How to grow Great Cosmos

Rich, fertile soils tend to produce unusually tall, lanky plants. Cosmos requires full sun.

Direct sow seed in early spring since seedlings are not winter hardy. The average planting success with this species is 80 percent. The plant height is 2 – 4 feet depending on culture and variety selected. Plants will germinate in 7 – 21 days when the soil temperature is optimum for germination at 70 – 80 degrees F. Plant seed 1/16 inch deep by raking into the soil. Plants bloom from May – November. Plants should be sheared every 30 days or whenever seed pods predominate. Plants bloom approximately 50 – 55 days after germination. Cosmos needs to be replanted each spring for continued success.

Cosmos is easy to start from seed. Rich, fertile conditions are not necessary to grow cosmos, but adequate drainage is. The seeds may be sown outdoors after all danger of frost is past and the soil has warmed to at least 65 degrees F. Scatter the seeds and rake into a loose soil — if the seed is planted too deep, germination can be affected. Keep the soil moist for 5 – 10 days after seeding. Seeds will germinate in 7 – 21 days. If the soil temperature is below 65 F., seeds may not germinate as rapidly. Thinning is really not necessary.

Cosmos needs only basic care to provide a colorful abundance of blooms all summer long. After the seedlings emerge, water VERY SPARINGLY. In lieu of any rainfall during an entire month, give the planting bed a long, slow drink. Cosmos is drought tolerant, providing abundant blooms with less water than most other annuals. Herein lies the “problem” which many people encounter when growing cosmos — they “over-care” for their cosmos plants with too much water, too much fertility and too much shade. When “over-care” occurs, cosmos becomes tall and spindly (even when the new, lower-growing varieties are used), and blooms sparsely. The best growers of cosmos practice “tough-love” plant culture. “Tough-love” watering means only watering when the cosmos foliage begins to wilt. “Tough-love” fertility means very little if any soil fertility. “Tough-love” location means no shade and in direct, all-day blazing sunlight.

Cosmos grows best in the worst conditions — hot and dry. This is why cosmos is the best possible annual for New Mexico, Arizona, parts of Utah, Texas and the eastern plains of Colorado etc. When not exposed to “tough-love” growing conditions, this otherwise beautiful flowering plant becomes tall, spindly and sparsely flowered. If you can discipline yourself to do some “tough-love” growing of Cosmos you can produce the lovely pastels which these flowers are known for.

Because cosmos is so easy to grow in the worse conditions spring and summer have to offer, it can be seeded in the spring for early summer bloom or in mid-summer (June) for late summer (August) until frost, bloom as well. Since cosmos seed actually sprout faster in hot soils and the plant grows best in hot, dry summer temperatures, you can increase your plant population and bloom display by cutting back spring-planted cosmos. When the spring-planted cosmos begins to look as if there are an abundance of dried seed pods, do not remove the plants — encourage re-bloom simply by cutting the plants back to 12 – 18 inches high. They will be back in bloom in a month and the seed cut off will fall to the ground, germinate in the hot soil and increase the density of your plant population and the eventual bloom display.
Cosmos is generally a pest-free annual.
Cosmos is the best annual for hot, dry locations
Cosmos is the best annual for poor soils
Cosmos is a self-seeding annual
Cosmos is an annual which can be direct – seeded into the planting area
Cosmos flowers can be used as cut flowers.

Fresh cut cosmos blooms make a bright airy bouquet. An arrangement of cosmos can last for 7 – 10 days. Select flowers whose petals have just unfolded; they will open fully once cut. Cut the flowers in the morning when their water content is highest and immediately place them in a deep container of tepid water. Before arranging, strip foliage from the lower portion of the stems. If leaves are submerged under water, they will decay quickly, shortening the life of the bouquet.

Cosmos flowers are suitable for drying. There are many summer flowering annuals which are excellent for drying. Marigold, salvia, cosmos, zinnia, coreopsis and Gloriosa daisy are among the most popular and make fine dried specimens.
Cosmos are suitable for backgrounds and screens
Mid-sized varieties add an airy note when inter-planted with evergreen shrubs. Edge a garden path or driveway with medium height cosmos in pastel or bright hues. Because they bloom so freely all summer and into early fall, cosmos is recommended for these highly visible areas.
Cosmos attracts birds, bees and butterflies.




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