Hello Gardeners, I’m Amanda McNulty with Clemson Extension and Making It Grow. When ancient clubmosses in the family Lycopodiacaea were growing in what is now the coal fields of West Virginia, over 300 million years ago during the Carboniferous period the weather was much warmer and carbon dioxide levels vastly greater than today. Sometimes carbon dioxide is a limiting factor in plant growth – the ancient relatives of today’s clubmosses, plants like running cedar, grew to enormous heights of