All about growing Cosmos from seed

Growing Guide

Cosmos will put on a continuous display throughout the summer months and well into autumn, standing on tall, slender stems which sway in the breeze creating that gorgeous soft and floaty effect. Perfect for a sunny spot in any mixed planting scheme, not only will they look great in the garden and be beneficial to pollinators, but they make lovely cut flowers too. Despite their delicate looks, these plants are pretty tough and will stay standing in rain or a drought.

Sow Cosmos seed indoors from February to April at a depth of 3mm in a good quality seed compost, and cover the seeds with a very fine sprinkling of vermiculite, or compost. Place the seed tray in a propagator or seal it inside a polythene bag, keeping the soil damp but not wet until gemination. Do not exclude light as this aids germination. When seedlings are large enough to handle, transplant into 7cm pots and grow them on in cooler conditions until large enough to plant outdoors. When Cosmos plants are well grown and all risk of frost has passed, acclimatise them to outdoor conditions over 7 to 10 days. Transplant outdoors in full sun in any moist, well drained soil at a distance of 45cm apart.

Alternatively, direct sow Cosmos seed where they are to flower in May. In a weed free area, sow seed thinly in drills 3mm deep. After germination and when the plants are large enough to handle, thin then to 45cm apart. Water regularly, until the pants are established.

  • Key Information

    Height: to 100cm

    Spread: to 60cm

    Half-hardy annual

    Full sun

    Germination: 7 - 15 days

  • Sowing & Growing Schedule

    Sow Indoors: February to April

    Sow Outdoors: May

    Plant Out: May

    Blooms: July to October

  • Varieties we recommend

    Fizzy Rose Picotee

    Velouette

    Purity

    Sensation

    Xsenia

    Apricotta

Top Tip

Create impact in your borders by planting multiple plants near to each other creating the effect of a single large plant. Pinch out the growing tip of each stem when transplanting to encourage stems to branch and produce more Cosmos flowers.

Deadhead faded Cosmos flowers regularly to encourage more blooms to be produced throughout the summer.