Most herbs taste much better fresh, and rosemary is no exception. That’s why every winter I try to keep my rosemary alive in a pot inside the house. Rosemary is not reliably hardy north of zone 7, so while southerners can grow this in the ground and watch it take on shrub-like proportions, we cold climate gardeners must bring it into our houses and attempt to give it the equivalent of a southern winter indoors, or it will never really get big enough to harvest from regularly.
It’s not easy, let me tell you. More than one northern gardener has finished the winter with a dead rosemary plant. To succeed with any plant, a gardener thinks about its native range and tries to approximate those conditions. Rosemary is native to the Mediterranean basin. This is where many people make their first mistake. They hear that rosemary is drought-tolerant, and they let it dry out. But as Nancy Szerlag, Detroit News gardening columnist states, “a dry rosemary is a dead rosemary.” What people forget is that the Mediterranean climate receives almost all its yearly precipitation during the winter. The rosemary wintering over on a windowsill still expects it to rain.
That same Mediterranean native thinks winter is significantly cooler than the typical furnace-heated northern residence. Judy Miller, owner of Paradise Gardens Rare Plant Nursery and occasional contributor to this website, says, “I either keep it on a barely heated sunporch so it doesn’t go below freezing or above 50, or against the coldest window in a cold room.” No habitable room in my house stays below 50F in the winter, but some rooms are definitely cooler than others. Those are the rooms I consider for the rosemary.The last consideration is light. Rosemary is not in active growth at this time of year, but it is still accustomed to full sun in its native land. It is happiest in a south-facing window, though even then its growth is spindly. Nancy Szerlag has grown hers under shop lights four inches from the fluorescent bulbs. C.L. Fornari, a writer, professional speaker and host of GardenLine on WXTK radio, learned that some varieties of rosemary are easier to winter over than others. In particular, ‘Salem’ is less sensitive about hours of daylight when it’s resting. C.L. adds, “‘Salem’ rosemary puts on a growth spurt starting in late-January or February, when there isn’t enough sun to make that new growth thick and strong. If you pinch this weak and spindly growth in half when it’s about three inches long the plant will then put out additional sprouts when you put it outside in the spring, and this new growth will be thick and robust.” I don’t know what variety my rosemary is. It was just a generic rosemary plant, rescued from the herb section of a big box store. My rosemary also puts out this weak growth, and I give it a good haircut once it is acclimated to the great outdoors again. That is, it gets a good trim when I don’t nearly kill it leaving it outside in the spring. There seems to always be one spring morning that gets a lot colder than I expect, and I have pulled this rosemary through the winter at least twice, only to almost lose it to a late spring frost.
Where to find named cultivars of rosemary
You can find rosemary in the spring almost anyplace that sells vegetable seedlings. However, if you want to get a specific cultivar, such as ‘Salem,’ you will probably have to order through the mail. Papa Geno’s Herb Farm has an extensive selection of rosemary varieties, including ‘Salem.’ I’ve never tried them myself, so if you have experience with them or have your own favorite source to recommend, please tell us all in the comments.