If you are talking about "Home of Clematis" here in British Columbia most of the clematis in my garden have come from them. This is where all the retail outlets around here get their clemies from. When I bought most of mine they hadn't started up the mail order side of their business.
At times the garden shops in my area have starter plants in small pots from them but I've bought mostly in one gallon pots. I have to say the small 2.5 pots all looked very healthy but in my opinion they need to grow a year or two in gallon pots before planting out.
I hope to visit their greenhouse next spring, I still have a few spots I can plant another clematis.
I've never heard a bad thing about them or their plants and have always had good results with the plants I've bought from them.

Annette

Oops! That's exactly who I was asking about. Thank you so much for the information. They have a great selection of clematis, I think.

Wow they have a lot of clematis to choose from !
Another one not spoken much of is donahues , I believe from Michigan . They also sell quite a variety!
And brushwood of course , and joy creek clematis .
Anyone have any others to suggest ?

Donahue's is located in Minnesota. I visit them in the spring for their open house to pick up new clematis. I also buy mostly gallon pots but have had good success with their smaller plants which I pot up to a gallon container and grow on until fall or the next spring.

They also sell wholesale clematis to nurseries and to growers for big box stores in our area.

The small clematis plants that I have ordered from Donahues and from Brushwood have been well rooted and arrived in good condition.

Here is a link that might be useful: Donahues

Silver Star Vinery in Washington state is another one that ships 1 gallon size plants.

Here is a link that might be useful: Silver Star Vinery