By Raysmith
United Kingdom 
are all cosmos plants pernial if so which survive our winters the best
22 Apr, 2013
Answers
Some, including the chocolate cosmos, are hardy perennials in Zones 9 and up, but most of the UK is Zone 8.
22 Apr, 2013
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Very few of them I'm afraid. One that is, is the chocolate cosmos but that is difficult to keep going over the winter. I have lost two in successive winters and a neighbour who probably knows more about them than I do, having worked at a nursery, lost her chocolate cosmos last year.
22 Apr, 2013