Can rosemary survive outside over winter? The answer depends on your growing zone, as rosemary plants are unlikely to survive temperatures below 10 to 20 F. (-7 to -12 C.). If you live in USDA plant hardiness zones 7 or below, rosemary will only survive if you bring it indoors before the arrival of freezing temperatures. On the other hand, if your growing zone is at least zone 8, you can grow rosemary outdoors year round with protection during the chilly months.
However, there are exceptions, as a few newer rosemary cultivars have been bred to survive temperatures as low as USDA zone 6 with ample winter protection. Ask your local garden center about ‘Arp,’ ‘Athens Blue Spire’ and ‘Madeline Hill.’ Read on to learn about protecting rosemary plants in winter.
How to Protect Rosemary in Winter
Here are some tips for winterizing rosemary plants:
Plant rosemary in a sunny, sheltered location where the plant is protected from harsh winter winds. A warm spot near your house is your best bet.
Prune the plant to about 3 inches after the first frost, then bury the plant entirely with soil or compost.
Pile 4 to 6 inches of mulch such as pine needles, straw, finely chopped mulch or chopped leaves over the plant. (Be sure to remove about half of the mulch in spring.)
Unfortunately, there is no guarantee that your rosemary plant will survive a cold winter, even with protection. However, you can add a bit of extra protection by covering the plant with a frost blanket during cold snaps.
Some gardeners surround rosemary plants with cinderblocks before adding mulch. The blocks provide extra insulation and also help hold the mulch in place.