The Cosmea is usually sold as an annual ornamental plant and is not hardy. However, there are some species that are perennial and form root tubers. These can be overwintered in a similar way to dahlias.
How to overwinter a perennial Cosmea?
To overwinter a perennial Cosmea successfully, dig up the root tubers, store them frost-free and replant them after the ice saints. Potted plants also overwinter frost-free, are watered sporadically and not fertilized.
The perennial species include, for example, the chocolate-scented Cosmea atrosangiuneus. Because of its scent, the black-red flowering Cosmea is also called the chocolate flower. Dig up the root tubers and store them in a dry and dark place at around 5 °C. The cosmos are then planted back into the garden in May. Potted plants overwinter at the same temperatures, are only watered occasionally and are not fertilized.
Winter tips for perennial species of Cosmea:
- Dig up root tubers
- store frost-free
- plant again after the Ice Saints
- overwinter frost-free
- Water potted plants sporadically
- do not fertilize
Tip
When you buy your Cosmea, find out whether it is a perennial species, because only then is it worth overwintering.
