Cosmos bipinnatus or the Mexican aster is a fine half-hardy annual to grow in any garden. The tall frothy stems produce many single dahlia like flowers in bright colours ranging from white to carmine

Description of Cosmos

• The single flowers have 8 petals that open wide to reveal a ray or center disc of florets and yellow stamen.
• Cosmos flowers from July until October.
• Plants vary in height from 24-48in dependent on variety.
• Excellent for cutting and make very attractive pot plants for summer flowering in a cold greenhouse.
• Cosmos has single dahlia-like blooms that are 3in or more across.
• The leaves are simple, pinnate, or bipinnate, and arranged in opposite pairs.
• The plants have a light airy see through structure

Cultivation Tips for Cosmos

• Easy to grow from seed or buy as ready grown plants.
• Most Cosmos will self seed if left to set and distribute seed.
• Sow 3mm (1/8in) deep in spring at 21 -24C (70-75F) in a good seed compost. Keep soil damp but not wet, sealing in a polythene bag after sowing is helpful.
• Germination usually takes 5-10 days. When seedlings are large enough to handle, transplant and grow on in cooler conditions.
• Gradually acclimatise to outdoor conditions for 10-15 days before planting out after all risk of frost, 60cm (24in) apart in a sunny spot on light well drained soil.
• Cosmos like well-drained but light yet moist soil.
• Can be grown as pot plants in cool well ventilated areas with plenty of light.

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Special Growing Tips for Cosmos

• Can get blown about because of their height and delicate foliage so might need staking, depending on position.
• They will attract Goldfinches and butterflies into your garden
• Cosmos flower again and again after dead heading and some new varieties drop the old flowers to save you this trouble.
• When flowering, the plant can become top heavy. Grow Cosmos in groups so that the bi-pinnate leaves interlock and supports one another.

Varieties, Species and Types of Cosmos

• Cosmos sulphureus ‘Brightness Mixed’ One of the most free-flowering yellow and orange Cosmos of this type. Dwarf and bushy plants upto 2 feet high
• Cosmos bipinnatus Sensationor with purple pink and white flowers.
• Cosmos bipinnatus ‘Double Click Snow Puff’ has spectacular double, white, pom-pom flowers with a delicate hint of blushed pink of
• The Sonata Series, AGM, is an award- winning strain, producing compact plants with large red, rose, pink and white flowers, available as a mixture or in single colours.
• Cosmos atrosanguineus aka Bidens atrosanguinea is the in demand Chocolate Cosmos. These plants are virtually perennial and not very hardy so need protection.

Horticulture Sources and Advice

• You can often obtain seeds or plants from our mail order company of choice Thompson & Morgan
• Cosmos are originally from Mexico and flourishing in warm sun and poor soils.
• Also read Growing Cosmos easy annulas

From Gardeners Tips 2009 Easy to Grow Cosmos:

A bright cheery annual the Cosmos is an easy flower to grow and adds height and interest to a mixed border or looks stunning on its own. The clouds of feathery foliage set off the tall 3-4 feet tall flowers.

Tips for Growing Cosmos

• After all the frost has gone sow Cosmos seeds thinly, direct into the ground and just cover lightly. They like well drained soil and a bit of sun for the best flowering.
• When Cosmos get to about 3 inches tall thin out to 10 inches apart, about enough distance to provide support for one another .
• Pinch out the growing tip when they get to 12-15 inches tall to encourage branching and more flowers.
• They are good as cut flowers, attract wildlife and if deadheaded should flower until the first frost.
• Plant in blocks rather than rows and if exposed to windy conditions provide some support.

Special Cosmos to Grow

• Colours range from white, pink, rose through to hot orange. Cosmos Sulphureus are mainly yellow and ‘Sunny Bars’ is a double yellow.
• The Chocolate Cosmos called Cosmos atrosanguineum is perennial and is best grown from a bought plant. The deep burgundy flowers smell of chocolate.
• Common species are available in mixtures like ‘Sensation’ or the dwarf ‘Sonata’.
• Variety ‘Sea Shells’ has unusual tubular petalled blossom.