The Hemlock Tree

This was a definite first for the majority of us on the instructors’ weekend, an escapee making its home in the Derbyshire woods.

There are eight to ten species within the genus, depending upon which authority subscribed. Four are North American species, and a further four to six in eastern Asia. This makes it particularly difficult to define which species we had.

The common name – hemlock tree is derived from a perceived similarity in the smell of its crushed foliage to that of the unrelated plant poison hemlock Conium maculatum.  Tsuga species are not poisonous. So, when Nicola offered some Hemlock tea to try, she wasn’t trying to kill us!!

If you are ever in our Derbyshire woods, you will have to be prepared for a fairly long trek, as this particular tree was situated at the entrance to a small quarried area on the Eastern boundary. The location certainly matched the environment where this species would thrive: relatively moist, cool temperate areas with high rainfall, cool summers, and little or no water stress; more tolerant of heavy shade than other conifers.

Tsuga trees are medium-sized to large evergreen trees, ranging from 10–60 m (33–197 ft) tall.

Adam Logan had recently returned from an extended over winter trip to Canada, and it was his experience working with the Hemlock trees that was able to give us the initial identification, based upon the look and smell.

The leaves are flattened to slightly angular and range from 5–35 mm long and 1–3 mm broad. They are borne singly and are arranged spirally on the stem; the leaf bases are twisted so the leaves lie flat either side of the stem or more rarely radially. Towards the base, the leaves narrow abruptly to a petiole (stalk) set on a forward-angled pulvinus (a joint-like thickening at the base of the leaf that facilitates growth-independent movement). The petiole is twisted at the base so it is almost parallel with the stem. The leaf apex is either notched, rounded, or acute. The undersides have two white stomatal bands separated by an elevated midvein. The upper surface of the leaves lack stomata. They have one resin canal that is present beneath the single vascular bundle.

In the field, it is often very difficult to identify the exact species, without specialist reference material, especially when there are so many potentials. With the reference material available, it was confidently identified as a Hemlock tree, with a leaning towards the Eastern Hemlock. The bark of the hemlock is used in tanning leather. The needles of the hemlock tree are sometimes used to make a tea and perfume. The wood is used for general construction and crates. Untreated, the wood is not durable if exposed to the elements. As a fuel, it is low in value. The wood is also a source of pulp for paper manufacturing.