Many thymes are indeed hardy in zone 3, but creeping thyme (Thymus serpyllum)is rather tall and vigorous for between stepping stones (it gets to about 8" tall in flower here)... I'm puzzled why it's so often recommended for that use. Woolly thyme (Thymus pseudolanuginosus) is much shorter, but also quite vigorous; it would work in a pinch, but would need plenty of cutting back. What I've found works nicely between our flagstones is the very tiny-leaved varieties of thyme (along with some other very low ground cover plants of different species)... I'm using Thymus praecox 'Elfin'; slow growing and less than a centimeter tall. Works for me, anyhow. Hope this helps.

I have Thymus-elfin Elfin thyme that is hardy down to zone 3. It is a dwarf thyme only 1" tall. I have it between stepping stones and grows just fine. In one year it filled in beautifully. I got it at Bluestone Perennials. I had tried others and they didn't make it.

Here is a link that might be useful: bluestone

I've put down pavers and have space in between that I thought I would put in either Creeping Thyme, Wooly thyme or Blue Star Creeper. I live in an area where we can get a pretty large amount of snow in the winter. Are these hardy enough to come back each year? Or, does anyone have anyother ideas of some type of plant I can use.

The creeping thyme that I grew from seed gets too high, as noted above, and self seeds and spreads by rooting from stems so I would not use it between pavers. I use mine as an edging and it is very vigorous and needs pulling up to keep from taking over the bed. Now I cut mine back just as it blooms in the area where I put it between stepping stones so it won't self seed. Eventually I will replace it with Elfin or another very flat growing variety which I have in another area.

Wooly thyme is flat and not overly aggressive for me so I might consider using that.

Both grow well after the snowy winters of MN.

I love my variegated lemon thyme I'm growing in the front flower bed of our house. Just running your hand through it brings up a strong lemon smell, and it grows FAST. Left untrimmed, mine has so far grown ~4" tall, but will be cut back soon for making dried herbs for the spice rack (yummy).

Here is a link that might be useful: Lemon thyme

I've used several thymes and love them, they are hardy! Creeping thyme here gets about six inches.

I have only a wooly thyme that I planted in the spring between my stepping stones. It has about quadrupled in diameter, but it still hugs the ground. I am told it is hardy here.
jan