types and will grow best in full sun. Tubers can be potted-up and brought on early in a cool greenhouse. Plant them outside from May to early June, in a fertile, humus-rich well-drained soil.
If you are planning ahead for next year, dig in some well-rotted manure in the autumn to improve the soil structure.
Dahlias can be grown in flower beds, borders, pots and containers and are suitable for virtually any garden type, apart from dry gardens.
Good as cut flowers. Pick flowers regularly to encourage more flower buds to form.
Dahlias are not difficult plants to care for. Water regularly during dry weather and water container grown plants daily. Once flowers buds appear, feed with a high potash feed every few weeks until the end September. Pinch out growing tips if you want to encourage a more bushy habit. Stake taller plants and those with large heavy blooms, which may otherwise droop.
Once foliage has died back in the autumn, cut back stems to ground level. Unless you have very mild winters, lift and clean the tubers and store in a cool dry place, ready for next spring.
Deadhead regularly to extend the flowering period.
Susceptible to wide range of problems, including aphids, capsid bug, earwigs and caterpillars.
Propagate by taking basal shoot cuttings from sprouted tubers in the spring. Alternatively, divide the tubers, ensuring that each division has a viable bud.
Bedding dahlias can easily be grown from seed, sown undercover in the spring (usually late March). Once seedlings are mature, prick out into individual pots, harden off and plant-out once all danger of frost has passed.
Dahlias are sub-classified into groups, according to their flower shape and size:
Bedding Dahlias are small and easily grown from seed. Most seed suppliers provide a range of mixed colours, including:
'Bishop's Children' striking mixed
collection. Height to 29" (75cm).
'Double Extreme' attractive dwarf selection, producing a mass of high quality double and semi double flowers in an rich colour mixture. Height to 18-24 in (45-60cm).
coccinea 'Species Mixed' free flowering mixture of delicate single flowers in several colours, many in bicolour shades. Height to 60in (150cm).
'Coltness Hybrids' mixed colours. Height to 18in (45cm). Available from Chiltern Seeds.
'Figaro Mixed' classic dwarf mixture of double and semi-double blooms. Height to 12" (30cm).
'Rigoletto' colourful and compact in mixed colours. Height to 12" (30cm).
'Sunny Reggae' mixed shades of reds, apricots and oranges. Height to 20" (50cm).
'Unwins Dwarf Hybrids' classic mixed semi-double blooms. Available from Unwins Seeds.
These have a formal shape and are fully double with no central disc. They have broad and flat florets, blunted at the tips, and often slightly twisted. An ideal form for cut flower displays.
Popular cultivars include:
'Arabian Night' rich red flowers. Height to 4ft (120cm)
'Garden Wonder' large-flowered red. Height 3 to 3.5ft (90 to 110cm)
'Kelvin Floodlight' large primrose yellow blooms. Height to 2.5 ft (80cm).
'Thomas Edison' purple to magenta pink. Height to 3ft (100cm).
'Edinburgh' small decorative with
pinkish purple bicolour flowers blending through to
white at the tips. Height to 4ft (1.2m).
'Pink Katisha' strong bold pink flowers. Height to 3.5ft (110cm).
Fully double flowers with narrow, pointed florets, often rolled back or quilled. Popular cultivars include:
'White Star' white flowers. Height
to 3.5ft (110cm).
'Apple Blossom' pink flowers with a paler centre.
‘Doris Day’ small red flowers. Height to 3.5ft (110cm).
‘Yellow Galator’ yellow flowers. Height to 4ft (120cm).
These are similar to the cactus type but the florets are broader and quilled for up to half their length. Popular cultivars include:
'My Love' pure white flower with
greenish yellow centre. Height to 4ft (125cm).
'Park Record' apricot-orange flowers lemon tinted centre. Height to 3ft (90cm).
‘Frigoulet’ bi-coloured red and white spiky petals. Height to 4.5ft (140cm).
‘Pink Preference’ small yellowy pink blooms. Height to 3.5ft (110cm).
Fully rounded blooms, sometimes flattened on top. The florets are arranged spirally, with blunt or rounded tips. Each floret is rolled for more than half its length. Popular cultivars include:'Sylvia' warm orange ball shaped flower with the curvaceous petals. Height to 3ft (90cm).
Similar to ball types, however, the blooms are much more globular in shape. The florets are rolled for the whole of their length. Popular cultivars include:'Viking' with deep red ball shaped flowers. Height to 3ft (90cm).
These have flowers
made up of stamens, with a single
row of florets round the edge. An
inner collar of smaller florets surrounds
the stamens, sited between
these and the petals. Popular cultivars include:
'Alsterguss' red blooms with a yellow centre. Height 2 to 4ft (60 to 120cm)
'Danum Torch', pale yellow red
flushed flowers with pale yellow inner ray florets
and gold centres. Height
4 to 8 ft (150 to 250cm).
'CanCan' pink with yellow inner ring. Height 2 to 4ft (60 to 120cm)
'King of Hearts' pink with yellow centre. Height 2 to 4ft (60 to 120cm)
'Ruwenzori' scarlet and yellow. Height 2 to 4ft (60 to 120cm)
Have a central stamen disc, with a single outer ring of large flat florets, which may overlap. Popular cultivars include:
'After Eight' single, near-white
flowers over deep purple foliage. Height to 2.3ft (70cm).
'Knock Out' single to semi double bright yellow flowers with orange centres. Dark purple-black leaves. Height to 2.5ft (80cm).
'Happy Single Collection' low growing, strong flower colours, often two tone, over rich dark foliage. Height to 2ft (60cm).
'Orangeade' a blend of orange and red flowers. Height to 12-18in (30-45cm).
Also known as powder puff Dahlias, they have a
cushion of double tubular petals, surrounded by a ring
of swept back larger petals. Popular cultivars include:
'Comet' dark red maroon flowers. Height to 4ft (125cm).
'Floorinoor' orange petals, surrounded by a collar of pink petals, each with a yellow base. Height to 4ft (125cm).
These are double opened centred flowers with two or more rows of large petals surrounding a central disc.
One of the most popular Peony-flowered Dahlias is 'Bishop of Llandaff'.