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Cosmos sulphureus 'The Golden Cosmos'

The Mexican Aster

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Cosmos sulphureus 'The Golden Cosmos'

The Mexican Aster
  • Buy 3 for €1.08 each and save 10%
  • Buy 5 for €0.96 each and save 20%

Availability: In stock

Packet Size:2.5gms
Average Seed Count:250 Seeds


When Spanish explorers were looking for riches in Mexico to send back to Spain, one of the treasures they found was the Golden Cosmos flower, Cosmos sulphureus.
In the last decade Cosmos sulphureus has become increasingly popular as more gardeners have come to appreciate its ease of growth, spectacular flowers and attractiveness to bees and butterflies.

Cosmos sulphureus produce huge quantities of bowl-shaped flowers in a range of terrific golden hues that are 5 to 7cm (2 to 3in) in diameter. With rich green lacy foliage, the plants grow to around 120cm (4ft) tall. By late summer they form a beautiful rounded clump.

Like its cousin Cosmos bipinnatus, Cosmos sulphureus is very easy to grow, they are the perfect choice for children or the armchair gardener. Disease free, heat and pest-resistant, Cosmos thrives on neglect and is able to withstand drought and survive harsh conditions in urban gardens and wildflower plantings. Deserving a sunny site in any garden, these adaptable plants are absolutely great for cutting, pots and borders.

Sowing: Sow indoors March to April, or sow outdoors April to May
Sow indoors in early spring 3 to 4 weeks before planting outside, alternatively, the seed can also be sown directly where they are to flower in mid to late spring. Keep soil moderately moist during germination.

Sowing Indoors:
Use well drained soil and cover to a depth of 3mm (1/8in). When large enough to handle, transplant the seedlings into small pots to grow on. Acclimatise to outdoor conditions for 10 to 15 days before planting out after all risk of frost 15cm (6in) apart.

Sowing Direct:
Prepare the ground well and rake to a fine tilth. If sowing more than one annual in the same bed, mark the sowing areas with a ring of sand and label. Sow 1mm (1/18th in) deep in rows 30cm (12in) apart.
Sow seed sparingly or they will choke out other seedlings.
The seedlings will appear in rows approx 6 to 8 weeks after planting and can be easily told from nearby weed seedlings. Thin the seedlings out so they are finally 30cm (12in) apart. Carefully replant thinned plants.

When the seedlings have three pairs of leaves, pinch out the tips, leaving at least one pair of leaves.
Stake the taller varieties with a single or tripod of canes and some twine. Cosmos foliage is finely-cut into threadlike segments. When flowering, the taller varieties may become top heavy. This problem is alleviated when grown in groups, as the bi-pinnate leaves interlock, and the colony supports itself.
Deadhead to prolong flowering and encourage new flower buds.
Cosmos sulphureus is genetically adapted to its desert habitat. In the garden its needs are minimal: a sunny location and average to poor well drained soils with average to dry moisture. Plants need moisture to become established but are drought tolerant as mature specimens. If drought is prolonged the growth and flowering will be stunted so only water the plants in an extended drought.
If planted in overly fertile soil, fertilised on a regular schedule, or in damp conditions, performance is diminished. Too much fertiliser inhibits flowering.
Cosmos sulphureus is a short day plant, which is why it blooms most prolifically after summer solstice in the northern hemisphere when the days start getting shorter and darkness is longer. Expect flowering until hard frosts.
At the season's end, don't be too quick to pull up withering cosmos plants. Birds (particularly gold finches) love to snack on their seedheads in autumn, and the seeds that they miss may drop to the ground and reward you the next year by sprouting into a whole new crop.

Cut Flowers:
Cosmos is a cut-and-come-again bloomer, meaning that the sooner you cut the blooms, the quicker new buds will pop up to replace them. The blooms appear so profusely that you'll still have plenty of colour in the garden after you've picked your flowers.
Cut the blooms in the early morning hours, and select stems with flowers that have petals just beginning to unfold. Remove the leaves below the water line. The bloom will fully open once in the vase and if you sear the stem end in boiling water for twenty seconds they will last a week in water.

Plant Uses:
Bed and Borders, Wildlife, Bee or Butterfly gardens, Cut Flowers.

When Spanish explorers were looking for riches in Mexico to send back to Spain, one of the treasures they found was the golden cosmos flower, Cosmos sulphureus.
In 1789 the flower made its way to England with the wife of the Spanish ambassador to Spain. Half a century lapsed before the golden cosmos reached the US indirectly from England and Spain and directly via Mexico.
Horticulturists are always trying to improve on Mother Nature and today many cultivars of Cosmos sulphureus are available. Depending on variety they will grow anywhere from 30cm to 200cm (1 to 7ft) in height.

Cosmos have been reassuring gardeners ever since the 1930s, when breeders first coaxed cosmos to bloom earlier than the native Mexican species, the flower-growing public has been hooked.
Like many of our warm weather annuals such as marigolds, Cosmos originated in Mexico and South America. Spanish priests grew cosmos in their mission gardens in Mexico. The evenly placed petals led them to christen the flower "Cosmos," derived from the Greek kosmos, the word for harmony or ordered, or balanced universe. From this we also get the common name of "The Mexican Aster".
The species name sulphureus is taken from the Latin meaning 'sulphur coloured’, referring to the yellow blooms of the species. It is commonly called the Sulphur Cosmos or Golden Cosmos.

Additional Information

Additional Information

Packet Size 2.5gms
Average Seed Count 250 Seeds
Family Asteraceae
Genus Cosmea, Cosmos
Species sulphureus
Common Name The Mexican Aster
Hardiness Half Hardy Annual
Hardy Shades of orange.
Flowers May to August
Height To 90 to 120cm (36 to 48in)
Spread 45cm (18in)
Position Needs full sun to flourish
Soil Lean, well drained, sandy soils.
Germination 7 to 10 days at 20-30*C (68-86*F)

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