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.

Wednesday, November 15, 2017

Winter Moths - Act Now to Save Your Trees

December 3rd update: Male winter moths are seen flying after sunset. Our birch tree is trapping far more males than females. This indicates that after four years of tree banding our local infestation of females is lessened, but the pheromones the trapped females release are attracting males from a larger distance. In effect, we are doing the neighborhood a favor. It is not necessary to band every tree every year.

November 15, 2017: Winter moths, previously written up (Nov 2014 and May 2016) as an invasive species, will soon be starting to emerge from their pupal state, triggered by the first few frosts. If you start seeing large numbers of moths flying around in the evening, it’s time. And if you intend to protect your trees, act now. Garden supply stores, including Russell's Garden Center (Wayland), carry Tree Tanglefoot in 15-ounce containers. One container should be enough for a few trees. The product can also be ordered on line in that size or five-pound pails.

White birch tree with plastic wrap covered with Tree Tanglefoot. Females
get stuck at the bottom edge. Males, attracted to their pheromones, get
stuck higher up. Click on photo to enlarge.
The procedure for using this sticky stuff is to wrap the trunk of the tree two or three feet off the ground with clinging plastic wrap. Optionally, secure this with a band of duct tape on the top and bottom edges of the plastic wrap (not touching the tree). Then, open a container of the product and use a 1.0 to 1.5 inch wide spatula to smear the stuff on the plastic. Do not apply directly to tree. Wearing disposable plastic gloves while working with this stuff is a good idea, as it is hard to wash off bare hands. The wrap should be left on until late December.

Garden supply stores also sell a roll of a paper product that has the sticky stuff pre-applied. All you have to do is unroll it around the tree trunk. Negatives with this version of the product are that it's expensive, moths may be able to pass under the band if the tree bark has deep fissures, and the sticky band is so narrow that it can become completely filled with moths within days. This means you will have to remove it and repeat the process, else the next wave of females just climbs over the dead bodies of the early ones.    

Female winter moths climbing up a birch tree trunk.
The reason this works is that winter moths have an interesting dimorphism. Males have strong flight muscles, with an ability to pre-warm these muscles through shivering before cold weather flight. In contrast, females have only vestigial wings. Sacrificing flight capacity allows more than fifty percent of their adult body weight to be given over to eggs. Mating is achieved after the females climb up tree trunks and then release scent pheromones into the air. Males fly to them. Both sexes get stuck in the sticky stuff.  

Winter moths, native to northern Europe, reached Canada in the 1930s. The introduction was accidental, the problem monumental.  The "winter" part of the name refers to an evolutionary strategy used to avoid predation. Most insect eaters are active during warmer months. By not emerging until after late November frosts, there perils are avoided. This plague appeared in eastern Massachusetts around 1990 and to date has slowly spread to affect land east of Interstate I-495 and down into Cape Cod, but not farther west. Yet.

Female winter moth, with vestigial wings.
The trees to protect are birch, maple, and any type of fruit trees. Winter moth eggs hatched in early April. The tiny, tiny hatchlings climb inside beginning-to-open leaf and flower buds and nibble from the inside. By early June the full-sized, green, inch-worm-like caterpillars will descend to the ground where they will transform into pupae, not to emerge as adults until next winter.

Help is on the way. Canada successfully introduced parasitic flies and wasps from Europe. Both prey specifically on winter moth caterpillars, with eggs hatching inside, and larvae consuming the caterpillars from the inside out. The U.S. Department of Agriculture has been experimenting with this approach. The net result is a downgrade from traumatic damage to minor damage, with occasional bad years. However, until these bio-controls are introduced locally, best advice is to sticky-band your favorite trees in the fall as being much less expensive than spraying in early spring.