Evergreen Thyme?

I had heard that lemon thyme is evergreen here in zone 7, but see no mention of that in any of your thyme listings. Is there any such thing as an evergreen thyme? If not, could you suggest a low growing evergreen herb to be used as a ground cover for sun to part shade?

In warmer zones some thymes can persist like evergreens. Even in colder zones, some varieties stay green under the snow for several months; but the leaves generally don't survive the winter, and new leaves eventually take their place. In warmer zones, however, some of the upright thymes may survive through the winter without shedding their leaves. Generally, the creeping thymes are less likely to persist as evergreens through the winter as the shrubby upright types.
A key is the severity of your winter. If your area experiences deep freezes for weeks at a time, your thymes, even the shrubby upright types, will likely shed their leaves.