The Graceful Hemlock

Hemlock – foreground – parched fall background

This summer because of the heat and drought I have spent a lot of time across the brook in my woods because it is always so cool in there. As parched as the land is elsewhere, in the forest I can still find the occasional mushroom, examine various mosses and lichens (the latter remind me that the air quality is excellent), peer into rich green bogs searching for new plants, or sit by the feeder brook that still trickles down the mountain.

author standing in front of same tree a few weeks ago

The deep shade I seek is due in part to the graceful Hemlocks that tower over my head. When this land was last cut about 40 years ago the Hemlocks were spared because they weren’t considered to be a valuable ‘resource.’ They are the biggest trees on my land and I love them. Even today although clear cutting removes all trees including the Hemlock this tree is not considered to be of much value in comparison to other trees like pine or spruce.

Hemlocks are the most shade tolerant species of all trees. They can persist in the understory as a suppressed tree for up to 400 years. In places where they are still allowed to grow it is not uncommon to see a one inch diameter Hemlock sapling that is 60 to 100 years old.

Although they grow slowly they can reach two to four feet in diameter and 100 feet or more in height. Our Eastern Hemlocks can take 250 to 300 years to reach maturity and can live more than 800 years. The oldest Eastern Hemlock is almost 1000 years old (988 years).

Hemlocks have to have certain conditions to regenerate. Although they produce their little cones frequently – every two or three years – seed viability is low. In order for the seeds to germinate (many are destroyed by insects) temperature and moisture conditions have to be just right. Temperatures have to be around 44 – 64 degrees for a few weeks and adequate moisture has to be present for seeds to germinate. 

Hemlocks like to grow in pure stands but they also closely associate themselves with white pine, spruce and fir, yellow birch, red oak, and red maple. A tree loving friend of mine would add Northern White cedar to the mix and I would too. Hemlocks are often found along lower slopes and along streams. I have a lot of young Hemlocks growing down by my brook. Hemlock roots help prevent erosion along river and stream banks, and their dense canopies provide cool shade keeping the air around them full of moisture.

Tannaries were a major industry in New England during the 1800’s. High in tannins, Hemlock bark was prized for treating animal hides because tannins are a preservative. The bark gives leather a dark red-brown color. Millions of Hemlocks were felled and stripped of their bark. The rest of the tree was left to rot, a disgusting waste from my point of view but so typical of the American lumber industry…Economy ‘trumps’ Life every time. The tanning industry declined in the early 1900’s giving Hemlocks a chance to reestablish stands before these trees were logged again. 

Hemlock presently represents about 20 – 25 percent of the softwood timber industry in the northeast. 

Today the lumber is used for timber frames, to build barns and is a popular choice for bridges on logging roads and trails, but isn’t considered ‘valuable’ like pine or spruce.

Wildlife benefit from Hemlock stands. Dense stands reduce snow depth and help moderate temperatures helping deer and rabbits conserve energy during the cold winter months. Many birds and other mammals use Hemlock stands for breeding and protection. Owls, in particular like Hemlock and here I have Barred owls living in my woods along with grouse, and turkey. Porcupines feed on Hemlock bark and branches. When walking through the woods if you see an area with lots of Hemlock branches on the ground at once you know a porcupine is feeding in the area. Our collective nemesis, the Red squirrel, eats Hemlock cones.

Unfortunately several insects attack Hemlocks. The woolly adelgid (the worst) is a non native insect that feeds on hemlock twigs and creates a loss of tree needles (it can also be found on Norfolk Island pines – so beware of white “snowy” patches on these or other live trees that are sold as indoor Christmas trees). This insect reduces the ability of the tree to produce new growth, and an untreated infestation can kill a tree in 2 – 12 years. Unfortunately this pest has reached Maine’s coastal areas and is spreading inland. 

Over one third of the Eastern hemlock’s native range has been infested with this bug. The larvae spread rapidly through the air on their own or by wind and birds. Even though a quarantine has been established for Maine, New Hampshire and Vermont, the infestation is spreading. The 2013 revision of the quarantine rule is one reason why:

“Hemlock chips with top material, and uncomposted bark with top material from quarantined areas may be imported into non-quarantined areas in the State of Maine provided that said material is shipped only to sites within Maine that are preapproved by the Maine Forest Service, Department of Agriculture, Conservation & Forestry. Such sites must have a compliance agreement with the Maine Forest Service”.


 Here is the kind of legal crazymaking loophole that catches my hair on fire. If you use bark as mulch, which many gardeners do you are probably responsible for the spread of this devastating disease.

In the northern portion of the Hemlock’s range, the color of the Hemlocks infested by this invasive insect will typically change from a healthy, dark green to a sickly, grayish-green color after just a few years, and death typically occurs four to ten years after an initial infestation.  Any trees that do manage to survive the direct effects of this assault are usually weakened to the point where they may die from secondary causes.

Hemlock scale and Hemlock borers are additional threats. Brown flecks on the needles reveal the presence of the scale. Should you note a collection of orange chips surrounding a Hemlock tree (due to woodpeckers drilling into the cambium for insects) then the Hemlock has probably been infested by the borers.

Once the insects are established on Hemlocks there is little to be done. The Maine Forest service has released a couple of non native insects from Japan to deal with infestations, creating of course, another problem in its wake. With the future of these trees so uncertain I take refuge in the present and spend a lot of time appreciating these beautiful woodland trees. One day, they may not be around to enjoy.

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