squirrel ... I've experimented in the past using hay bales placed into long rectangles covered with plastic with holes with space inside to place covered and uncovered containers. This system works just fine. What I found was heat retention in the coral is sufficient for sprouted containers to have their tops completely removed very shortly after sprouting even in the coldest and hardest freezes. At the same time, you'll still want to keep the tops on the unsprouted containers to have a more ideal greenhouse effect going until they pop. The real key to success with this method is to make sure the plastic top is constructed to be easily and effectively adjusted to increase or decrease ventilation in the compartment space according to fluctuating direct sun and temperature conditions. I do think you'll find the coral will make for a very nice appearance. Good luck.