Cornus Kousa: Outstanding tree and why you need to reconsider planting it
Consider starting with the native Cornus Florida
Without a doubt the most impressive understory tree in our woodland garden is the Cornus Kousa, but I urge gardeners thinking about planting one to reconsider.
It’s not that the Cornus Kousa isn’t spectacular in flower – it is.
It’s not that the fruit that follows is not impressive and a favourite of our local squirrels and chipmunks because they are.
And, it’s not because these elegant, horizontally branched trees are susceptible to disease and deer predation, because they are almost totally free of disease and other garden pests.
Sounds like the perfect tree, right?
Just one big problem – and it’s a problem many of our most visually pleasing and impressive plants and trees have in common, – it’s not native to North America. Its home is in China and other parts of Asia where, I am sure, it is a favourite food source for their native insects, caterpillars, birds and mammals. In fact, you will often find the plant referred to as the Chinese Dogwood.
Our mature Cornus Kousa in full bloom among the ferns. To the left is a Cornus Florida and the small mound in the centre is a variagated Cornus Mas.
The difference is, their local fauna has grown up and adapted to Cornus Kousa and, as a result, are able to use it as a host plant, a food source and provider of habitat.
With all that said, I have two massive Cornus Kousa trees growing in my yard and absolutely treasure them for their mid-summer display of large, cream-coloured flowers that bloom for months during the summer followed by bright red eatable raspberry fruit that eventually get picked off by red squirrels, grey squirrels and chipmunks.
Be sure to read my detailed look at the Six best Dogwoods in my garden.
More of my posts on Dogwoods
For more information on Dogwoods, please check out my other posts listed here:
Dogwoods: Find the perfect one for your yard
Flowering Dogwood: Queen of the Woodland garden
Bunchberry: The ideal native ground cover
This graphic was produced by Justin Lewis and shows the benefits of planting a native dogwood over a non-native.
So, when I say “reconsider” planting one of these small, but impressive trees, what I really mean is before you plant one, make sure you’ve already planted the equally beautiful (some would say more beautiful) native Cornus Florida or Flowering Dogwood.
In fact, the combination of the Cornus Florida and Cornus Kousa growing alongside one another is an impressive site that creates an outstanding blooming period beginning in May with the native dogwood and continuing into late summer with the Kousa dogwood.
Cornus Kousa in full bloom among the ferns.
In our woodland garden there is also a couple of early blooming native Redbuds growing with the two dogwoods creating a a truly dramatic spring show. A multi-stemmed serviceberry is also beginning to make its presence known in the grouping that grows out of our massive fern garden. Be sure to check out the full story on our fern garden.
Our native Flowering Dogwood blooms about a month earlier than the Kousa and on mostly bare branches which make its bloom even more impressive than the Kousa dogwoods. It is also a host plant to a huge variety of insect larvae and caterpillars as well as a favourite haunt of native birds including the elusive bluebird and the cardinal, just to name two stalwarts.
Be sure to check out my full story on the Flowering Dogwood (cornus Florida).
An example of Cornus Kousa fruit (raspberry like) ripening on the tree.
But back to the Cornus Kousa. And why it is such an outstanding landscape plant either used as a specimen or as an understory tree in the woodland or shade garden.
Cornus Kousa has more of an upright habit, making it a little better suited to smaller or more narrow properties.
Close-up of ripening bright red fruit of the Cornus Kousa.
How to grow Cornus Kousa
The Cornus Kousa grows in zones 4 through 9 and likes a rich, well-drained acidic soil and adequate precipitation to look its best.
Chinese Dogwood is a multi-stemmed deciduous tree with an expected growth of between 25-40 feet (8-12 m) tall at maturity, with a spread of about 25 feet. If left natural, it has a low canopy with a typical clearance of about 3 feet from the ground. It grows at a medium rate, and under ideal growing conditions should live for 40 or more years.
Cornus Kousa’s best features
Cornus Kousa’s most prized feature is its horizontally-tiered branches along with its showy clusters of white flowers (actually bracts, the flowers are contained inside the four bracts) held upright atop the branches in late spring through summer depending on its location in the garden. The Cornus Kousa flowers are more pointed than the native Flowering dogwoods more rounded ones.
It has bluish-green deciduous foliage that turns an outstanding brick red in fall. It does best in full sun in cooler climates to partial shade and will not tolerate standing water. Cornus Kousa is also resistant to the dogwood anthracnose disease making it popular in areas that experience outbreaks of the fungus disease that can be fatal to the trees.
How to prune Cornus Kousa
This low-maintenance tree should be pruned sparingly after flowering to maintain its horizontal branching that looks at home in any Japanese-style garden as well as a traditional woodland. It’s also a good idea to mulch around the extensive root zone to protect the tree’s roots from drying out.
Hybrids offer best of both
The popularity of the Cornus trees have prompted Rutgers University to create a host of hybrids between Cornus Kousa and Cornus Florida, selected for their disease resistance and flower appearance.
Some of the popular cultivars include: Beni Fuji with deep red-pink bracts, Elizabeth Lustgarten and Lustgarden Weeping notable for its smaller size and weeping habit, Gold Star a slower growing tree with a broad gold band on its leaves and reddish stems, Satomi with deep pink bracts and leaves that turn purple to deep red in fall.