Dogwood (Cornus spp.)

Posted by shane - March 3, 2011 - A-Z Plant Maintenance, Shrubs - No Comments

Dogwood is truly one of the most reliable garden shrubs for Alberta.  Native to parkland forest understories, it is also one of the only plants that will grow well in shady areas of the yard.  I consider dogwoods a four season ornamental, with interesting flowers in the spring, nice berries in the summer, great fall colour, and beautiful bright stems to provide winter interest.

There are many cultivars of dogwood available at nurseries.  Personally, I prefer the species, Cornus stolonifera, as it is most hardy.  That being said, all of those rated zone 3 or less should work fine, provided they are planted and maintained properly.

Red-Osier Dogwood (Cornus stolonifera)

Red-Osier Dogwood near Sylvan Lake, AB. Shane LePage photo.

This species is my favourite dogwood.  One of its best assets is that it will grow well in shadier sites, which is common in mature Alberta neighbourhoods that are clustered with shade-throwing spruce trees.  In Red Deer,  I often recommend dogwood or cedar for less-than-ideal light conditions.

Lately, I’ve taken an interest in Niwaki, the japanese art of pruning, and am experimenting with some mature dogwood plants in Red Deer.  Given enough space, dogwoods need little pruning.  But if it’s a dramatic display of bright new stems, or if the shrubs are included in a dense, mixed planting, where spacing is not desired, pruning is a definite must.  Also, old, overgrown dogwoods tend to benefit from reinvigoration, every few years.

Pruning to Encourage Decorative Stems

This technique is most suitable once the specimen has an established root system.  I don’t recommend the following technique on newly planted shrubs.  In late winter to early spring, cut back all dogwood stems to about 4″ above ground level to form a tidy “stool.”  Don’t be alarmed if the plant doesn’t respond with new growth early in the growing season.  In the Red Deer area, I find that it takes well into July to get a nice looking, regenerated shrub.  It is worth the wait.  The new foliage seems to glow with vigour and rich, healthy colour.  This process can be done annually, but I find that it’s a nice idea to rotate this type of hard pruning between various dogwoods in the garden, alternating years, or perhaps pruning this way every three years, or until they start to encroach on neighbouring plants.  All dogwood cultivars can be pruned similarly.  Yellow-twig dogwood is particularly suited to this technique.

Reinvigoration of Overgrown Specimens

Most often, I am called in to look at messy, overgrown specimens dominating some corner of a back yard.  I prefer to prune dogwood in the dormant season, late fall to early spring, so I can see what I’m working with.  I remove as much deadwood as is necessary for the specimen, but usually dead stems down to 1/8″ diameter or smaller.  The shrub should look neat and clean, for starters.  Next, I remove conflicting stems; those that intertwine, saving those that best contribute to the overall form of the shrub.  I like all remaining stems to have a bit of space, especially if it will be several years before the shrub is pruned again.  Lastly, I reduce the height and width, only as much as necessary, and using reduction-type pruning cuts, in order to balance and contain the shrub.  The end result is a tidy, attractive, balanced, and healthy looking specimen.

Irrigation & Fertilization

As with most woody plants, dogwoods prefer a moist, well-drained soil, with a wood-chip mulch cover.  Planted and maintained in this manner, these plants should not require irrigation or fertilization.  I would consider watering only after prolonged hot, dry weather in summer.

Pests

Dogwood is insect and disease resistant.  I have, however, encountered some problems, namely aphids and oystershell scale.  Aphids are messy and unattractive, buy they aren’t that serious.  Hose them off of try some relatively non-toxic spray, such as an insecticidal soap.  Other contact insecticides work well, such as Malathion, but please use caution when using chemicals.  Oystershell scale is more serious, and must be controlled when the scale “crawlers” are active, in early to mid-June.  Use any contact insecticide.  In my practice, I have used Orthene with excellent success and it offers systemic control as well.  Timing is everything.

(c) Shane LePage, Wild Rose Garden & Tree Service, Red Deer, AB, (403) 755-5899