Fast growing annual, loved for its bright showy flowers that attract many beneficial insects into the garden. Excellent for late summer colour. It is a bushy plant with fine, feathery foliage. Flowering profusely from summer into autumn. A brilliant choice for filling gaps in borders or at the margins. Cosmos will thrive in any bright sunny spot, so long as the soil is well-drained and not over rich.
Family: Asteraceae or Compositae
Botanical Name: Cosmos
Common Names: cosmea, Mexican aster, Spanish needles
Foliage: Deciduous, finely dissected, mid-green fern-like foliage.
Flowers: Large blowsy daisy-like flowers, borne on long stalks. Available in a wide range of colours from deep burgundies and reds to orange, yellow, pink and white. Single and double forms are available.
Flowering Period: Mid-summer to early autumn (July to October).
Soil: Grow in a moderately fertile, moist but well-drained soil. Loam, chalk or sandy soil, any pH.
Conditions: Best in full sun. Grow in a west or south facing aspect, in either an exposed or sheltered possition.
Type: Half-hardy annuals and tuberous perennials.
Origin: Mexico, America and west Indies.
Hardiness: H3 - Hardy in coastal and milder areas of the UK (-5 to 1).
Cosmos is the perfect choice for adding a fresh look to flower beds, borders, pots and containers. Providing a summer-long display.
Needs very little care and attention if growing conditions are right. Cosmos will thrive most light soils, so long as the position is sunny. It will be at its best in a hot dry corner.
Suitable for town and city gardens, courtyard gardens, cottage or informal gardens. Ideal for the middle or back of the border. The fine feathery foliage also makes an good foil for other plants.
Long-lasting as cut flowers.
Compact varieties (below 60cm) will not usually need staking. Use twiggy sticks to provide support for taller varieties or in exposed areas.
Mulch perennial types in autumn in mild areas. In colder areas lift perennial tubers and protect over winter.
Deadhead regularly to extend the flowering period or leave the seed heads to ripen and self-seed if required.
Generally pest free but can be affected by aphids and slugs. May be susceptible to foot rot and grey moulds.
In mild districts annuals can be easily grown from seed, sown directly outdoors in spring (April to May). Choose a well-drained, light garden soil, and a sunny spot.
Alternatively, sow mid-spring under glass at 16°C. Prick out into pots and harden off before planting out in late May. Note: as cosmos seeds are large, they can easily be sown in modules.
Propagate perennials by taking basal cuttings in early spring. Root using bottom heat.
Most garden varieties are bred from C. bipinnatus and the smaller flowered C. sulphureus.
C. bipinnatus has finely dissected foliage and elegant
flowers of white, red or shades of pink. Height to
C. bipinnatus Sonata Series, flowers from June to October in shades of pink, red and white. Height 2ft (60cm).
C. bipinnatus 'Candy Stripe', red-and-white patterned flowers, August to September. Height up to 3ft (90cm), spread 18in (45cm).
C. bipinnatus 'Gazebo Red', early, large flowering variety, in cerise to red flowers. Height to 2.5ft (75cm).
C. bipinnatus 'Gloria', pink central dark bands.
C. bipinnatus ‘Psyche’ , semi-double and single, pink, red or white blooms with frilled petals.
C. bipinnatus ‘Purity’, white flowers.
C. bipinnatus 'Rubenza', ruby red blooms, fading to a mix of shades. Height to 3ft (90cm).
C. bipinnatus 'Seashells' in pink, crimson or white. Height to 3ft (90cm), spread 18in (45cm).
C. bipinnatus 'Sensation Gloria', good for the back of the border. Height to 3ft (90cm), spread 18in (45cm).
C. bipinnatus 'Sensation Mixed' has white, pink or red flowers. Height to 3ft (90cm), spread 18in (45cm).
C. bipinnatus 'Versailles Tetra', large slate-pink flowers. Height to 3ft (90cm), spread 18in (45cm).
C. sulphureus (sulphur cosmos), small to medium size yellow flowers. Height 2-3ft (60-90cm), spread 18in (45cm).
C. sulphureus 'Bright Lights', small, double flowers in yellow, orange, and scarlet. Height to 3ft (90cm), spread 18in (45cm).
C. sulphureus 'Klondyke', best-known cultivar, with double orange, red, and yellow flowers. Height 2ft (60cm).
C. sulphureus 'Sunset Orange', early flowering orange semi-double flowers. Height to 3ft (90cm).
C. sulphureus 'Sunny Gold', orange, double flowers. Dwarf strain, 1ft (30cm).
C. sulphureus 'Sunny Red’ (double vermilion flowers).
C. sulphureus 'Diablo' with semi-double, orange blooms.
C. sulphureus 'Bright Lights’ has small double yellow, orange or scarlet flowers.
C. sulphureus ‘Lemon Twist’ (acids yellow flowers)