Western hemlock

Western hemlock: how do you recognise it?

Habit

Slim, conical conifer up to 30 m tall and 8–10 m wide, with drooping branches and a nodding leader.

Needles

Flat, 0.5–2 cm long and of unequal length on the same twig; dark green above, with two white stripes beneath.

Cones

Small, hanging cones 2–2.5 cm long, ripening in autumn.

Bark

Dark brown and deeply furrowed on older trees.

Roots

Shallow and wide-spreading: a free-standing tree can blow over in a gale.

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

Why grow it?

• Evergreen and graceful: soft, fine needles and a nodding leader.
• Tolerates a lot of shade, more than most other conifers.
• Grows fast and makes a dense, green hedge when clipped.
• The dense branches give birds shelter all year round.
• An impressive specimen in a large garden or park.

Western hemlock: where does it grow best?

• Partial shade or shade is ideal; in sun only if the soil stays moist and the air is not too dry.
• Sand or loam, acid to neutral and rich in humus. Not on chalky or very dry soil.
• Normal to wet soil; it wants a cool, moist site, but not standing water.
• Sheltered from strong, dry wind, especially cold east wind in winter.
• Specimen: 6–8 m of space. Hedge: 2–3 plants per metre, so 40–50 cm apart.

Light

Sun, partial shade and shade

Soil type

Sand or loam

Acidity

Acid or neutral

Moisture

Normal or wet

Size

30 m tall, 10 m wide

Hardiness

Hardy (to -25 °C)

Goes well with

• Rhododendron: Likes the same acid, humus-rich soil and partial shade.
• Ferns: Fresh, green underplanting in the shade.
• Hosta: Big leaves in the shade beneath the branches.
• Japanese maple: Coloured foliage in the light shade next to the dark needles.

Western hemlock: when and how to plant it?

Plant in April–May and September–October.

1. Plant in April–May or September–October, when the soil is moist and not frozen.
2. Dig a hole twice as wide as the root ball but no deeper, and loosen the sides.
3. Mix a little leaf mould or acid compost into the excavated soil, but no fresh manure.
4. Set the plant at the same depth as in its pot or root ball and firm the soil lightly around it.
5. Water in generously straight away, even if it is raining.
6. Spread a 5–8 cm layer of bark or leaf mould around the base to keep the roots cool and moist.

Care

Water

In the first year water every week in dry spells, spring included. A mature tree wants plenty of water in dry summers; it copes poorly with swings.

Feeding

In April or May an organic fertiliser for conifers or a layer of acid compost.

Mulching

A mulch of bark or leaf mould keeps the roots cool; renew it every spring.

Hedge clipping

Clip a hedge 1–2 times a year (see pruning). A specimen is left in its natural shape.

Air humidity

It likes a cool, humid climate. Do not plant it against a warm wall or on a dry, paved spot.

Tip: Put it in a sheltered, moist spot and give it a thick mulch: it copes poorly with dry wind and dry air. For a hedge choose young plants, which establish better than big ones.

Western hemlock: when to prune it?

Pruning months: June and August.

When: A specimen needs no pruning. Clip a hedge in June and, if you like, again in late August.

How:

• Clip a hedge slightly tapered: wider at the base than at the top, so light also reaches the lower branches.
• Cut only into young, green growth; never cut deep into old, bare wood, as it rarely shoots again there.
• On a specimen keep one leader and remove double leaders.
• Remove dead or damaged branches, even outside the pruning season.

Caution: Never cut the top off a specimen: it loses its typical nodding leader. Do not clip in frost or in bright sun.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Seed

Collect the cones in autumn, let them dry open and store the seed cold. Sow in spring in acid, moist potting compost in partial shade. Seedlings grow slowly at first.

Cuttings

Cuttings root slowly and seldom succeed at home; nurseries mainly use them for hedging plants.

Western hemlock: how does it get through the winter?

Hardy to −25 °C.

• Hardy to about −25 °C: suitable in Belgium without protection.
• Dry, cold east wind and winter sun can scorch the needles. Water in long frost-free dry spells and put young plants in a sheltered spot.
• A thick layer of mulch in November protects the roots of young trees.
• Shake the branches in wet, heavy snow so they do not break.

Diseases and pests

• Brown needles: Needles turning brown in spring or after a hot summer: drought, winter sun or cold wind. Water, mulch and choose a sheltered spot.
• Root rot: Yellowing needles and a declining tree on wet, heavy soil. Improve drainage or plant higher; an affected tree is hard to save.
• Spider mites: Fine webbing and dull, pale needles in warm, dry spells. Spray the tree regularly with water and keep the soil moist.
• Windthrow: With its shallow roots a tall, free-standing tree can blow over. Plant it sheltered or in a group.

Through the year

• March: Prepare the planting spot. Do not let fresh root balls dry out.
• April: Plant. Apply mulch.
• May: Plant. Give an organic feed.
• June: First clip of the hedge. Water in dry weather.
• July: Water in dry weather. Check for spider mites.
• August: Clip the hedge again (late in the month).
• September: Plant.
• October: Plant. Renew the mulch.
• November: Mulch young trees.
• December: Rest. Shake the branches in wet snow.

Did you know?

• The species name heterophylla means ‘with different leaves’: the needles on one twig are of unequal length.
• It is the state tree of Washington in the United States.
• In its native forests the seed often germinates on the rotting wood of fallen trees.