Eastern hemlock

Eastern hemlock: how do you recognise it?

Habit

Broadly conical tree with horizontal to slightly drooping branches and a nodding tip. Slow-growing; after many years it reaches 15–20 m tall and up to 10 m wide.

Needles

Flat, 1–2 cm long, dark green with two white bands underneath, arranged in two rows along the shoots.

Cones

Small and egg-shaped, 1.5–2.5 cm, hanging from the shoot tips; green at first, later brown.

Bark

Red-brown and deeply furrowed on older trees.

Roots

Shallow and finely branched: sensitive to drought and soil compaction.

Plants: April–May and September–October · Pruning: June and August

Why grow it?

• One of the few conifers that grow well in partial and full shade.
• It takes clipping and makes a fine, dark green hedge that looks softer than most other hedging conifers.
• Green all year: a calm backdrop for flowering shrubs and perennials.
• A dense hedge or tree gives birds shelter and nesting sites all year round.
• Dwarf forms suit a rock garden, a shady border or a large pot.

Eastern hemlock: where does it grow best?

• Partial or full shade; full sun only if the soil always stays moist.
• Humus-rich, moist sandy or loamy soil, acid to neutral. It does not like chalky soil.
• Moist to wet, but without standing water. Drought and drying winds turn the needles brown.
• A sheltered spot with cool, humid air is ideal, for example in the lee of larger trees.
• As a tree it will eventually need 8–10 m of space. For a hedge, plant 50–60 cm apart.

Light

Partial shade and shade

Soil type

Sand or loam

Acidity

Acid or neutral

Moisture

Normal or wet

Size

20 m tall, 10 m wide

Hardiness

Hardy (to -35 °C)

Goes well with

• Rhododendron: Likes the same acid, moist soil and partial shade.
• Hydrangea: White or blue flower heads stand out beautifully against the dark needles.
• Ferns: Fresh underplanting for a shady, moist corner.
• Japanese maple: Fine, colourful leaves and autumn colour next to the evergreen conifer.
• Hosta: Large leaves as a contrast to the fine needles.

Eastern hemlock: when and how to plant it?

Plant in April–May and September–October.

1. Plant in April–May or in September–October, when the soil is neither too cold nor too dry.
2. Dig a generous hole and mix the soil you dug out with leaf mould.
3. Set the plant at the same depth as it was in the pot or root ball and firm the soil well.
4. For a hedge, stretch a string line and plant in a single row, 50–60 cm apart.
5. Water thoroughly straight away and regularly during the first year, also in a dry autumn.
6. Spread a mulch of leaf mould, bark or needle litter around the base.

Care

Watering

Weekly in dry spells during the first year. Older trees also need water in dry summers, because the roots are shallow.

Feeding

In April some leaf mould or an organic feed for acid-loving plants. No more feeding after July.

Mulching

Keep the soil cool with a permanent mulch and simply leave fallen needles where they lie.

Hedge trimming

Trim a hedge twice a year, in June and at the end of August.

Shelter

In the first year, protect a young plant in an exposed spot from drying east winds, for example with a windbreak.

Tip: Looking for an evergreen hedge for shade that looks softer than yew? Choose hemlock in moist, lime-free soil. Mulch every spring: the shallow roots like a cool soil.

Eastern hemlock: when to prune it?

Pruning months: June and August.

When: A freely growing tree needs no pruning. Trim a hedge in June and again at the end of August.

How:

• Trim the hedge slightly narrower at the top than at the base, so the lower branches also get light.
• Cut within the green, needled part and not back into bare old wood: it regrows poorly from there.
• On a young tree, leave the nodding leader alone: it straightens up by itself and forms the new top.
• Remove dead and damaged branches at any time of year.

Caution: Do not trim on hot, sunny days, as freshly cut needles scorch easily. Do not prune later than early September, so new growth can harden before winter.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Cuttings

In August–September take semi-ripe cuttings of 10 cm with a heel and root them in a cold frame or under plastic. It is slow: allow several months.

Seed

Sow in autumn in a pot left outdoors, so the seed gets the winter cold. Seedlings grow very slowly and cultivars do not come true from seed.

Eastern hemlock: how does it get through the winter?

Hardy to −35 °C.

• Very hardy, to about −35 °C: cold is no problem in Belgium.
• Dry east winds and winter sun can brown the needles, especially on young plants. Keep watering in a dry autumn.
• Stand a dwarf form in a pot against a sheltered wall and wrap the pot in hessian, so the root ball does not freeze solid.
• Shake heavy snow off a hedge so the branches do not sag or break.

Diseases and pests

• Brown needles: Caused by drought, drying wind or too much sun. Water in dry spells, mulch and choose a sheltered spot in partial shade.
• Root rot: The plant yellows and dies back in wet, compacted soil. Avoid standing water and plant slightly raised on heavy soil.
• Red spider mite: Finely mottled, dull grey needles and fine webbing in hot, dry weather. Hose the plant down and keep the soil moist.
• Chalky soil: Yellow, pale needles and little growth. Mulch with leaf mould or needle litter; on very chalky soil a yew is a better choice.

Through the year

• January: Shake heavy snow off the hedge.
• March: Apply or top up the mulch.
• April: Plant. Feed lightly.
• May: Plant. New, light green shoots.
• June: First hedge trim, not in bright sun.
• July: Water in dry spells. Watch for spider mite.
• August: Second hedge trim, at the end of August.
• September: Plant. Take semi-ripe cuttings.
• October: Plant. Water in a dry autumn.
• December: Rest. Shake off heavy snow.

Did you know?

• Despite its name, it is not related to poison hemlock, the toxic plant that shares its English name. The name is said to refer to the smell of crushed needles.
• In the eastern United States the species is seriously threatened by an insect introduced from East Asia, the hemlock woolly adelgid.
• The eastern hemlock is the official state tree of Pennsylvania.