Can Cosmos Survive Winter?

HARDINESS: Chocolate cosmos are tender perennials and winter hardy only in zones 9-11. If the plants are grown in very well-drained soil and are heavily mulched, they may survive the winter in zones 7-8. For best results, dig the tubers in fall and store them indoors for the winter where they can be kept cool and dry.

Do cosmos come back every year?

Cosmos are half-hardy annuals that grow, flower, set seed and die all in one year, but unlike hardy annuals, they can't withstand low temperatures. ... To give your cosmos as long a flowering season as possible, sow the seeds early, indoors, in March or April.

How do you overwinter cosmos?

Cosmos atrosanguineus (chocolate cosmos)

Uncover the plants during early spring when the worst of the frosts are over. In colder areas, after the foliage has died back in autumn, reduce the stems to within 5cm of the roots. Lay in a tray of soil or compost and over-winter in a frost-free environment until early spring.