Cosmos bipinnatus 'Sea Shells'
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Family: Asteraceae
Pronounced: KOS-mos bi-pin-AH-tus
GROWING GUIDE
Geographic Origin:
Garden.
Plant Group:
Annual.
Hardiness:
Sunset zones: All zones.
USDA zones: 7-11.
Mature size:
Height: 36 inches (90 cm).
Width: 18 inches (45 cm).
Flowering period:
Two and a half months after sowing seed, flowers begin to blossom.
Flowering attributes:
Each floret is rolled into tubes in white, pink and burgundy colors.
Leaf attributes:
Pinnaticsect green leaves up to 12 inches long give this annual a lacy fern effect.
Light:
Full sun.
Soil:
Moist, humus-rich, well-drained soil is ideal, although cosmos can also grow on poor, lean soils.
Feeding:
Add a complete organic fertilizer when planting.
Propagation Methods:
Sow seed at 61-64°F (16-18°C) and transplant out after all danger of frost. | Sow in situ in late spring.
Pruning Methods:
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 in Mexico where Spanish priests grew them in their mission gardens. They named the species Cosmos because of the evenly spaced petals. Kosmos is the Greek word for harmony or ordered universe. Hybrids such as C. 'Sea Shells' have been bred from the species with a unique roll to its florets.
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.
Debra Teachout-Teashon
Photographed in author's garden.
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