First year they sleep, second year they creep, third year they leap.

Or if they are in my yard some of them have taken four or five years to leap.

Clematis are far from being instant gratification plants. They are very long lived though once they get going.

The Type III viticellas are much faster getting going than the IIs. I have three year old viticellas that are bigger and lusher and have more flowers than ten year old type IIs and it isn't just that they are expected to be different sizes though there is variance in size between cultivars.

Assuming good soil, water, fertility - you will see more next year, and maybe this year, too, on new growth. You can deadhead those two flowers to stop the energy from going into seed production, but they do take some time.

The Loew's clematis will not be as mature as the ones from Silver Star, so you're ahead of the game with your coming shipment.

It's not just BorS's yard. Some clematis just take longer to mature.

The location variable cannot be overemphasized. I planted some last year in a prime, sunny spot where they flowered well in year 1 and this spring, in year 2, are 7' tall and have multiple vines and many buds.

Another was planted 3 years ago in a less desirable location and now, in its 4th spring, has only two 4' vines. It has recently been moved to a spot with more sun and less competition.

In both cases the plants were purchased in 1 gallon pots.

I have found soil prep/root competition from trees to be a biggie as well.

I have areas with neighbor's tree roots and areas that we didn't amend or even dig much at all and just plunked plants in with post hole digger vs. areas where entire beds were amended heavily.

The Clems without roots and with heavily amended soil are doing much, much better.

Since my garden/lot/house for that matter is very small I'm now going to go back and dig up stuff and amend like crazy and perhaps insert some buckets to try to keep tree roots away from Clemmies. Another poster here has done that with success.

I do not want whole sections of yard to be without Clemmies especially when there is a long fence for them to climb on but soaker hoses and top dressing with compost annually have not proven to help, some are still scraggly and pathetic at five and ten years old and not all Large Flowered Type IIs.

Just anecdotal, but my clems from:

A reputable local nursery - 1 died, 1 leaped in its 4th year

Bluestone - 2 leaped in their 2nd year

Lowe's - 1 in its 3rd year now and is gearing up to be another dog year