May 24, 2002
Grower's Six Pack:
Flowering Dogwoods

By Lawrence C. Sherk, Sheridan Nurseries Ltd.

Mention dogwoods to most horticulturists in all but the mildest parts of Canada and they will mention Silverleaf Dogwood (Cornus alba 'Elegantissima') and the other cultivars of this species; the Gray Dogwood (Cornus racemosa) or the Red Osier Dogwood (Cornus sericea) and its cultivars. All of these dogwoods are noted for their colourful foliage and/or colourful twigs. All of these have very small flowers born in flat, rather insignificant clusters 2 to 6 cm across. Even what we know as flowering dogwoods have the same small clusters of flowers, but all of their clusters are surrounded by four, very showy, petal-like white or pinkish deciduous bracts that give the appearance of large flowers.

     Two species, Cornus florida and Cornus nuttallii are native to restricted parts of Canada and it is really these areas that generally define that hor¬≠ticultural usefulness because of the lack of hardiness of the exposed flower buds that are fully developed before the onset of winter. Cornus florida (Zones 6 to 9) is commonly called the Flowering Dogwood and reaches its northern limits in the "Carolinian" forest zone of southern Ontario, that is south of a line from Grand Bend to Oakville. It can be found as an understory, small tree and along the edge of woods in acid, sandy soils. The Flowering Dogwood can be used in any of these areas in southern Ontario but care must be taken to be sure that the stock was produced from northern seed sources or is a hardier cultivar such as 'Cloud 9' (Zones 5b to 9). Other selections are noted for their variegated foliage, i.e. 'Cherokee Daybreak' with leaves colourfully variegated with white, green, yellow or their coloured flower bracts, i.e. 'Rubra' or 'Cherokee Chief' with colourful ruby-red bracts. Red fruit follow the flowering of all Flowering Dogwoods in late summer with its brilliant red to burgundy fall colour.

     Fast-forward to British Columbia and one finds the Pacific Dogwood (Cornus nuttallii), a larger tree of 12 to 15 m. This dogwood is also the floral emblem of British Columbia, even though it's hardy only in its native area (Zones 8 to 9), and is not hardy in most of the province. A hybrid of Cornus florida and Cornus nuttallii, 'Eddies White Wonder' is slightly hardier (Zones 7b to 9) and is more widely used where hardy in coastal British Columbia. Sheridan Nurseries did have a specimen survive for many years on a very protected site in Oakville, however the flower's buds never fully survived a winter there.

     The Chinese Flowering Dogwood (Cornus kousa chinensis - Zones 5 to 9) is slightly hardier and later flowering (late June) with larger, more pointed creamy white floral bracts that last for several weeks. Fall foliage colour is also a deep red colour. The selection 'Milky Way' is extremely floriferous with the flowers often totally covering the plants.

     The newest Flowering Dogwood to garner attention is Cornus x 'Satomi' (a hybrid of Cornus kousa and Cornus florida) with large, deep pink floral bracts covering the horizontal branches in mid to late June. Younger plants tend to be somewhat scrawny and open branched, so 200 cm tall trees or larger calibre sizes are more saleable. Fall foliage colour is a deep reddish-purple. Can't grow any of these Flowering Dogwoods because they aren't hardy or you don't have the room? Then consider the native bunchberry (Cornus canadensis) that grows all of 20 cm high on forest floors in deciduous and coniferous woods across much of Quebec and Ontario, right up to Hudson's Bay. No question of hardiness here, but in cultivation, it does require a moist, acid soil with plenty of humus and shade from the hot summer sun. This is a low perennial with herbaceous stems, each topped with its diminutive flower clusters that are surrounded by four pointed floral bracts, 1 to 2 cm long. These are followed by showy, bright red, berry-like drupes, 5 to 8 mm in diameter, in small clusters from July to September. A closely related species, Cornus suecica grows in the eastern Canadian Arctic, the Yukon, northern British Columbia and the Northwest Territories. With the increasing interest in "native" plants, bunchberry is becoming much more widely available, but like almost all native plants, it is very particular about the soil conditions needed for it to be successfully established in a garden.