Potted Rosemary Left Outside in Snow: An Update
I thought my experience with leaving a few herbs, especially rosemary, outside in very cold weather might help answer some questions many people seem to have about hardiness and when to bring plants inside.
As I mentioned in an earlier post, I brought most of my potted herbs inside in October, just before our first frost. But, I left a few plants outside in pots until last weekend, when I finally brought them inside. Being in Zone 5 in NH, weÂve had below freezing temps since 25 October and temps have gotten down to 12F/-11C with three measurable snowfalls. All the pots were frozen solid and snow covered. The plants were: a standard rosemary, about three feet tall, a dwarf, prostrate rosemary, Blue Boy, a pot of Profusion chives and a lemon verbena. When I brought them in the rosemary plants looked fine, the chives had died back to the dirt and the lemon verbena had dead leaves. I thawed the pots and the rosemary plants went right into south-facing windows. The chives went into an eastern-facing window, trimmed of all their dead leaves, of course. The lemon verbena went into the basement.
One week later the rosemary plants look very healthy with no signs of damage. Tips are green and thereÂs new growth on all stems. The chives also look fine and are already putting out new growth. The jury will be out on the lemon verbena until probably March, but I think it may be toast, since it really doesnÂt like to freeze. We shall see, but thatÂs what experiments are all about.
So, it looks like rosemary can take some pretty cold weather, even in a pot, and just shrug it off. I will try to put them out earlier in the spring, too, since they really seem to prefer it outside. Why did I bring them in when I did? Because temps got down into single digits the next night, and I felt that that was pushing it for potted plants. I do have a Madeline Hill rosemary and an Arp rosemary in the ground in a protected spot on the southern side of my house to see if they can take below 0F temps, but thatÂs another experiment.
As for the rest of the herbs that I brought in last October, everyone seems to be doing fine, even the basils. Some plants, like Mexican tarragon, African and holy basils, and VickÂs plant are even blooming.