To provide drainage the cosmos were planted on a slight slope on my side yard. The soil in this area is rich with organic matter. Normally I take care in the way I plant but I was in a hurry so I literally tossed the seeds into a new bed and then planted them where the seeds landed by covering the seeds with a half inch of potting soil and a light layer of mulch.
I cared for the seeds by watering them so that the ground was evenly most but not wet.
We had an unusual spring as the days were cool well into May and there was flash flooding. I was certain that the seeds were washed away. However 21 days later I viewed new growth. Cosmo seedlings were pushing upward through the soil.
Fertilize your cosmos monthly throughout the growing season. I use miracle grow mixed with water. The hose end fertilizer is a good choice.
The cosmo will bloom throughout fall as long as there is sun and no freeze.
Learn more about cosmos by viewing this YouTube video