Cosmos are great flowers for your garden - they attract pollinators, are colorful, and come back year after year. Pick a spot in your garden in full sun or partial shade (more sun means more flowers). Cosmos can grow between 18-72”, depending on variety, plant tall varieties where they won’t shade lower growing plants.
If your area still has cold weather, start your cosmos seeds indoors 4-6 weeks before your last frost date. Cosmos seeds germinate in 5-14 days and should be transplanted when they are 3-4” tall. Cosmos can be grown in pots, just make sure that they are well draining.
If starting cosmos seeds outdoors, wait until all danger of frost has passed and your soil has warmed to about 60oF. Cosmos like soil that is not too rich, as overly fertile soil will encourage foliage instead of blooms. Seeds can be broadcasted or planted 12-18” apart, 1/2” deep. Water seeds in well, and add compost/mulch, but fertilizer is unnecessary.
Cosmos love summer heat and will bloom until the first frost. As the blooms die, more seeds will be dropped into your soil or carried away by wind, so don’t be surprised if you see cosmos popping up in other places or for years to come! You can also collect the seeds to replant if there is an especially hard winter and previously fallen seeds don’t germinate.