Friday, June 14, 2013

Flowering Dogwoods Are Beautiful And Versatile Trees.

Cornus florida in full flower  ©2013BDG
I just love Dogwoods.  They are one of the most versatile ornamental trees and they provide that valued four-season interest.  I rate it slightly behind my favorite, Stewartia psuedocamellia, but it performs well in all five of the criteria I use in rating ornamental trees:  Habit, flower, bark, fall color and winter interest.

Pink Cornus florida flowers  ©2013BDG
There are many different types of plants in the Cornus genus, including a wonderful ground cover called Cornus canadensis and a number of shrubs.  In New England, most of the planted trees are either the native Cornus florida, the Korean Dogwood (Cornus kousa) or the Rutgers Hybrids, which are a cross between florida and kousa.  There is also Cornus mas, Cornus alternifolia, Cornus controversa, Cornus chinensis and several others, but the most significant in our landscape are florida, kousa and the hybrids.

These three major species flower in white and pink colors with a broad variation in each color range.  The whites range from pure white(f. 'Cherokee Princess', k 'Milky Way') to cream (k 'National') to greenish-white(k 'Ticknor's Choice').  On the pink side they range from delicate pink(k 'Stellar Pink') to deep red-pink (f 'Cherokee Chief).

Pink Cornus florida in bloom
before leaves emerge ©2013BDG
Arguably, the best floral display by any tree is the native Cornus florida, that is the first Dogwood to flower in late April or early May.  What makes this display so amazing is that it comes before the tree has leafed out and the flowers can literally cover the whole tree.  Of all the Dogwoods, it has the most interesting horizontal, tiered form and with minimal pruning can be a stunning specimen that looks as interesting in winter as during the summer.  Unfortunately this species suffers from a disease called anthracnose that without care will shorten their life.

In its native habitat, it is considered an understory tree in woodlands, so it prefers some shade and will suffer in full sun or dry conditions. It has a red berry that forms in summer from the flower and can be distinctive in the fall

Cornus kousa in flowers.  Notice the linear appearance
of flowers on the branches  ©2013BDG
The Korean or Kousa Dogwood is the last to flower  in June and some cultivars are known for carrying their flowers through much of the summer.  'Summer Star' is one of the longer flowering cultivars.  The Kousa dogwood is different in that it flowers about a month later than florida, when the leaves have already emerged.  The flower displays can be just as impressive and are offset by the green leaves.

Close-up of dense kousa flowers  ©2013BDG
A distinct look of the Kousa in flower is the long line of flowers along the branches.  There appears to be a flowing, linear display of flowers as you can see in the image.  The Korean is much more sun tolerant and is better suited in a hot, sunny location as opposed to the florida species.  Its habit is more upright than the florida species, but still develops nice horizontal branching.  

A very cool aspect of the Korean Dogwood is the round red berry that develops in the late summer.  They persist on the tree into winter and can be quite decorative in the fall.

Years ago someone told me that fruit, inside the outer skin, is edible, so I tried it.  Cardboard is edible too but I choose not to eat it often.

In comparison, I feel that the native florida tends to be broader and more structural, while the kousa is a little more upright with a traditional tree shape.

Cornus x 'Constellation' hybrid  ©2013BDG
The Rutgers hybrids were developed as a result of crossing florida and kousa.  These hybrids flower in between its two parents and the flowers emerge just before the leaves and finish after the leaves have emerged.  It is a prolific flowering tree like its florida parent but doesn't have some of the cultural problems.  Generally it lacks the graceful horizontal form in youth but the branches do settle with age, yet it is no substitute for the beautiful form of the florida species.

'Constellation', Rutgers Hybrid flower  ©2013BDG
All of these wonderful species have beautiful and variable red leaves in the fall and an interesting checkered and peeling bark.

There is a dogwood for just about any space in the garden and I feel it is one of the best and hardest working trees you can find.  Because they are relatively easy to propagate and are moderate growers, Dogwoods are not a very expensive tree.

Here in New England we get to see these trees flower from April to July and if you have the space for multiple specimens you can have trees that provide year round interest and flower over a four month period.

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