skybird, I remember you said last year you were trying to get rid of the heinous "rock mulch." I am still cursing myself for following expert advice and putting it in my perennial gardens. I got rid of most of it last year and replaced it with cedar mulch--best move I ever made and my plants agree. Rock mulch is wonderful for those areas that you don't plan to dig or plant in (around seedlings lining the driveway, etc.) It does have its functional uses, but not near my gardens, thank you.

I'm in zone 4a and mine come back every year - this year they look like crap because I've been neglecting to water :O I have rocks rocks rocks and more rocks LOL, on top of something like 18" of clay/silty soil (beneath my scant soil is dense river rocks - it's nasty trying to dig anything deep in our old river bed area). i have only two kinds right now, but next year when my dry stream bed is ready I'll buy some of those two square foot mixed sedum "tiles" they sell at Home Depot :) like this: they had them for $20 and I'm kicking myself for not picking a couple up The Angelina I just chucked in here last year because my dry stream bed wasn't ready yet and I didn't want them to die...barely any soil on top of gravel backfill from the sidewalk, under a spruce. The could use more than just rainfall and they're full of debris from the tree, so they don't look very happy right now. That was just six 2" plugs last year. and these (Kamtschaticum?) are well established, 3 years or so. This is an old bed, maybe a foot of soil and lots of old mulch and tree debris. They're sprawling across the rocks these are cuttings I accidentally broke off from the main area and literally just poked in with my fingers, and pressed soil and mulch down around them: I have some spurium (dragons blood) and a few others to put in... I got a raggedly looking "patio basket" on sale at Rona for $5 and it had 3 or 4 kinds of sedum in it. I also got a few different sempervivums on sale as well. All cold hardy.

Sedum sarmentosum - hardy in zone 4 http://www.itsnotworkitsgardening.com/2013/06/stringy.html My mother called this Gold Moss and had it all over her rock garden. This plant spreads quite well and needs very little soil. In fact, Mom thought it spread a little too well. It even grew in the spaces between the stacked rocks. It's a perennial that comes back even after a hard winter. It flowers in the spring.

Though this isn't a great photo, to my eye, his plant looks virtually identical in growth pattern and color to my Dianthus 'Greystone' though the foliage is a bit smaller. It has the same low, dense tufts of blue-gray foliage and relatively even edge from its outward expansion. I've had similar Dianthus plants with finer foliage but the same color and growth pattern. Here Armeria tends to grow in more distinct buns IME and the individual tufts of leaves are more distinct and a bit more green, though still in gray-green end of the scale. I've grown several types of both in at least two gardens and this is just my observations from what I see here in the NE.