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- You can't plant them outdoors until the last frost has passed
- Last frost is around mid-April in most of the UK, up to mid-or-late-May in colder inland Northern and Scottish gardens.
Annual cosmos are extremely popular bedding plants and cutting flowers that bloom their socks off from May until Autumn, lasting for up to a week in a vase. They are easy to grow, ideal for containers, pretty much pest free, reaching 60-90cm tall.
We sell Cosmos seedlings in jumbo plugs. They arrive well-rooted, and ready for planting or potting.
Your seedlings must be unpacked, watered, and either plants or put in a sunny place as soon as they arrive. If planting will be delayed, water them every 48 hours, but do try to plant them ASAP.
Please note that mail order annual plants are not covered by our guarantee, because they are supposed to last less than a year after you receive them.
- Order now, pay later: we don't charge your card until before delivery
- When your order is ready: your seedlings are delivered by next working day courier (not the next working day after ordering!)
- Friendly support: if there is anything wrong with your plants when you inspect them, Contact Us within 5 working days
What are Cosmos?
Cosmos bipinnatus AKA Mexican Aster
- Uses: Annual bedding & wonderful cutting flower
- Plain and variegated pastel colours in white, pink & yellow
- Flowering: May to September,
- Position: Full sun with decent, moisture retentive soil
- Growth: Up to 90cm
- RHS Plants for Pollinators
Planting Cosmos
Plant so that the top of the plug is 1-2cm below the surrounding soil level, which will help to stop it drying out.
Space plants 25-35cm (8-14") apart: wider spacing will encourage sturdier, more wind-resistant stems.
In windy, exposed locations, a bed of cosmos benefits from a horizontal netting support stretched over them at about 30-40cm above the ground (or even two nets, one at 30cm and another at 60cm). It looks bad when you install it, but the Cosmos quickly grow through and hide the netting.
A small quantity of plants could be staked individually with bamboo canes.
Growing Cosmos
Cosmos like a well-worked bed with nothing special added, only a bit of compost, as they flower best on averagely fertile soil; rich soil will produce more leaves than flowers.
They need a lot of sun, and although fairly drought tolerant, they still need water in dry spells to grow and to flower.
To help them bush out and produce as many flowers as possible, the tips should be pinched out when they are about 20-30cm tall.
Cut or deadhead the flowers promptly to extend the flowering period.
To maximise flower size and colour, feed lightly with a high potash and phosphate fertiliser during the growing season.
Buying Cosmos
Our Cosmos are sown under cover in early spring, into 6cm x 4cm Jumbo plugs, which are the best value.
- Cosmos are available as single plugs, but buying in packs of four gives you better quantity discounts.
Delivery is when the plants are ready and the weather permits, generally from the beginning of May onwards. We email you when your order is placed with an expected timeframe.
We grow our plants from the best quality seed, in peat-free compost with a slow release fertiliser.