Here's my experience with 'walker's low'. It is in it's third year now---mine gets about 2ft high and the width has reached at least 3ft.

I enjoy it, even though it gets a bit bigger than what I was expecting.

I had to add my 2 cents, I clicked on this forum by accident, trying to go to the Northwest Gardening forum. I saw this about Nepeta though and had to add - Walker's Low doesn't mean the plant is going to be a low growing plant. It's just the name.

In zone 8 in it's second year, it's already waist high for me, and about 3 feet wide. Don't get me wrong - I love it - I think it's a beautiful plant. But ya better step back and give it some room.

I made this same mistake last year, I thought it was a low growing variety until someone on the cottage garden forum pointed out that was just the name.

Hope you find a place for it in your garden!
fiwa

Nepeta Mussinii (=Faassenii) is only 8-10" high and blooms most of the summer if cut back. It is very easy to start fom seed and will bloom the first year fom a March sowing
The ones I have came from JLHudson.