Seed To Bloom:
Start in pots 4-5 weeks before last spring frost. Keep at about 60-75°F.
Direct sow in spring, after last frost.
WHEN TO SET OUTSIDE
In springtime, after all danger of frost has passed.
PLACEMENT & CULTIVATION
Thank goodness we live in the age of the quick-blooming cosmos. Early 20th-century gardeners had to be content with a fleeting flower or two before the frost came to claim them all. Cosmos today are super floriferous midsummer to fall with reliable bloom in hot and dry weather. Pinch out stem tips when plants are 1' tall to help grow bushy, branching plants with loads of flowers. Start indoors in pots for earlier bloom and sow directly for flowering starting mid-summer. Deadhead regularly and stake early in windy areas, as the branches are quite brittle and can snap off at the central stem. Cosmos attracts numerous beneficial insects, making them a valuable addition to the borders of vegetable gardens too!
Drought tolerant. Water regularly while establishing, then water only during dry, hot spells.
Prefers acidic to neutral
Cosmos thrive in regular soil and may sprawl in nitrogen rich soils. If desired, an application of organic flower fertilizer can be mixed in around plants.
Diseases & Pests:
No major pests or diseases. Powdery mildew can be discouraged with a regular preventative application of a baking soda based spray.
When to Cut for Bouquets:
Harvest when flowers start to open to 1/2 open; best vase life before the flowers are pollinated.