Eastern Hemlocks have been grown as excellent screens and shade trees due to their general tolerance of pests and diseases. They feature soft, tiny foliage with minuscule light-brown cones. T. canadensis also grow slowly and typically with only one trunk, making them ideal for bonsai. However, the emergence of hemlock woolly agelids (Adelges tsugae, abbreviated HAW) have led to striking decreases in hemlock populations, drastically reducing hemlock populations across North America. However, these hemlocks can survive in colder zones than these terrible pests, offering a refuge in northern areas.
Tsuga canadensis (Eastern Hemlock, Canadian Hemlock)
Hardiness Zones: 3-7, dislike temperatures above 35 degrees Celsius (95 degrees Fahrenheit)
Height: 12-21 meters (40-70 feet) tall usually, recorded to reach 53 meters (175 feet) tall
Diameter: 7.5-10.5 meters (25-35 feet) tall
Growth Rate: slow
Age: reaches maturity around 300 years old, may persist to 800 years old
Root System: minimal surface roots, typically shallow, deeper when water availability permits
Subspecies: ‘Bennett’ (globular dwarf), ‘Sargentii’ (dwarf, to 4 meters (12 feet) tall by 6 meters (20 feet) wide at 80 years old), ‘White Gentsch’ (round, flat dwarf)
Tolerates: Black Walnut (Juglans genus) toxins (Juglones), herbivores (deer), dense/heavy shade (in southern, warmer areas), most pests
Problems (major): Sun-scald, drought, dry soils, and high temperatures (above 95 degrees Fahrenheit) in warmer climates in sunny areas. Hemlock woolly adelgid
(HAW) are extremely minuscule insects that have killed an enormous amount of hemlock trees, especially in warmer climates where the HAW can overwinter.
Problems (minor): needle blight, cankers, rusts, root rot (in overly wet soils), bagworms, borers, leaf miners, saw flies, spider mites
Poisonous: No, Poison Hemlock plants belong to an entirely different family.
Soil requirements: prefers moderately moist, acidic, well-drained light/sandy or moderate/loamy soils
Air requirements: intolerant of poor air quality (urban pollution)
Watering requirement: moderate to high (higher in southern regions)
Sun requirement: full sun (northernmost range) to part-shade to full shade (warmest southern climates)
Needles: lacy, soft, dark green (light green when newly formed), appear in flat sprays, to 1 centimeter (0.5 inches) long, 2 white lines/bands (stomata) on the underside
Cones (male): yellow, tiny, globular
Cones (female): small, light green when newly formed, light brown at maturity, to 2 centimeters (0.8 inches) long
Seeds: tiny, light brown
Bark: grayish-brown when young, maturing to less smooth and reddish-brown
Form: wide, conical
Seeds require stratification: yes
Monoecious or Dioecious: monoecious
Eastern Hemlocks have a pyramidal growth form. The needles of this particular conifer are the smallest in its genus. The foliage and branching patterns are adept at handling copious amounts of snowfall.
Canadian Hemlocks, in areas not affected by HAW, are excellent screen and shade trees. These tend to perform in the cooler part of their range, as the HAW are not as cold hardy as these hemlocks. These are occasionally used as bonsai because of their tiny foliage.
All of the images provided were taken by me. They may be used for educational/informational purposes only, provided that this article/online journal is appropriately cited first.