Woolly Thyme in Zone 5

We live in Parry Sound, Ontario, Canada and last fall installed a walkway of irregular stones. Our intent this spring is to plant woolly thyme between the stones. We are now having second thoughts as to whether or not this plant is hardy in our zone.

Woolly thyme is hardy to zone 5. Since Parry Sound is supposed to be in zone 5a according to the zone map in Chatelaine's Gardening Book. This may be too optimistic for some winters. However, since you live very close to Lake Huron, the water will damp out fluctuations in temperatures and in most winters you should not have any problems. The woolly thyme planted in zone 5b in my garden in Goodwood grew well for several years, but did not survive the snowless cold winter we experienced some years back – but we are about 30 miles north of Lake Ontario. A layer of straw as winter protection might have saved the plants.
I would play it safe and plant 'Orange Spice' thyme, creeping thyme, the somewhat taller wild thyme or some of the other plants we recommend. Check our web-site <www.richters.com> under "Q&A" click on "Search Q&A" and then type in "groundcovers" for lots of suggestions.