Tuesday, March 5, 2013
For many years, I had at least one rosemary plant which I would take indoors for the winter. On the whole, rosemary bushes do not like spending the winter in a dry house. In such an environment, they hold on to life for a year or two, but soon give up the ghost.
A few years ago, I discovered that the most important way to succeed in overwintering a rosemary plant is to make sure it is stored in a humid-enough environment. Strangely, for a plant that originates in the Mediterranean, it can actually do without light for months, but not without humidity. I discovered that when I was going away for the good part of a winter. In late November, I potted up my rosemary and stored it in a crawlspace where there is no light, quite a bit of humidity and temperatures that do not reach the freezing point. I had little hope that the plant would survive but, to my amazement, it came out in the spring looking much better than it ever had done after a winter indoors. All it needed before another season out in the garden was a bit of trimming.
Another thing that might help a rosemary survive the winter is to keep it potted when you bury it back in the garden in spring. This gives you more work in summer as it will require more watering than if it were planted directly in the ground. When you put the plant in the ground in its pot, watering is trickier. The whole purpose of doing this is that, in the fall, when you dig up the pot to take it in, the plant is under much less stress as the root system is not much disturbed.
A rosemary thus treated will last a few more years. However, the yearly taking-in-and-out remains stressful, and eventually the shrub cannot take it anymore. This year I am making a new experiment. In the past, I have tried leaving a rosemary bush outside with lots of protection, but it did not work. The cold wind made short work of it. This winter I bought a creeping rosemary (Wilma's Gold - the label says hardy to zone 6 but I think this rating is optimistic). I plan to leave it out in the ground with a lot of protection. My reasoning is that since it will "keep a low profile", not sticking out of the snow, it might just make it covered with a thick insulating layer. After all, since Agapanthus does survive the winter in the Bruce, a ground-hugging rosemary just might make it. Hope springs eternal in the gardener's breast!