Amazingly, a potted rosemary (Salvia rosmarinus) that as a lark I left in the greenhouse for the Winter continues to live on. I did not expect this as we have had many nights where the temperature gets down to the single digits Fahrenheit. In the past, we have attempted to bring rosemary plants into the house to winter over but ultimately a variety of factors wound up killing them. This benign neglect is helped by the fact that even in the coldest of days, the greenhouse warms significantly. During a sunny day, the greenhouse will be 40 degrees F while the outside temperature is barely 10 degrees.
This temperature difference is also a characteristic of our unheated garage, which is often at least 30 degrees warmer than the outside. We keep a few tender plants in it near windows during this cold season. It is a bit inaccurate, however, to say that the garage is unheated as every time a car drives in its engine, which is over 200 degrees Fahrenheit hot, needs to cool off inadvertently heating the space it is in.
