HEMLOCK. 



Tsuga canadensis, (Linnaeus) Carriere. 



GENUS DESCRIPTION This genus comprises 8 species in the world, 4 of which are native 

 to North America and 1 to Pennsylvania. Of the 4 species native to North America, 2 are 

 found in the eastern and 2 in the western part. The 2 eastern species are the Carolina Hem- 

 lock (Tsuga caroliniana Engelm.) found only in the mountains from Virginia to Georgia, and 

 the species described below. The Hemlocks are trees of the northern hemisphere, found in 

 North America and Asia, but absent in Europe. The eastern species in particular are slow 

 growers and difficult to transplant. A well known student of forestry has said, "Hemlock trees 

 are like the Indians, they will not stand civilization." 



FORM A large tree usually attaining a height of 60-80 ft. with a diameter of 2-3 ft., but 

 may reach a height of 100 ft. with a diameter of 4 ft. In the open its crown is dense, conic, 

 and high with limbs extending almost to the ground. In dense stands it has a bole, clean from 

 lateral branches for a considerable distance from the ground and with little taper. 



BARK Grayish-brown to reddish-brown, rich in tannin, becoming 4/5 of an inch thick on 

 old trunks and roughened by long fissures separating rather broad ridges which are covered with 

 close scales. Innner bark is cinnamon-red. See Fig. 53. 



TWIGS Slender, rough on account of decurrent projections of bark upon which the leaves 

 rest, at first somewhat hairy and yellowish-brown, later smooth grayish-brown tinged with 

 purple. 



EUDS Alternate, ovate, 1/16 of an inch long, blunt-pointed, reddish-biown, not glossy. 



LEAVES Linear, flat, about i of an inch long, rounded or notched at apex, dark green and 

 shining above, pale green and dull below with a white line on each side of midrib. The leaves 

 persist for about 3 years and are jointed to short, persistent, woody stalks. They are some- 

 what spirally arranged around the twig but appear two-ranked. 



LEAF-SCARS Small, round, raised on decurrent projections of bark. 



FLOWERS Appear about April or May. Staminate and pistillate flowers separate, but 

 usually borne on the same branch. Staminate small, globose, yellow, about i of an inch long. 

 Pistillate oblong and pale green. 



FRUIT A small, short-stalked cone maturing at the end of the first season, about 1 of an 

 inch long, usually persisting during first winter. 



WOOD Non-porous; without resin passages; light, hard, not strong, brittle, coarse-grained 

 not durable, liable to splinter, diflicult to work, light brown with lighter sapwood. Weighs 

 26.42 Ibs. per cubic foot. Used for construction, coarse lumber, and especially for frame 

 work and weather-boarding of buildings, paper pulp, and laths. 



DISTINGUISHING CHARACTERISTICS The Hemlock, also known as Hemlock Spruce and 

 Spruce Pine, can be distinguished by its flat linear needles with two longitudinal white streaks 

 on the lower surface; the needles are jointed to short persistent woody stalks known as sterig- 

 mata and appear two-ranked, but in addition to the two conspicuous lateral rows there is a 

 rather inconspicuous row of small needles on top of the twig extending in the same direction 

 as the twig. The lateral twigs occur rather irregularly along the main branches and diverge 

 from the latter at an angle of usually less than 75. The cones are about I of an inch long, 

 and often persist through one winter. The inner bark is cinnamon-red. 



RANGE Nova Scotia south to Pennsylvania and along the mountains to Alabama, and west 

 to Minnesota. 



DISTRIBUTION IN PENNSYLVANIA Rather commonly distributed in moist situations through- 

 out the mountainous regions of the State. Most common in the central and northern parts. 

 Scattered in local groups, in narrow, cool ravines, and on rocky slopes in the southeastern and 

 southwestern parts. 



HABITAT Usually found in moist locations like northern slopes of rocky ridges, banks of 

 streams, ponds and lakes, swamps, river gorges, and mountain slopes. It prefers a dense forest 

 structure since it is shade loving and not very wind-firm. 



IMPORTANCE OF THE SPECIES This tree yields not only lumber but also bark rich in 

 tannic acid and a volatile oil to which a medicinal value was attached. The inferior wood which 

 it produces coupled with its slow growth and the difficulty with which it is established by 

 planting will tend to decrease its prevalence in our forest structure, especially since more valu- 

 able and more rapid growing species like Pine and Spruce will thrive on the same area. Wher- 

 ever it can be regenerated naturally without sacrificing more valuable species it should be retained 

 in the forest structure. It is one of the most attractive if not the most attractive of our conifer- 

 ous evergreens. 



