Today, all rules can be broken, and although I have many alpine troughs planted with true alpines, I also plant some with other plants, such as this trough of South African Gasteria species ( and one Aloe species). One could argue that these are still alpine or alpine-esque plants, since many grow on top of mountains in South Africa, but regardless of what anyone says, a trough can be planted with anything. A shrub, a small evergreen, even bulbs if it doesn't freeze. This trough is just a simple concrete one purchased at a garden center, and I planted it with many seedling Gasteria species which a friend has bred. Now, in the summer, it is blooming, and it is easy to care for since Gasteria are succulent, and can survive with little water.
Most any succulent grows well in troughs, and contemporary ones like this slate cube, displays a smart mix of Echeveria sp. and other succulents which look terrific in the full sun conditions of our terrace. It also looks like a crispy salad to Lydia, our new puppy, who has become a reign of terror for all succulents in pots this summer.