I keep 10" pots of rosemary thru the winter.
The 1st few winters, they stayed on the floor of my basement. That room is probably about 55F at the coldest. If the sun shines during the winter afternoon, sunlight falls on that part of the floor for an hour, or so.
It survived reasonably well there altho' the last winter it was in the basement, I probably lost half of the plants
.
I felt it needed another location. For the last 3 or 4 winters, the rosemary has been on the floor of my unheated greenhouse. On nights when the
outside temperature is forecast to fall to 15 or below, the plants are covered with a quilt - actually, a folded vinyl tablecloth, now. If the temperature won't be above 15 - the plants will stay covered thru the day. I just needed something to guide me and chose the 15
outside temperature. It has worked. The fabric against the concrete foundation has frozen at times but still seems to keep the pots from freezing. Whatever the case, no plants have been lost since I've started doing this.
The rosemary had some problem with mildew last spring. Probably, that old quilt would be a better choice than the tablecloth. The plants came out of that after a couple weeks in the fresh air.
Steve
