I don't really draw a line to my sedum placement or volume. Aside from being tossed into my many flower beds as ground cover, I also have a number of special sedum planters, including an old chair, the bottom half and flue of a terracotta chiminea, my window boxes, and a little metal pan that sits on an old rocking horse I have on my deck.
I love them. Some bloom, others don't, but the riot of texture and tones floats my boat. Some thrive, others struggle, but in the end, in early summer, they're dense, lush and colourful. And so low maintenance to boot.
This winter took its toll; not only on my sedum collection, but on some of the containers. My lush sedum chair has been reduced to a stubbly, sad looking mess, and a number of my tiny hens & chicks have died, but some still cling on, and fight to gain footing again.
They are great plants. They make perfect window-box plants because they don't mind being dried out sometimes. There are varieties that will hang down over the side, varieties that bloom, that look like dense flowers with reddish and purple tones. They propagate so easily, a cutting, a pinch turns into a huge mound of living matter. I truly love these plants. :)
I recommend these plants for the not-so-great gardener like me. I have visions of a cottage garden, which has been a challenge with my sandy, organic-poor soil, but my sedum gardens have never failed me. You can buy some in early spring, and by summer, they'll be bursting over the edge of your containers. If you forget to water them once in a while, they won't wilt and die. And when you look at how lush and green they are, and your containers are dripping in them, you'll feel very accomplished indeed. Go to your local nursery and give them a whirl. Once you start, you won't stop. You'll become a sedum addict and you will find yourself pinching pieces off of plants in your friends' and public gardens.