Tuesday, November 21, 2017

Clematis, Fall-Blooming

Fall-blooming Clematis across top of fence
Sweet Autumn Clematis (Clematis terniflora) differs from most of the species in this family in that it is a fall bloomer of small flowers rather than a spring bloomer of conspicuously large flowers. It is also an aggressively fast climber of arbors, fences and other plants to a height of 10 to 25 feet in a single season. In late August and early September it displays a mass of white flowers suggesting, if anything, a covering of snow.

A couple of months later the plant is visually transformed. The flowers are gone. In their place are the maturing seed clusters. Against a background of green leaves, the seeds appear in starfish-like arrangements of five or six reddish seeds, each attached at one end to a central node, and with a white filament/tail extending from the outer end. En masse, this display could be taken for some under water coral- or anemone-like growth. For whatever reasons, the maturing seeds do not appear to be attractive to birds or other seed eaters, as the display remains intact as time proceeds into fall.

Clematis seed clusters in October.
Click on photos to enlarge
In fact, it is possible that the red coloration is protective. When berries, grapes and fruit first appear on plants the coloration is green. And the sugar content is low. As these seed delivery systems mature, carbohydrates are replaced by sugars and the surface skin takes on a distinct color - think blueberries, cranberries, blackberries. Most of the color is due to the creation of a family of chemical compounds called anthocyanins. These are a fraction of a larger family of compounds called polyphenols - all known to have anti-fungal and anti-bacterial activity. In effect, the dark coloration taken on by maturing fruits and berries (and clematis seeds) is a natural protection against rot.

The second function of coloring up, for grapes and berries called "verison," is a signal to animals that the plants' creations are now ready to be eaten. On the face of it, this feels counterproductive - why go to a season-long effort to create packaging around seeds only to see the end product hijacked by some hungry herbivore? However, the point of being eaten is that  the seeds will pass through the animal's digestive system intact, and because defecation will likely take place distant from the starting point, help distribute seeds to new locations.

Autumn Clematis seed cluster, October
See heads are red, and tails are
beginning to change.
Autumn Clematis seed cluster, November
Seed heads have lost color and
tails have become 'feathery'
This distribution story does not apply to Autumn Clematis. Come late October to early November the clematis seed clusters undergo a gradual transformation. The red fades. The white tail of each seed develops a 'feathery' look. There is no tasty outer fruit to shout "Eat me." Instead, the individual seeds, now too dry to allow bacterial or fungal infection, will in time detach from the core and be borne away on the winds of chance.   

Autumn Clematis is native to Japan; introduced in the United States in the late 1800s. Here, it has no serious insect or disease problems, and in some southern states is being designated as a category II invasive species. Individual plants can get out of hand, for example growing up through a hedge and then completely covering the top with a blanket of white flowers.  Gardeners can control size by cutting a plant to within a couple feet from the ground; the next year it will start its rampant growth all over again. Flowering is on new growth, so there is no loss of a year's flowering after aggressively pruning in the fall.

Pronunciation: Accent on first syllable or second? KLEM-uh-tis or Klem-AH-tis? Various expert sources favor the first, but enough of them acknowledge that the second is valid, too.

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