Here's another view of a Rocky Mountain alpine tundra meadow. This is a pretty lush portion with lots of vegetation, and tall too! At higher altitudes yet the vegetation is lower and sparser. These are great places for botanizing in season, you know those two weeks of balmy weather above freezing. The mid-summer temperature this day was 38 F (3 C) and in exposed places the wind chill made it feel much colder. But it was sunny, and down close to the ground it wasn't so severe and as you can see quite a number of plants are in flower; lots of composites, pinks, legumes, some cinquefoils and sedums, and some grasses & sedges. Of course lots of these species would look great in your rock garden; it's their natural habitat, and while they are certainly cold hardy when covered in snow, they would absolutely fry in the heat of our central midwest summers. Unfortunately some alpine species, particularly European ones, are being marketed as hardy perennials, and while true in the sense of cold, they won't survive summers in our climate, so it's another example of rather unethical marketing.