Highlights

 

Liz gives BIG HEMI a hug on a previous BIG HEMI wellness check visit.

Read on if you want more info on the Eastern Hemlock:

Eastern hemlock is one of our most beautiful evergreens. It is usually found growing in shady ravines, along brooks and on the north side of narrow valleys. Our most shade tolerant native conifer it thrives in areas the sun barely reaches. 

Although you won’t see any of this size in the woods of Southeastern Massachusetts, hemlocks can grow to a height of over 150 feet with trunks over 6 feet in diameter. They grow very slowly and do not produce seed cones until at least 20 years old. Some do not reach maturity and bear cones until over 100 years old. Large specimens can be over 1,000 years old. 

Unfortunately our hemlocks are under extreme stress, many dying, from attacks by the Asian hemlock woolly adelgid. The invasive woolly adelgid is a very serious threat to the continued survival of the hemlock and those species that depend on the hemlock. You’ll find more on the woolly adelgid in the article below.

Eastern hemlock have short, flat needles, a half inch to an inch long, dark green above with two narrow white lines running the length of the needle’s underside. The needles are attached to their twig by a slender stalk.

Tiny flowers are produced in spring with inch long cones ripening in the fall and releasing seed during the winter. Many winter birds and small forest rodents depend on hemlock seeds as a winter food source.

The eastern hemlock grows best in damp, acidic soil from extreme southern Ontario and Quebec east to Nova Scotia. From Nova Scotia south along the Atlantic coast to New Jersey and then inland following the Appalachian Mountains to extreme northern Georgia and Alabama. To the west, the hemlock range extends south from southern Ontario to eastern Minnesota, Wisconsin, Michigan and then down the western side of the Appalachians.

On the northern edge of their range whitetail deer depend on eastern hemlock for food and shelter. Dense stands of hemlock slow the accumulation of winter snow beneath them. When heavy snows, frigid temperatures and strong winds buffet our northern forests small family groups of deer gather at these hemlock stands, called “deer yards,” for shelter, feeding and bedding. Young, dense hemlocks also provide food and shelter for snowshoe hare and various species of forest voles and mice.

A fortifying tea can be made from hemlock needles. And, no, this is not the “hemlock” Socrates drank. Socrates’ death-sentence drink was concocted from poison hemlock, Conium maculatum, an herbaceous plant, not a tree. 

Not that long ago hemlock bark was rendered for tannin, which was widely used for tanning leather prior to the development of various chemical methods which require less labor and are more economically advantageous.

There are numerous insect species that feed on hemlock. Only two of these are capable of killing their host. One of these is the previously mentioned alien hemlock woolly adelgid and the other is the native hemlock borer which preys on weakened hemlocks often killing woolly adelgid compromised trees.

Old eastern hemlocks and hemlock stumps and logs occasionally nurture an interesting and much sought after medicinal fungus. The hemlock varnish shelf polypore, Ganoderma tsugae, is very closely related to the highly valued Asian “miracle” mushroom reishi or ling chi/lingzhi, Ganoderma lucidum.

Both mushroom species contain triterpenes, polysaccharides and sterols and both can be made into a “tea” reportedly containing immunotherapeutic properties, anti-tumor inhibitors and enhancers for anti-viral and antibacterial activity.

One can easily see the eastern hemlock is a species we do not want to lose. Unfortunately, like the American elm, American chestnut and various other native species, that have been extirpated from vast areas of their natural range by introduced insects and diseases, the future is not bright for this grand American tree.

The hemlock eating woolly adelgid is a fairly recent arrival to our New England forests first making an appearance around 1990. They are a Japanese species first arriving on the west coast in 1924 and have been expanding their range east and north ever since.

The present range of this adelgid is from Virginia, North Carolina and east Tennessee north up the Appalachian Mountains and the coast to southern Maine.

As with almost all alien invasive species they found a bountiful food supply and few predators. In the woolly adelgid’s native Japan there are species of native insects that have evolved to prey on wooly adelgids keeping their numbers in check and doing only minor damage to Japan’s native hemlocks.

Wooly adelgids are supposed to have difficulty surviving temperatures below 20 degrees Fahrenheit, but a check of Southeastern Massachusetts Bioreserve hemlocks in February, when the temperature was in the teens, showed many adelgid infested trees.

Wooly adelgid abundance also comes from the fact that they not only reproduce sexually, but also reproduce by parthenogenesis. Adelgids produce two generations a year. One generation overwinters on the hemlock. In this overwintering generation the adelgids are called “sistens.” Sistens are wingless and reproduce parthenogenetically. In the second, spring generation the adults are “progrediens.” There are two forms of progrediens, another wingless form that remains on the hemlock and a form that has wings that flies off in search of a different host tree, a species of spruce not found in North American forests. The winged progrediens are all viviparous (producing living young instead of eggs) females which give birth to both males and females which mate and the females then lay fertilized eggs. However, these guys do not survive to reproduce and add to the adelgid population in our area because, as mentioned, we don't have the required host spruce necessary for their survival.

The eggs of the hemlock staying progrediens hatch into nymphs which are so tiny and light that the wind easily disperses many of them throughout the forest. Those fortunate enough to land on a hemlock crawl to the underside of a hemlock needle and insert a pointed mouthpart, stylet, into the base of the needle. There they remain feeding on phloem, the food conducting tissue that supplies the hemlock with the nutrients it needs for survival. The nymphs pass through four growth stages on their way to becoming adults.

A hemlock heavily infested with wooly adelgids slowly turns grey and dies. Biologists have been studying a number of beetles and fungal diseases that keep the wooly adelgid population under control in Japan. Whether they will be effective predators of this invasive insect species on this continent has not yet been definitively determined.

----------------------------

 

 ACTIVITY ALERT - Hike to visit BIG HEMI and upcoming walks in May and June

Great to see that BIG HEMI is still standing proudly, despite a missing top, other storm damage and the ravages from native and introduced insects and diseases. Increasing greenbrier growth, between the trail and tree, prevented all but one intrepid BIG HEMI visitor ...orange spot in photo ...from making a close approach. Hope she gave BIG HEMI a hug.