When making lists such as this, there has always been, and will always be, a discussion as to what constitutes a shrub as opposed to a tree. I have no intention of adding to this debate, but will simply keep to some useful, lower-growing woody plants that offer four-season beauty in the garden.
When assessing which plants meet these criteria, the multitude of conifers and other evergreens immediately come to mind. It becomes more challenging, however, when considering deciduous candidates. Many have lovely flowers, colourful berries and even fascinating winter silhouettes but, unfortunately, rather mundane leaves throughout the summer months.
Here, therefore, are a few suggestions to jump-start your own investigations. Keep in mind, though, that beauty (or interest) lies in the eye of the beholder. Consider, too, the size of your area, your soil conditions and your garden's overall environment.
Gardeners wishing to grow plants other than the usual suspects may have to hunt around specialist nurseries (or, if you're really keen, grow from seed). In the long run it's well worth the effort.
Shrubs for sunny rock gardens
In a sunny rock garden with well-drained, not-too-rich soil, I recommend evergreen bearberry (Arctostaphylos uva-ursi, Zone 1), which has a creeping habit of 90 centimetres or more. It's five to 15 centimetres tall. Cultivars such as ‘Vancouver Jade' (30 centimetres tall by 100 centimetres wide), developed at the University of British Columbia, are probably hardy to Zone 4. If the site is partly shady, consider rose daphne, with its mass of sweetly scented blooms. Rockspray cotoneaster is another good choice. Its creamy white flowers in spring, shiny green leaves in summer and plentiful red berries in fall and winter are very attractive. After leaf drop, the fanned-out, herringbone branches add additional winter interest, especially when grown against a large rock or other plain, solid backgrounds.
It's hard to imagine a rock garden of any size devoid of silky leaf woodwaxen. The most popular variety these days, and justly so, is ‘Vancouver Gold', also developed at UBC. It's a lovely low, spreading evergreen shrub producing a mass of golden flowers in late spring. I've found it advantageous to protect this shrub from the western or southwestern spring winds, so I usually tuck mine behind a large rock. It's easy to propagate from cuttings if you keep them misted (i.e., moist).
Peaty, well-drained soil
In the peaty, well-drained soil that's ideal for Erica, Calluna and rhododendrons, I would also grow Andromeda ‘Blue Ice', a dwarf bog rosemary with outstanding powdery blue foliage year-round. It carries umbels of white-tinged, pink flowers in spring. Another small-scale candidate is slow-growing cliff green. Where light shade is available, I recommend evergreen Japanese pieris. The Pieris japonica cultivars ‘Cavatine', ‘Dorothy Wyckoff', ‘Forest Flame', ‘Mountain Fire' and ‘Valley Fire' all reach a height and spread of roughly 1.25 metres. These shrubs, with their clusters of white, bell-shaped flowers, provide a nice contrast for rhododendrons and other ericaceous plants, but they need careful siting away from cold winds and scorching sun to survive in Zone 5b. ‘Brouwer's Beauty' may be slightly hardier, but should still be similarly treated.
Photos, from top: Spring heath, Ernst Kucklich; Rhododendron in spring and winter, Ernst Kucklich (spring) and Joan de Grey (winter).