Cosmos ‘Sensation’ brings long-lasting colour to Cornish gardens when started indoors in spring. With early sowing, pinching out for bushy growth, and regular deadheading, these bright annuals thrive in sunlit borders, flowering freely into autumn with minimal fuss.
Cosmos ‘Sensation’ has become a border favourite for its ferny foliage and vibrant blooms that last right through the season. In a Cornish garden, where mild springs and soft summers meet the salty air, cosmos offers a generous display — if you give it the right start. Here’s a gardener’s guide to sowing, growing, and keeping these annual stars flowering into autumn.
Begin cosmos indoors 4–6 weeks before the last frost (usually March–April in Cornwall). Sow into trays or individual modules using fine, moist seed compost.
Once the first true leaves appear, prick out into pots if needed, keeping seedlings in cool, light conditions. Gradually harden them off over 7–10 days once the frost risk has passed.
Transplant into sunlit, sheltered borders with well-drained soil. Space plants 30 cm apart — this gives each plant room to fill out.
Pinch out the growing tips once planted to encourage bushy growth and more blooms.
Removing the top shoot when plants reach 10–15 cm tall stimulates side shoots, leading to a bushier shape and many more flower heads.
Cosmos thrive in the mild, light-rich Cornish climate — especially when given a free-draining soil and regular deadheading. Pinching out and spacing well turn a few plants into a border of billowing colour that lasts right into autumn.
