Pumice you say. Unless pumice is considerable cheaper in Cali than it is elsewhere, it would preclude many from ever growing sedums due to expense. I would think CA 5 or CA 6 construction grade sands would be far more affordable and provide more than adequate drainage in even the densest clay soils. CA 5 is an industry standard, 3/8" and finer mix of sand and gravel, CA 6 is 1/4" and finer. These should be readily available through sand pits or sources for construction materials such as brick yards. I can see where soft sedums may need a little more attention to soil amendments than the hardy varieties. I don't believe that resorting to pumice is the only solution.
I admire the hardy sedums for their tenacity and toughness to grow well, and thrive under a variety of conditions.
This is Sedum Sarmentosum growing in a redwood window box planter on my front porch. It gets good light, and maybe if the winds are right gets some rain. Occasionally I'll dump a gallon of water in it when it looks thirsty. The soil was left over from when my wife was trying to grow Petunias, nothing special, no sand, no gravel, no pumice and this planter has been growing like this for close to 15 years. All of my Sarmentosum originated from some scrappy looking starts a kindly neighbor gave me.
Same source as above, this is a redwood specimen planter that the specimens never did well in, (too many mail carriers knocking into them as they trudged up my front steps. Again the soil is noting special, 50% composted leaf litter, 50% of the black river bottom that makes up the bulk of the natural soil in my yard. This is one of two planters, growing like this. These get more exposure to full, day long sun and whatever rain nature provides.
Beneath those is this upended log my wife uses for one of her solar garden lanterns. Snippets of Sarmentosum fall down, root up wherever, the log, the cypress mulch, cracks in the sidewalk, out from under the debris that accumulates around the planters. I'm leery of planting this in the ground for fear of it becoming invasive.
Another upended log, this one a tad more intentional as my wife actually transplanted some of the volunteers here. No soil, no amendments, just the decaying end of the log. Full sun all day, nature provides the water.
The last of the Sarmentosum, I promise. 3 of the many baskets my wife loves to fill. She loves petunias and after they die off, she feels compelled to reuse them. Leftover Petunia soil, scraps of volunteers tossed on top. Full sun, no special soil, when it rains, they get wet. BTW she has 8 more of these type baskets going up each side of our front steps.
All of the Sarmentosum is semi evergreen, dying back to the planter soil surface every winter, coming back like gangbusters every spring.
Petrosedum rupestre subsp. rupestre 'Blue Spruce' aka Sedum 'Blue Spruce' I had this growing as a ground cover, border plant for a number of years. When we redid the bed we really had no place we needed this. I did keep a some of it as I do really like it and figured if I really needed quantity again I could grow out in flat trays. The first photo is the original pot from that time. It pretty much was ignored, rain, snow, sun, blazing heat, sub zero cold and crappy soil, it survived it all. Finally this past spring the pot was perhaps half full of soil and it was starting to look raggedy. I dumped the root ball out, added some fresh soil underneath and put it back in. I did molly coddle it a little bit by top dressing with #2 poultry grit.
The next two photos are more of the same. The wife had gotten some of her beloved Petunias in wire hanging baskets with coco fiber liners. Once empty she tossed in some errant volunteers from the other hanging basket. No special care, no rooting up under special conditions. She literally tossed the cuttings on the soil, in full sun and they took. More than 10 years in those baskets and they were also looking raggedy, the birds had removed most of the coco fiber and not much soil remained. I literally scraped aside the mulch in 2 different beds and plopped the contents of the baskets in place. These are a couple months after planting, they were in pretty rough shape as evidenced by the network of old stolons.
Phedimus sichotensis akd Sedum sichotense. I have a nursery flat of this I'm growing out and took some cuttings a couple months back. I was curious about different soil pH and the effect it might have on growth, color etc. Left photo, soil is grit, sand, potting mix and sifted pine bark, pH is right at neutral 7. These cuttings were stuck in the soil, planter was placed in full sun on top of an upended black walnut log we use as planter stands. No nursery time to root the cuttings, I did water a little more frequently but no molly coddling at all. They look pretty happy and if you look closely you can see all the tender new shoots coming up from below.
Right photo was an alkaline soil mix. No bark, more grit, a little potting soil and "rock base" which is essentially old mason mortar that the bags got wet and the mortared hardened. They crush this up, rebag it for use as a base for cultured "rock" retaining walls as a leveler. Same full sun, water etc.. Still looks healthy but not as vigorous with this more alkaline soil mix. Although it may have as much to do with the much shallower container.
This is a S. spurius (Phedimus spurius)NOID growing in the same mix, location as the right hand photo above.
Some cuttings from a neighbor of a red S. spurius NOID. Sandy, humusy mix. I stuck these in a small grower's pot and set on the corner of my potting bench. Full sun from day one, dunked from time to time in my rain water catch buckets. No molly coddling.
Hylotelephium spectabile 'Herbstfreude' aka Sedum 'Autumn Joy' These were some bare root leftovers from a big box, pop up garden center, that my wife picked up. (Yes she will drag home stray kittens too.) I wouldn't have given 2 cents for them. She was just giggly as a school girl about them. I left her to it. She potted them up in 1 gallon grower's pots with regular potting mix. They're looking pretty good to me. I will have to maybe get more involved with them come spring, cutting them back, rooting the cuttings, heck I may even put them in the ground. I have a neighbor down the block that has this growing as a border all along the sidewalks on her property. I know they are growing just in our black river bottom soil. They are evergreen all winter and bloom profusely late summer every year.
@MsNorris. The point I'm trying to make is, you do what works for your garden. If you soils seems like it may be a bit too mucky, you mind work in some sand, and possibly pea gravel to help with drainage. If you've perused the sedums at Young's you've seen they are not that expensive to at least try some and see how well they do. Some of the softer ones you may have to provide a bit more care, as opposed to my "get tough or die" with the hardier ones.
Good luck with your garden. Post pics as it comes along.
to the NGA forums MsNorris. 
