Cornus Kousa

From the Missouri Botanical Garden website, read the following about the kousa dogwood. “Cornus kousa, commonly called Kousa dogwood, is a small, deciduous flowering tree or multi-stemmed shrub that typically grows 15-30’ tall, with a vase-shaped habit in the early years but eventually maturing to a more rounded form. Bloom occurs in late spring. The showy parts of the Kousa dogwood “flower” (3-5” across) are the four narrowly pointed petal-like white bracts which surround the center cluster of insignificant, yellowish-green, true flowers. Flowers are followed by berry-like fruits (to 1” diameter) which mature to a pinkish red in summer and persist into fall. Fruits are technically edible, but are usually left for the birds. Oval, pointed leaves (to 4” long) are dark green, but usually turns attractive shades of reddish-purple to scarlet in autumn. Mottled, exfoliating, tan and gray bark on mature trees is attractive in winter.

This matter of fact description does not begin to address the beauty of a kousa dogwood in full and glorious bloom. I doubt I have ever written about them in the 10 years I have been publishing my garden design journal. Primarily as I have never ever seen them so spectacular in flower as they are right now. The kousa dogwood is native to Japan, Korea, China, and Taiwan.  They are rated as hardy and thriving in zone 5 to 8, but my experience suggests they can act a little hostile towards our baking summers, and heavy clay based soil. They seem to favor thin compost rich soil on the acid side that drains in a twinkling of an eye. I do find they perform better than American dogwood (cornus florida) in general.

My theory seems to have some support. This has been the rainiest and coolest spring I can ever remember. We have had many more rainy than dry days. It was 48 degrees this morning, and barely 60 degrees this afternoon. The ground is completely drenched. I make an effort to stay out of the garden, even if it means the foot tall weeds are getting closer to 2 feet tall. The grass is squishy. For the Kousas to put on such a rare show of extravagant bloom says there is definitely something in the air that they like.

The actual flowers are small and insignificant.  All of the show comes from the four stiff bright white bracts that surround the flower. In a stellar year, those thousands of bracts overlap one another to produce a solid sheet of white. Even at maturity, a kousa dogwood is small enough to comfortably place in an urban landscape. Sited with some afternoon shade, a routine source of water and great drainage, all a gardener has to do is wait for that one year when all the stars align for a super bloom.

Should you be one of those people who drives the neighborhood to look at holiday lights, a cruise might be in order.  You can spot them for at least a block away. Out of flower, they have handsome foliage, and even more handsome exfoliating bark when they are older-but the star of the once in a blue moon show are the flowers.

In 2009, a hybrid of Cornus Kousa, and the Pacific coast dogwood, Cornus Nutallii, was introduced from the breeding program at Rutgers University. Again, from the Missouri Botanical Garden website:  the dogwood “Venus”  These four trees planted in the tree lawn at my house are young, but they will grow. Even at a 2″ caliper size, I can spot the flowers from several blocks away.

This hybrid is hardier than either parent.  They thrive in full sun, and grow fast when they are happy. The flowers can easily reach 6″ to 7″ in diameter. We have probably planted better than 100 of them since 2011, with only a few losses. They are a little shy to bloom until they have been in the ground for a year or two, but once they start, they are stop you dead in your tracks gorgeous.

They rival the magnolias for the showiest spring flowering tree.  As with Cornus Kousa, Venus flowers in June, avoiding late spring frosts that so often damage the flowers of magnolias.

A pair of small trees I planted 3 years ago are covered with flowers this year.
This shade garden planted some 4 years ago for my clients features a pair of Venus dogwoods. They are especially happy to have them this year.

Kousa Dogwoods

Cornus kousa, or kousa dogwood, has an impressive list of outstanding characteristics.  Since few properties are large enough for an arboretum, choices have to be made. Trees with year round interest draw my attention.  The kousa dogwood has outstanding exfoliating bark when it is of sufficient age.  Like the sycamore or London plane, a old kousa dogwood will randomly shed bark, revealing new bark of a paler color, from underneath.  As a result, an old trunk is multi-colored, and highly textural.  As much as I like bark, I like the kousa dogwood.  This tree furthermore sets brilliant red fruit in September.  That shiny fire engine red is my idea of fall fireworks.  

Notice I have made no mention of the beautiful white flowers that mature in my yard in June.  In a good year, those flowers may last 3 weeks; my gardening season lasts 7-8 months. I need more interest than what great flowers provide before I am moved to dig the the hole required to plant a tree.  Even my beloved magnolias whose bloom is so fleeting have great bark and branching, and large luscious leaves all season.  A long season of interest-I look for this. My Kousa dogwoods are next to invisible after they bloom.  You can only spot it in this picture, as the leaves are beginning to turn. 

Their green leaves fire up slowly, come the beginning of fall.  The contrast of that red, and that green is riveting.  The shape of the leaves and the pattern of the veins are never more showy than they are in September.  The changing of the guard from the summer foliage to the fall display is an event I follow closely.   

The late September Kousa color is peach; that peach will deepen and mature.  I do not know the science well enough to state the evolution of the color depends on night temperatures that are steadily dropping.  So many times I research my instincts about nature to find out my notions have no basis in fact.  Suffice it to say, the fall color on the kousa changes dramatically over the course of the fall.

I have four kousa dogwoods on the north side of my house.  All four have grown steadily over the past 15 years.  This kousa planted at the front corner of my Romeo and Juliet balcony has grown such that the branches have come up and over the deck; they are at my eye level now.  One branch of that dogwood grows over the driveway far below.  I never notice that branch until the fall colors up the leaves. The garage lights make those leaves glow an orangy red. 

The vibrant red kousa leaves, underpainted and glowing from inside with that early orangy peach color, are the star of my north side garden show for weeks. The fall is all about the evolution of the leaves.  How they grow and photosynthesize over the summer, then turn, how they fade-how they drop-a gorgeous visual lesson in the process that is nature.  The process I am writing about takes the better part of 3 months.  That three month spectacular leaf turn and drop makes a kousa dogwood a tree I would not do without.
There comes that brief time when the red leaves of my dogwoods are just about as intense as the red fruit. That spectacular fall color is one of many reasons why a Kousa dogwood is worth any gardener’s consideration.  I have considered no end of plants for my own garden, and for the gardens of clients.  Decisions get made; trees get planted and take hold.  A good choice matters much. 

A tree is one of nature’s biggest plants.  I think about every tree I plant, and its location, long and hard-given the space it will occupy, and what conditions on the ground it will influence.  I additionally hope any tree I plant will outlive me. That given, I choose which tree for where with great care.  Today I am delighted to have a foursome of Kousa dogwoods thriving in my garden.  Their fall leaves in color delights me.  The summer season has no end of visual delight.  I have three other seasons besides the summer; I have interest in some off-season delight. 

That congested thicket of red-orange kousa leaves peak, thin, and fall.  Those last few dogwood leaves holding on today speak eloquently to the end of the season.  Consider cornus kousa for your garden.  Should you already have one, consider more.  The fall color-enjoy every bit of it.