Prepare a planting bed in full sun by turning 6 inches of compost into the top 12 inches of soil with a turning fork or tiller. Rake the bed smooth.
Scatter the Candy Stripe cosmos seeds onto the ground and rake them in with a garden rake. Water the bed well.
Water the seeds lightly each day until they sprout, then water sparingly. Cosmos do not like much water.
Fertilize your Candy Stripe cosmos once with a low-nitrogen all-purpose fertilizer when the plants reach 6 inches in height. Fertilize infrequently or not at all afterward to keep plants compact and bushy. Too much fertilizer creates tall and gangly plants, and can cause fewer flowers.
Check for aphids frequently, and treat them with insecticidal soap. Treat powdery mildew during humid weather with an organic fungicide. Always spray pesticides and fungicides in the early morning or early evening to avoid burning the plants.