Keeping rosemary in pots is the only way to have year-round rosemary in our climate. Bringing plants indoors over winter means a bit of special care however. Our houses are too hot and dry, the opposite of what a rosemary needs: a cool, slightly moist environment. Here are some tips:
1. Have your rosemary growing in a large size pot. If you are buying a plant now, the larger, the better. Four inch pots can dry out too quickly. If you are overwintering a plant you already have, take note that the more established your plant is in the summer, the more likely it will last over the winter when you bring it in. Plants that you dig up out of the garden in the fall are less likely to live through the winter.
2. Soil should be well drained. Add sand, grit, and peat or coir to the mix.
3. Water thoroughly, then let almost dry out, but don’t let it get bone dry.
4. Keep pot in a large, deep saucer with a 1″ layer of aquarium gravel, so that drained water will evaporate, keeping air moist around the plant. But don’t let the pot ever sit in water above the base of the pot.
5. Keep it cool. 60F or 15C. An unheated sun porch that stays above freezing is ideal. If you have deep windowsills, closing the drapes at night so that the plant enjoys the cool air next to the window can help.
6. Bright sunlight, a south or west facing window, for best results.
7. Although moist air is ideal, keep the air moving with a fan (on low), to stop any mildew forming on the leaves. This is a good tip for all your plants.
It’s true that herbs can be tricky in our modern houses, but it’s well worth giving it a try. Snipping off your own sprigs of rosemary for your dinner casserole is one of life’s greatest pleasures, especially in the dead of winter.