WE ALL KNOW that the best rock gardens are not just tiny perennials and rocks. To be interesting year around, dwarf evergreens and miniature shrubs are needed to add structure to the garden. With their dense, compact growth, I like to think of them as living transitions between boulders and alpines. In the mountains, the landscape above the timberline is dotted with gnarly evergreens and crawling or mounded shrubs. Re-creating this scene takes some effort because commonly offered conifers and shrubs are grown for large landscapes, not for detail-oriented, small-scale rock gardens. Cute in a pot, they quickly outgrow their place and shade out or smother their diminutive neighbors. Dwarf conifers are a subject of their own and are often described while other dwarf shrubs tend to be overlooked. Not often are the delights of miniature rhododendrons revealed, though they bloom beautifully and are in scale with flowering alpines.