The top likes to be in full sun, usually, but the roots like it cool, so having something around the base to shade the root area is helpful.

I only have 3 and they're relatively new, so mine aren't too big yet. But I do have them planted like I mentioned and they're growing.

Gail

They also like lots and lots of water. I wonder if your sandy soil is preventing them from getting enough water? You could try one in a container, although you may have to water it daily as containers tend to dry out so fast.

with very sandy soil, you might do well to lift them, remove an shovel or two of the existing dirt, and add a handfull of the (well-soaked) water retention crystals, a handful or three of compost, and a handfull of fine mulch. stir it all in to the hole, reset your plants, backfill, water, and mulch heavily.

that being said, if you lift the plant, and find it's still in the shape of the pot you took it out of, then take a matt knife, and slice into the rootball in three places to open it up. that should allow new roots to start growing outward.

if it is putting out new roots on its own, handle it gently, and you should get SOME new growth next spring... I put three in, and the spent the first two years sleeping, building up their reserves. this is totally normal- they're only flowering in the garden stores because they're FORCED to, and it usually exhausts them.

Enrich the soil with lots of organic matter - in fact, they would probably adore having their own 2x2' lasagna-style bed, although since your soil is already sandy, you could probably just dig down about a foot and then lasagna upwards until it's several inches above ground level. They do want their roots well-shaded and are quite happy with a thick layer of shredded leaves for mulch (which will decompose to further enrich the soil). I mulch mine heavily in the late fall to help protect through the winter, and top it off in the spring -- be careful not to smother the crown. Although it varies, most clematis seem to want a year or two to establish their roots before they get to the business of blooming. Also, don't forget to prune appropriately for the plant's category.