Did you prune them in early spring? All Clematis should be hard pruned the first couple of years to get them off to a good start.

Did you plant them deeper than they were in the grower pot?
Early large flowered hybrids should be planted 3-5 inches deeper.

Yes, they should be fertilized, most of us use organic rose fertilizer or compost/composted manure/alfalfa pellets. Not something quick acting for annuals like Miracle-Gro.

Clematis also benefit from large holes, well amended when they are planted.

They also all take at least three years to reach maturity.

You don't have to shade their feet. That is a mistake in translation, meant to say moist feet.

Mulch will help keep the soil evenly moist and keep weeds from competing with your clematis. Follow BorS's recommendations for fertilizer and then be patient. Once out of the nursery situation, clematis need to take time to establish a solid root system before the top parts of the plant start looking robust. Also, in my experience many of the early large flowering kinds are a bit fussier in general and not all of them are robust by nature, while more of the later flowering ones seem to be easier and more robust. Clematis teach me patience, but are really rewarding to grow.

You're not the only one Nancy! I have a Henryi clematis that I planted in 2009 that is still just sitting there this spring! He's about 6 inches tall! I have never yet seen a bloom or seen him get any larger!
Now, I did hard prune him the first couple years, fertilized in spring, kept him watered well, everything I could do. Nada, zip
So, if he doesn't perform better the rest of this year, I have decided to either say the heck with him and let him be the tiny, lazy thing he is, or to replace him with Huldine! lol
He better wise up (and I mean UP lol) or he may be toast!

kentstar

I'm still trying to get Henryi to perform after 4 years. One bud this year, previous years, nothing. I'll take a photo of the bud, and then 86 the plant. I need the space for the reliable bloomers that I have in pots.

What everybody has said is true, but I'll add that I'm getting a lot of unusually small flowers on established clematis after two months of spring drought. Weather can make a difference.

First year in the ground plants will start off slowly and it takes some time to get the roots established. By the end of the summer you may or may not have good vine/leaf growth and a few blooms, depending on the variety and the size of the clematis when you planted them. A plant in a gallon pot full of roots will grow more than a plant in a small 4 inch pot or a starter plant in a gallon pot but few roots.

The first year they sleep, the second year they creep and the third year they leap.

The plants you bought from the garden center were grown and pruned or pinched to look full for sale. They often have only one stem and the vine has been twined through a support to look fuller than it actually is. They are also green house grown which will account for flowers and buds that may not be in sync with their natural cycle. Ever notice how late bloomers often have buds or blooms in the spring when they are sold?

The plants purchased from the garden center have been fertilized heavily too because many won't purchase unless blooming....

Thanks so much. I didn't hard prune (or at all!) . I will this year. And if I planted too high - which I did- should I replant when dormant or build soil up around plant? I will mulch. That's the easy one.
Thanks, nancy