When to sow Cosmos?

Cosmos thrives in full sun and tolerates poor to moderately fertile soil, making it one of the easiest annuals to grow. It performs best in loam or sandy soil with good drainage; overly rich soil encourages lush foliage at the expense of flowers. Choose a sunny, open spot where plants will receive at least six hours of direct sunlight daily. You can sow cosmos directly outdoors from April onwards, once the risk of hard frost has passed, or continue sowing through May and June for successive blooms. Prepare the soil by removing weeds and raking to a fine tilth, but avoid adding compost or fertiliser—cosmos actually flowers more profusely in lean conditions. Sow seeds thinly, scattering them on the surface or pressing them lightly into the soil; they need light to germinate, so cover with no more than a few millimetres of fine soil or vermiculite. Space sowings or thin seedlings to 40 cm apart to allow good air circulation and room for the plants to bush out. Germination typically takes seven to fourteen days. If starting indoors in modules in April, transplant seedlings outside in late May after hardening off for a week. Water gently after sowing to settle the soil, but thereafter cosmos needs very little attention. Avoid overwatering, as these plants are naturally drought-tolerant. Taller varieties (up to 150 cm) may benefit from light staking or planting in a sheltered spot if your garden is exposed to strong winds, though their wiry stems are surprisingly resilient. No mulching is necessary.