The coldest room in our house is the little back hall by the kitchen door, and at 6:30 this morning the thermometer on its windowsill read 54 degrees. That's where the rosemary lives from November to April, in a 10-inch terra cotta pot beside a pair of rain boots and the recycling bin. It looks better today than any rosemary I've ever tried to keep through a winter.
In zone 6b, rosemary left outside is a coin flip. Some winters a plant against a south wall makes it, and some winters a week of single digits turns it brown overnight. Our porch rosemary is the one I snip for roast chicken all summer, and I didn't want to gamble with it, so it comes inside. That decision is easy. Keeping it alive indoors is the part I've gotten wrong twice.
Two rosemaries I lost
The first one came inside in the fall of 2020 and went on a sunny living room windowsill right above a cast-iron radiator. Our 1924 house is heated by old hot-water radiators, and they make the air bone-dry by December. That plant was crisp by mid-January. It never wilted first. It just turned to a gray, crunchy broom while I wasn't paying attention.
The second one, a couple of winters later, I tried to fix with kindness. I moved it to a cooler window, watered it often and misted it every morning because I'd read that it liked humidity. By February it was coated in white powdery mildew, and by March the roots had rotted. I'd swung from too dry to too wet without ever finding the middle.
What's different this winter
This plant came from the nursery last spring, spent the summer on the porch bench and came inside the first week of November, before the hard freezes. Before bringing it in I hosed it off on the porch steps to knock off anything hitching a ride. Here's the setup that seems to be working:
- A cool room. The back hall runs between 52 and 58 degrees most of the winter. We keep that radiator valve turned almost all the way down, so the air is cool but not desert-dry.
- Bright, not hot. The window faces east and gets a few hours of morning sun, which seems to be enough for a plant that isn't trying to grow much.
- Watering by weight. I lift the pot. When it feels light and the top inch of soil is dry, it gets a slow drink until water runs out the bottom, usually every 10 to 12 days. Rosemary doesn't droop to tell you it's thirsty, so the lift test is the only signal I trust.
- No misting. Never again.
- A quarter turn on Sundays so it doesn't lean toward the glass.
The tradeoff is that the back hall is dim compared with the porch, so the plant has barely grown since November. A few new tips came in pale and a little stretched. I've made peace with that. I'm not asking it to grow in winter, only to wait.
Waiting for April
The needles right now are a deep gray-green with silver undersides, the exact color of the "blue-gray" crayon that nobody in my classroom ever picks. Every time I walk past I rub a sprig between my fingers, and the hall smells like a Sunday dinner for a minute. Pim sniffs it occasionally and walks off unimpressed. He saves his enthusiasm for the cat grass on the kitchen counter.
In mid-April, around when the fig comes up from the coal room, the rosemary will start going out to the porch on mild days, first in the shady corner by the screen door and then back to its spot on the bench after a week or so. Rosemary that's been indoors all winter can scorch if it goes straight into full afternoon sun on a southwest porch, and I'd hate to lose it to impatience at the finish line.
I'm not declaring victory until it's back outside. February still has a week left, and March around here has its own ideas.
Next year: root two cuttings in September and keep them as backups on the same sill, so a coin flip never decides whether we have rosemary.
