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What is the best way to overwinter these lovely plants? Mine are still gorgeous clumps of flowers at the moment but I know from bitter experience that winter weather will be a big problem. I have an unheated greenhouse and I also sew wool-and-hessian bags for the protection of my container plants but neither of these methods seem to suit cosmos! They are in large pots currently. Should I bring them into the house?









Normally a greenhouse should be fine. When you say the house, have you a conservatory? If kept dry choc cosmos should survive. Are vine weevils the culprits? Can you try fleece? Are you in very cold part of the country?

I keep mine in my cold greenhouse- kept dry and covered with fleece

Pam LL x

Gary Hobson

It's important to understand that fleece does NOT protect from prolonged cold. Fleece merely reduces the rate at which the interior of the greenhouse cools down (or warms up). If the temperature outside is sub-zero for several days on end, then that is the temperature that the interior of the greenhouse will stabilize at.

Pam is an expert on overwinting tender plants, but she lives in a built-up area, in the South of the country, so her garden will be several degrees warmer than many of us.

The problem is unpredictable too because we just don't know what the coming Winter will be like. It may be mild; it may be colder than last year.

I have some chocolate cosmos in a pot. Mine will be overwintering in the spare bedroom.

Gary what fleece does is help keep plants a degree or two warmer. It can make a difference and does in many cases. ,if we have a severely cold winter fleece may not make a difference. Wrapping pots outside too only makes a limited difference but it's still worth doing..usually. Ii have scores and scores of tender plants..they ain't going in my bedroom The temperature of the greenhouse will be colder than that in the microclimate provided by fleece



I too grow mine in a large pot too. Am in Nwest & by the end of this month the pot will be well wrapped with bubble wrap, to protect the roots from freezing. The plant will be cut back, if not already frosted on top, & the whole put into either an insulated coldframe or into an unheated porch. Either way the whole covered in fleece. Compost allowed to stay almost dry over the winter months & I restart the tuber in some MP compost next March. Works for me, cant keep them in the ground over winter up here, but this tuber is several yrs old, J.

Thanks very much to all who replied. The general view seems to be to lift the cosmos or wrap up if in containers and then possibly move them to the greenhouse and keep them dry. A bit like dahlias? I have always found them so gorgeous but temperamental!

I think one of the key things is to keep them very much on the dry side, as well as protected as is practical for you through the cold months. I finally lost my venerable chocolate cosmos through the last winter, but it was vine weevil grubs that did it!
I had it for about 7 years, every spring I thought I'd lost it, always surprised me how late it was to show signs of life.

Put the pot in unheated greenhouse in late October-ish. Start watering again in late March or so and bring out when the waether warms up. I have two 8 year old pots that have survived under this regime.

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