Garden Notes

oak twig
The oak twig points to the white bodies of the hemlock wooly adelgid (Adelges tsugae) on the hemlock twig's underside. Photo by Susan Safford

Eclipses, hemlocks, poultry, and more

By Abigail Higgins - March 15, 2007

Island snowdrops have shown inspiring fortitude this year. Since before Christmas they have been in many stages of the act of flowering: emerging, almost in bloom, or actually blooming, across the Vineyard. This week the wait is over, with green and white legions completing the act of opening up for the business of supplying those early foraging honeybees and other nectar lovers.

Riding home on the Islander the Saturday night of the lunar eclipse, the final trip aboard her for me, was a notable occasion, not to be forgotten. By the time we were mid-Sound and I had made my way out on deck, the moon was restored and waves and Island were bathed in cold bright moonlight. I was returning from attending the annual conference of the Ecological Landscaping Association, a worthy organization that attempts to educate its members about ways to lessen negative environmental impacts arising from our work as gardeners and landscapers. Earlier in the evening on our way to Woods Hole, the moon's looming disk had been a dark brick red. It was awesome, but had I been a person of a pre-industrial era, I surely would have wondered if it was some sort of omen.

In a way, it was. All eclipses are rated on the Danjon scale, which compares the overall darkness of lunar eclipses, L=0 being the darkest and L=4 having the most visibility. Here is Wikipedia on the appearance of lunar eclipses: "The Moon does not completely disappear as it passes through the umbra because of the refraction of sunlight by the Earth's atmosphere into the shadow cone; if the Earth had no atmosphere, the Moon would be completely dark during an eclipse. The red coloring arises because of the scattering of sunlight in the Earth's atmosphere. Sunlight reaching the Moon must pass through a long and dense layer of the Earth's atmosphere, where it is scattered by dust particles. Shorter wavelengths are more likely to be scattered by the small particles, and so by the time the light has passed through the atmosphere, the longer wavelengths dominate. This resulting light we perceive as red....

"The amount of refracted light depends on the amount of clouds or dust in the atmosphere; this also controls how much light is scattered. In general, the dustier the atmosphere, the more that other wavelengths of light will be removed (compared to red light), leaving the resulting light a deeper red color." The March 3, eclipse has a Danjon rating of between L=3 and L=4. This rating means that there was a great deal of color evident in the moon disk and, therefore, a great deal of dust and particles in Earth's atmosphere.

As chance would have it, one of the conference talks I attended, by Dennis Souto of the USDA's Forest Service, was on the subject of insect tree threats, including hemlock wooly adelgid. A minute, aphid-like insect that sucks plant juices and covers itself with a waxy, white protective coating, hemlock wooly adelgid has been a beneficiary of climate warming (the dust, gases, and particles in our atmosphere), spreading out our way from farther south. Every warm winter has seen its reach spread further into New England.

Once home I decided to check my own modest stand of hemlock (half Canadian hemlock, Tsuga canadensis, and half Carolina hemlock, T. caroliniana) and holy cow, there they were! Every year for years I have checked: nothing. But now a thin sprinkling of white dots along the hemlock fronds reveals that my trees have finally been attacked, and the temperature just 12 degrees Fahrenheit!

I don't mean to suggest that the color of the eclipsing moon could be seen to foretell the adelgids on the hemlocks; but there is a connection between climate change and new and baffling pests on our trees and crops. It is a tough time to be a tree, needing pure air and water vapor for your stomates to breathe in and pure rainfall to bathe your leaves, needles, branches and bark.

For the great stands of North American hemlock, a magically beautiful evergreen and great timber resource downwind from the power plants and industrial remnants of the American heartland, the future is grim. The USDA has worked to build stocks of two small predaceous lady beetles, which seem to hold promise as a control of the hemlock wooly adelgid where they have been released; but many years must pass before this strategy becomes effective and many trees of great stature face a poor outlook in the meantime.

I plan to cover the hemlocks as well as I can with insecticidal soap and possibly dormant oil spray. Fortunately, I can keep an eye on them and the infestation so far seems light compared to Mr. Souto's images at the ELA talk. Avoidance of drought stress through mulching and adequate rainfall/water become important as summer progresses.

I am looking forward to the next round table discussion at Agricultural Hall. The last one, on seeds and seeding, was a very pleasant evening with lively panelists and audience. We hope for more of the same Wednesday, March 21, from 7 to 9 pm with the Martha's Vineyard Agricultural Society's roundtable discussion on backyard poultry. Panelists include MVAS trustee Jim Athearn of Morning Glory Farm; home farmer, gardener and Vineyard Gazette columnist Lynn Irons; organic poultry producer Mitchell Posin of the Allen Farm; and Katherine Long and Tom Vogl of Up Island Eggs. All aspects of backyard poultry, egg production, and meat birds will be up for discussion and the audience, it is hoped, will be ready to participate. Refreshments will be served and the evening is free and open to the public.

On a connected but jarring note: with the eggs really coming on now, this is one of the best times to make and store gift plum puddings for the 2007 holidays. Put away now to cure, well sealed in cling wrap at the back of the fridge or in the "beer box" down cellar, the puddings develop complex ethereal flavors by December.

From Polly Hill Arboretum comes notice of the plant conservation training program on Saturday, April 7, from 9:30 am to 4 pm in cooperation with the New England Wild Flower Society. This program puts the skills of amateur botanists to work relocating and collecting data on populations of rare plants throughout New England. This is an excellent opportunity to learn more about the flora of Martha's Vineyard and New England. Pre-application is necessary. For information call Ailene Kane of NEWFS at 508-877-7603 x 3204, or go to the NEWFS web site at www.newfs.org to download an application. You may also contact PHA, at 508-693-9426.