Garden Cosmos 'Purity'

Do not apply large doses of fertilizer as flowering will be suppressed.
Deadhead to prolong flowering and encourage new flower buds. Leave a few plants to die down and self seed. Others can be pulled up and composted

Plant in a location that enjoys full sun and remember to water moderately. Keep in mind when planting that Purity is thought of as half hardy, so remember to watch your frost dates and ensure you have this plant protected when the temperature dips. Purity tends to grow best in a soil ph of between 6.6 and 7.8 meaning it does best in weakly acidic soil - weakly alkaline soil.

Sow indoors March-April, or 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. ¹

For indoor sowing, sow seed on the surface of a good free draining, damp seed compost. Cover with a very fine sprinkling of compost or vermiculite. Place in a propagator or seal container inside a polythene bag and palcae at 20-25C until after germination which usually takes 7-14 days. Do not exclude light, as this helps germination.²

Ensure a distance of 0.98 inches (2.5 cm) between seeds when sowing - look to sow at a depth of approximately 0.12 inches (0.3 cm). Soil temperature should be kept higher than 20°C / 68°F to ensure good germination.

By our calculations, you should look at sowing Purity about 28 days before your last frost date.

Transplant seedlings when large enough to handle into trays or 7.5cm pots. Grow on in cooler conditions for 10-15 days before planting out after all risk of frost, 45 cm apart. ²

Ensure that temperatures are mild and all chance of frost has passed before planting out, as Purity is a half hardy plant.

Cosmos, like many of our warm weather annuals such as marigolds, 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,” the Greek word for harmony or ordered universe. From this we also get the common name of “The Mexican Aster”.¹

The botanical epithet is from the Latin bipinnatus meaning “staunch” or “like two small wings”.³

The mexican aster, Cosmos bipinnatus ‘purity’

¹ Seedaholic.com details on Cosmos Purity

² Description from Thompson & Morgan seed packet.

¹ Latin Dictionary