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  What about Aquarius and Capricornius? They were never drawn. Plants are not born or grow in winter. 
  There is an obvius correspondence between stars and plants.

I think this is better than some of the suggestions people have given, but there are actually plants that grow in the winter, such as some of the plants from the cabbage family. They can even grow where there is mild frost and light snow and I'm quite sure people did grow them because there were no supermarkets in those days.

Also, plants grow all year round in the milder or warmer parts of the Mediterranean.