One of our customers emailed us about her herb garden. She wanted to know how to protect her lavender and rosemary for the winter. Both of them were planted in her garden this spring. It was a good question and I thought others might enjoy the answer:
Lavender is hardy to at least 6500′ and I know of a few lucky gardeners who get it to survive the winter at 8000′! I think at your elevation (4900′) your lavender plant should be just fine, but if you have any rocks to put around it, they can offer additional protection. Rocks collect heat, keep the soil underneath moist, and stop the plant from heaving out of the ground during freeze-thaw cycles. A rock the size of a softball is not too small, a rock the size of a basketball is not too large. Lavender comes from the Mediterranean where winters are cool and wet, not cold and dry. The rain we got over the weekend was perfect! Don’t let your lavender go into the winter too dry. On the other hand, watering it when the ground is frozen accomplishes nothing. I’d check for moisture around Thanksgiving and if it seems dry then, give it a drink. Check again in mid-January if we have a stretch of warm open weather. Don’t prune it until next spring, and then only remove dead branches. Cutting it back too hard can be the death of it!
As for your rosemary, rosemary is not really hardy outside along the Colorado Front Range. Some people get them to survive by planting them in a protected courtyard, or in just the perfect micro-climate, but it’s not a sure thing. If you don’t want to dig it up and bring it indoors, you might try the rock mulch and, in addition, try protecting it with pine boughs. I’d wait until Halloween, and then cover it with three or four evergreen boughs. And if you hear the weather is going to be extremely cold, like below zero cold, you could cover the boughs with a sheet or big box and then a sheet.
Good luck.
