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Gardening in the Rainy Zone.
Cosmos bipinnatus 'Psyche Mix'
Pronounced: KOS-mos bi-pin-AH-tus
Sunset zones: All zones.
USDA zones: 7-11.
Height: 4 ½ feet (1.37 m).
Width: 18 inches (45 cm).
Two and a half months after sowing seed, flowers begin to blossom.
Double frilly petals, on 4-inch flowers in white, pink and burgundy colors.
Pinnaticsect green leaves up to 12 inches long give this annual a lacy, fern effect.
Moist, humus-rich, well-drained soil is ideal, although cosmos can also grow on poor, lean soils.
Add a complete organic fertilizer when planting.
Sow seed at 61-64°F (16-18°C) and transplant out after all danger of frost.
Sow in situ in late spring.
Deadhead flowers to prolong blooming.
Rainy Side Notes
Cosmos usually find their way into my garden. They are excellent plants for the wildlife garden, providing nectar for bees and butterflies and seeds for the birds. Late in the growing season, I watch in amazement when flocks of goldfinches and other small birds descend upon the cosmos and make a feast from the seeds. Be sure you leave enough seed heads toward the end of the season for the birds. Alternatively, you can plant some for the birds and allow them to set seed early, while you keep cutting flowers from other plants.
A New World plant, C. bipinnatus originates from Mexico, and many fine hybrids such as 'Psyche Mix' have been bred from the species. This is one of the largest and showiest flowers of all the cosmos. As a cut flower, it has a long vase life. Even the leaves serve well as greenery for the bouquet. Easy to grow and providing many benefits for the gardener as well as providing benefits for wildlife, this should find a way into your garden as well.
To encourage long stems, pinch plants early, near the base of plants, or wait until the plants are 18 inches tall and shear them back to 12 inches. This encourages better branching and makes harvesting the flowers easier.
Harvest after the first petals are opening up, but are not totally opened. Vase life in water is 4-6 days. When harvesting for drying the flowers, all the outer petals should be opened. Dry in silica gel for 2-3 days or borax for 4-6 days.
Cosmos are drought tolerant and thrive on neglect; do not pamper these plants.
Photographed in author's garden.