A family member collected a mystery seed off a plant with gorgeous flowers but couldn't remember what they looked like so I planted it (3 years ago)to see what would happen. The seeds looked like clematis seeds and the leaves look a lot like my clematis montanas. The first two years the growth was slow and small. This year, however, the plant has exploded. The last picture of the three posted below was taken in April and the preceding two photos are the plant today. I haven't seen any blooms yet but the plant roots and spreads easily via the vines sprouting roots where they touch the ground. I fertilized the ground with steer compost before I transplanted the plant this spring but haven't added any more fertilizer.

I'm starting to get worried about the plants' voracity. I want to hang in there and see if it blooms next spring (assuming it's like a montana). Is it unheard of for a new clematis not to bloom at all until year four? Have I unwittingly planted something invasive for my area? I haven't had much luck id'ing this via pictures, especially since I don't know what the flowers look like.

I would appreciate any help or advice you can give me. Thank you!
{{gwi:611349}}Mystery Clematis