The measure of acidity or alkalinity of any substance, including soil, is the pH scale that ranges from 0 to 14. Ideally, soil should be neutral, or 7 on the scale, which would mean that it was equally acid and alkaline. If you have alkaline soil, which is anything above 7, your choices are to adjust the pH of your soil or choose plants that are compatible with an alkaline environment. The latter is simpler and less expensive.
One of the most attractive shrubs for alkaline soil is Carolina rose, Rosa Carolina, which grows to a height of about 3 feet and spreads 6 to 12 feet in width. Because of its thick, spreading nature, it is useful as filler between other plants in large beds. Carolina rose, or pasture rose as it is sometimes called, is characterised by old-fashioned, single-type roses that are soft pink and fragrant. Though Carolina rose is not evergreen, attractive red rose hips brighten the winter garden after the flowers are gone. Plant in moist, well-drained locations when possible; however, this rose is surprisingly tolerant of less than optimal conditions and will grow in both wet and dry soils. It is hardy in zones 5 through 8. Like most roses, this one likes full sun but will adjust to partial shade.
Evergreen common boxwood, Buxus sempervirens, continues to be a staple in garden centres and nurseries because it is so versatile and useful in the garden. Pruned to a formal or fanciful shape or left to assume its natural rounded profile, boxwood presents a solid, almost structural appearance due to its dense profusion of stems and leaves. Boxwood is often thought of as a small shrub because many boxwood hybrids are indeed small, but left to its own inclinations, this variety will reach a height and width of 15 to 20 feet. It makes an almost impenetrable hedge that can be sheared to maintain a precise shape or size, and it assures as much privacy as a fence. Boxwood will grow in full sun to partial shade and is hardy in zones 5 through 8.
Famous for its heady fragrance that fills the garden and wafts through any open window, Syringa vulgaris, or common lilac, has been a strong favourite among gardeners for generations. The flowers, which are large, upright spikes, appear in late spring and may be pink, white, lavender, purple or even bluish. Lilac is a large shrub that can reach a height of 8 to 15 feet and a width almost equal to its height. It is useful as a hedge, tall border or specimen and is hardy in zones 3 through 7. Lilac performs best in full sun with moist, well-drained soil. Many cultivars are available, and since common lilac is prone to certain diseases, choosing one of the more resistant types will decrease maintenance on the shrub.