Care-free shrubs: red-osier dogwood

Also called red-twig dogwood, this species grows into a many-stemmed, shrubby clump that welcomes spring with small, yellowish white flowers and oval green leaves. These guidelines will show you how to properly grow red-osier dogwood shrubs.

When the sap rises in late winter, the stems of red-osier dogwood turn from purplish brown to vibrant red, lending much-appreciated colour to the landscape.  White berries emerge in summer, which birds relish and harvest before the leaves drop in fall.

Although an individual plant is attractive, a mass planting makes a dramatic, unusual statement when the stems colour up in cold weather. You can set this plant off to best advantage by growing it against a backdrop of evergreen trees or shrubs, or underplanting it with an evergreen ground cover, such as ivy. It is just the right size for combining with clumps of ornamental grasses. Because it spreads by suckers, or shoots growing up from the roots, red-osier dogwood is also a good choice for controlling erosion on hillsides or stream banks.

For real winter drama, mix the species with cultivars that have different stem colours. 'Flaviramea' has golden-yellow stems in winter, while those of 'Kelseyi' are yellow-green tipped in red. All varieties will tolerate shade, but the stem colour is much improved when grown in sun. In many varieties, cold temperatures bring out the brightest colours. 'Cardinal', for example, shows striking cherry-red stems when grown where winters are cold but is yellow-orange where mild.

To vary the look during the growing season, you can also mix in a variety with colourful foliage. The green leaves of 'White Gold' have broad, white margins.

Several other dogwoods also produce colourful stems in winter.

• Tartarian dogwood (Cornus alba) is similar to red-osier dogwood, though a little slower to spread.
• The 'Sibirica' and 'Bloodgood' cultivars have red stems that rival those of true red-osiers. This species is also hardy to Zone 2.
• Other good choices include the 'Corallina' cultivar of the pagoda dogwood (C. alternifolia) and bloodtwig dogwood (C. sanguinea), especially 'Winter Beauty', which has yellow-orange stems tipped in red. Both are hardy to Zone 4.

• Set out plants in spring so they will be well rooted by winter.
• Keep the soil slightly moist and mulch with five centimetres (two inches) of compost or other organic mulch.
• Each spring sprinkle a light application of balanced timed-release fertilizer to encourage vigorous new growth and more spectacular stem colour the following winter.
• While red-osiers can reach 2.5 to three metres (eight to 10 feet) in height, pruning techniques that stimulate colourful new stems will also control plant size.
• In late winter, either cut the oldest one-third of the stems to ground level annually or cut all of them back to the ground every three years.
• The first method will result in tall, symmetrical shrubs, while the second approach is best when growing red-osier dogwood as a hedge.

Potential problems include powdery mildew and other fungal leaf diseases, but they usually cause only cosmetic damage. Should severe problems develop, prune plants back hard in winter and destroy the prunings. Newer varieties often show improved disease resistance. Planting in an airy site and keeping irrigation water off leaves discourages fungal diseases.