Hemlocks are evergreen trees belonging to the genus Tsuga, known for their graceful demeanour and year-round allure. With soft, petite needles and cascading branches, hemlocks, particularly the—eastern (Canadian) and western hemlocks, add an aesthetic touch to any space. Ideal for specimen trees, hedges, or living screens, hemlocks attract wildlife, creating habitat-friendly environments. Despite their beauty, hemlocks demand precise conditions for optimal growth, making them akin to the Ferraris of the evergreen world. This comprehensive guide delves into the key facts, varieties, maintenance and intriguing aspects of hemlock toxicity.
Hemlock: Key facts
| Name | Tsuga spp. |
| Common Names | Hemlock Tree |
| Family | Pinaceae |
| Origin | North America, Eastern, and Central parts of Asia |
| Soil | Moist, acidic, well-drained |
| Temperature | Prefers cool, moist temperate regions |
| Sunlight | Partial shade, can tolerate full sun |
| Flowers | Male and female cones; yellowish-white to purple; oblong-cylindric or ovoid globose |
| Leaves | Flattened or angular, 5-35 mm |
| Height | 60 to 70 foot |
| Width | 25 to 35 foot |
| Zones | 3, 4, 5, 6, 7, 8 |
| Lifespan | 800 to 900 years |
Hemlock: Characteristics
Hemlock trees are a part of the Pinaceae family, characterised by their conical crown, horizontal branches, and adaptable growth conditions. Hemlock trees are recognized for their medium to large evergreen conifers. These trees, not to be confused with the poisonous plant sharing their name, offer various uses as ornamental and timber trees. Their physical characteristics include a height range of 33-197 foot, flattened or angular leaves, and a conical crown. With a slow to medium growth rate, these evergreens boast a lifespan ranging from 800 to 900 years.
Hemlock: Types
Hemlock trees come in various types, each with unique characteristics:
Canadian Hemlock (Tsuga canadensis)
- Native to eastern Canada and the Appalachian Mountains.
- Standard height: 40 to 70 foot.
- Dwarf varieties: ‘Gentsch White,’ ‘Moon Frost,’ and weeping form ‘Pendula.’
Western Hemlock (Tsuga heterophylla)
- Native to the western United States and Canada.
- Height: 70 to 130 foot.
- Special variety: ‘Thorsen’s Weeping,’ a dwarf cultivar.
Mountain Hemlock (Tsuga mertensiana)
- Thrives in higher elevations.
- Height: 50 to 90 feet.
- Dwarf variety: ‘Elizabeth,’ remaining 1 foot tall.
Northern Japanese Hemlock (Tsuga diversifolia)
- Native to Japan.
- Height: 35 to 60 foot.
- Resistant to pests, Loowit is a dwarf variety.
Hemlock: How to grow it?
Planting hemlocks requires attention to soil, sunlight, and moisture conditions. Whether from bare root seedlings or transplanting, the process involves ensuring well-drained soil, proper root ball sizing and strategic planting depths.
Planting
- Choose a location with partial to full sun and well-draining, acidic soil.
- For bare-root seedlings, keep the root ball intact or rinse gently and soak overnight.
- Plant high, ensuring the root flare is above soil level.
Transplanting
- Prune roots one year before transplanting to encourage new feeder roots.
- Select a new location, pre-dig a hole, and keep the root ball intact during transportation.
- Set the tree at the same depth in the new hole and add mulch to the planted area.
Root Pruning
- Use a spade to make a circular cut around the tree, stimulating feeder root growth within the future root ball.
How and when to plant Hemlock?
- Plant in early spring for optimal rooting before winter.
- Dig a hole twice as wide as the root ball and water well.
Hemlock: Care Tips
Hemlocks, while low-maintenance, demand specific care for optimal growth. From light and soil requirements to moisture, temperature and pruning, attending to these factors ensures a thriving hemlock.
Light
- Varies among species; prefers partial shade but tolerates full sun.
Soil and Water
- Requires acidic soil (pH 4.0 to 6.0) and regular watering.
- Mulch to retain soil moisture; sensitive to drought.
Temperature and humidity
- Thrives in cool, moist temperate regions; avoids hot and humid conditions.
Fertiliser
- Minimal requirements in rich soil; use slow-release tree fertiliser annually if the soil lacks nutrients.
Pruning
- Lightly shape the tree in late spring if necessary; remove damaged branches promptly.
Hemlock: Benefits and uses
Hemlocks offer diverse advantages:
- Wildlife habitat: Attracts birds and serves as winter cover for animals.
- Timber industry: Hemlock timber is harder and stronger than pine.
- Cultural uses: Bark is used for tanning leather; needles are used for tea and perfume.
- Ornamental value: Cultivars enhance garden aesthetics.
Hemlock: Pest and disease
Hemlocks are generally low-maintenance but can face challenges such as hemlock woolly adelgid, mites, scales, and root rot. Regular inspections and timely treatments are essential for maintaining tree health.
Hemlock: Toxicity
Contrary to misconceptions, hemlock trees are not toxic. It’s crucial to differentiate it from herbaceous perennials like poison hemlock, which are unrelated and pose toxicity risks. With its flat and blunt needles, the hemlock tree remains a safe and non-toxic addition to landscapes.
FAQs
How do you identify a hemlock tree?
Look for flat, blunt needles with smooth, shiny upper sides and two parallel white stripes underneath.
Where do hemlocks grow best?
Plant hemlocks in partial to full sun, well-draining acidic soil, and locations protected from drying winds.
Can hemlocks tolerate drought?
No, hemlocks are sensitive to drought; regular watering, especially in the first two years, is crucial.
What is the primary threat to hemlocks?
The hemlock woolly adelgid poses a significant threat, requiring regular inspections and necessary treatment.
Are there dwarf varieties of hemlock?
Yes, several dwarf cultivars, such as Gentsch White, Moon Frost, and Thorsen’s Weeping, offer compact alternatives.
How long does a hemlock tree survive?
Usually, hemlock trees have a lifespan ranging from 800-900 years. I
Is hemlock poisonous?
No, the hemlock tree (Tsuga spp.) is not toxic. Poisonous varieties are herbaceous perennials like poison hemlock, unrelated to the tree.
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