Growing Rosemary in Zone 5

According to the hardiness maps we are too far north (zone 5) to grow rosemary as a perennial. So I thought putting a rose cone over it might help it make it through the winter.  Is that a good idea?  I put it on after we had some pretty cold weather, and when I put it on, it still looked green.  What do you think?

Rosemary is generally hardy in zones 8 and 9.  A few cultivars like Arp and Hill Hardy will survive in zone 7 and a few gardeners report success in zone 6b.  Check out the National Arboretum located in zone 7 for more details on their rosemary hardiness study.  You may chuckle when they talk about their challenging winter which is much milder than those gardening in zones 2 through 5.  You have nothing to lose by trying the rose cone.  You may need to vent the cone on sunny days when the temperatures inside the cone can cook the plant.  Be sure to remove the cone when spring temperatures start hovering above freezing.  Next fall consider bringing a plant indoors.  Though challenging to over winter inside you have a better chance for success and even the dried dead plant is fragrant.  

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