When I moved to my current house, I brought along a potted rosemary plant that I had had for several years. It had always struggled thru winters because of the dry air from the wood stove, but it had always come back once the humidity started rising in the house.
However, the first winter here, it was doomed. Although pellet stoves (which I installed January 2014) don't dry out the air and I had humidifiers going, the house was so air porous that it was extremely dry in this house. The poor plant crisped up, dropped all its needle-type foliage, and never came back.
This past August or September, I stopped at the local Agway for some reason, and they had a couple of left-over seedling pots containing rosemary plants. Since all their plants were on sale, I decided to take one. I potted it up and left it out on the back porch until it got cold out, then placed it in the bathroom window. I had hopes that it would fare better than the last one because I've tightened up the house (less air leakage), it would be in a room that was humid at least once per day, and I had new windows installed the summer of 2014. What do new windows have to do with it? Well, the bathroom window is a "garden" window - which in effect is a tiny bay window. With a window covering in place that little area is a bit cooler and hopefully keeps a bit more humidity in that area.
Well, so far the plant seems to be happy and healthy. Although that window area is in the low 60's (I'm guessing - it is cooler than the bedroom, which stays between 65 and 67), the leaves have stayed green and wonder of wonders, it bloomed. I didn't even know rosemary had blooms as my other plant never did so. I couldn't get great pictures, but the blooms are tiny and by the time I saw them, they were past prime, with some dropped petals.
There was another stalk that had blooms that had already dropped all their petals too. Next winter, I have to remember to be on the look out for the full blooms.
EDIT: After taking the thermometer from the bedroom and placing it in the bathroom window for about 10 minutes (not enough time for it to truly stabilize), the temp is showing 59* - on a morning where it is 30* outside. I would imagine it gets colder as the outside temp drops.
That's an interesting experiment that you have going, there. In Green Thumbs, I need your help., I show the rosemary plant that survived a few winters in our warmer zone and, in a comment, you say that your own rosemary plant was 5 years old at the time (October 2013).
I doubt that the rosemary that I planted last spring will survive this winter. It isn't looking all that well.
Posted by: Cop Car | February 02, 2020 at 10:11 AM
P.S. I failed to say how pretty your current plant is and that I don't recall whether my previous plant was ever caught blooming (although, I want to say "yes".)
Posted by: Cop Car | February 02, 2020 at 10:12 AM
Is that rosemary inside? Mine have been potted, spending temps above 30* outside, then brought inside for colder weather. If yours is inside, what is happening that makes you think it won't survive?
Although rosemary can survive down to the occasional 10-20* temps, if the ground freezes hard, or there are a lot of temp swings, then it will have a tough time. It may eventually lose enough vitality that it can no longer survive. It is a Mediterranean plant after all.
Posted by: bogie | February 02, 2020 at 04:17 PM
Outside - under the edge of the back porched - not far from the Magic Plant.
Posted by: Cop Car | February 02, 2020 at 04:57 PM