I grow them. They last longer in pots for me than in the ground. They are not 'live forever' plants and eventually you will be buying some new ones, but they do last for years and years. No matter where you grow them they need very good drainage - think cactus mix or gravel with just a bit of soil thrown in. If you grow them in pots you can move them out into full sun during the winter and into the shade during the summer. They seem to do the most spreading when buried under snow which is odd for such a juicy little plant.

I ordered a bunch from Squaw Mountain Gardens about five years ago and most have done fine, but have lost a few varieties in the heat of the summer. Now I try to move my potted semps into light shade in the middle of summer and they do well, but don't get as large for me as they did up in NY.

I have a dry spot in the yard which faces south, and nothing there seems to survive the summer heat. Not even weeds.

So I've decided to put a rock garden in. Planning to plant Sempervivums, Sedums, and various species of "Ice Plant".

Should I put additional sand and gravel down? Can succulents still take root and spread on a gravel mulch?

In my experience, yes. My sedums regularly go crawling out of their soil to the gravel drive close by. Ice plant also loves those conditions. If your soil is solid clay i'd definitely amend it some first to greatly increase your drainage and friability. Vole bloc/permatill is a great idea- the succulents will like the drainage, and it doesn't break down like so many soil amendments. You can mix it into the soil and use it as a mulch too. Unlike gravel, it's porous. Clay isn't very hospitable to anything when it's dry and packed.

Sempervivums usually occur in the wild in very rocky cold areas - like mountains. Your spot sounds a bit too hot to me. I would stick with some of the sedums (there are plenty that seem to like shade around here, but there are millions of them available so try a few and see what happens), ice plants, portulaca and small mounding grasses like Blue Fescue.

Trianglejohn, about half of my "dry spot" is actually shaded by the house all afternoon.

So I'm thinking about sticking semps & a few other shade lovers (like orostachys) there, while sedums & ice plants would go in the sunnier spot.

Tamelask, do voles like semps?

Because I'm surrounded by woods, and have voles pretty bad. Fortunately they've left most of my perennials alone, but they destroyed the hostas and tiarella (pulled the whole plant underground).

I don't know about voles, but squirrels are my bigest problem with semps.

I've not really noticed the voles bothering the sedums (i grow alot more sedums and iceplants than semps). Certainly not in the rockier areas. Squirrels do have some sort of weird attraction to semps- i've noticed it some, and a friend of mine has had a real problem with them poaching (and i presume eating) her semps. I think i'd make a habit of sprinkling hot pepper around them every so often so they don't get tempted to nibble. It sounds like you have a nice setup where you'll be able to site a good range of things. Take pix when you get it all planted! There's a great sedum/succulent site out there (can't recall the url- but nancedar knows), and they have wonderful pix of freeform trough gardens and the like. Might give you some combo ideas.

Where to begin is http://www.hartmannsplantcompany.com/ OR sedumphotos.net

Identify what you have (I was shocked by how many plants look the same but that they do not have the same behavior nor growing patterns. A good source is: http://www.sedumphotos.net/main.phpreally

sedumphotos.net was the site i was referring to, nan! Thanks much for posting!

I grow semps. To protect my 2.000 plants I use net. See my sempervivum blog http://sempervivum.sosblog.com

The Smith and Hawken catalogue has a great planter for semps. Planted, it appears like a strawberry pot with plants on alternating levels. There's a base(with wheels) and then 4 layers with 4 planting areas and the topmost layer has a deeper wider planting area for a larger specimen.
They show one all planted with semps and similars. I'm going to mail order a couple because they're not expensive.