Japanese cedar

Japanese cedar: how do you recognise it?

Habit

Slender, conical tree with a straight trunk; up to 20 m tall and 8 m wide after many years. Dwarf forms stay rounded and small.

Needles

Awl-shaped, 0.5–1.5 cm, spirally arranged and curving forwards; fresh to dark green, bronze-red in winter on some forms.

Bark

Red-brown and fibrous; it peels away in long, narrow strips.

Cones

Round, 1–2 cm, green at first and later brown, at the shoot tips. The small male cones shed pollen in spring.

Roots

Widely branching in the upper layer of soil; it soon suffers in dry ground.

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

Why grow it?

• Evergreen: structure and colour all year round, even in the depths of winter.
• The fibrous, red-brown bark is lovely close up, especially on older trees.
• Many garden forms: from dwarf buns for a rock garden or pot to a stately specimen tree for a large garden.
• Some forms turn bronze-red in winter and green up again in spring.
• It copes with pruning better than most conifers.

Japanese cedar: where does it grow best?

• Sun or partial shade; young trees appreciate some shade in the hottest part of the day.
• Moist, humus-rich soil: sand or loam, acid to neutral. It grows poorly on chalky soil.
• Moisture matters: a damp spot is no problem, dry and poor soil is.
• Sheltered from cold, drying east winds, which turn the needles brown.
• Give the species at least 6–8 m of space and keep it away from the house; dwarf forms fit in 1 m.

Light

Sun and partial shade

Soil type

Sand or loam

Acidity

Acid or neutral

Moisture

Normal or wet

Size

20 m tall, 8 m wide

Hardiness

Hardy (to -25 °C)

Goes well with

• Japanese maple: Fine leaves and autumn colour beside the dark green, in the same moist, acid soil.
• Rhododendron: Likes the same lime-free, moist soil and partial shade.
• Japanese forest grass: A soft, graceful edging at the base.
• Ferns: Fresh underplanting in partial shade.
• Heather: Low and colourful beside dwarf forms in a sunny, acid border.

Japanese cedar: 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 neither frozen nor bone dry.
2. Dig a hole twice as wide as the root ball and mix in a few spadefuls of leaf mould.
3. Set the tree at the same depth as it was in its pot or root ball and firm the soil well.
4. On a windy site, tie a young tree to a slanting stake.
5. Water generously straight away, then every week in dry weather during the first year.
6. Spread a mulch of leaf mould or wood chips around the base.

Care

Watering

Weekly in dry spells in the first year. Later on, water during long droughts too: it does not tolerate dried-out soil.

Feeding

Usually unnecessary. On poor soil, give a little compost or organic conifer fertiliser in April.

Mulching

A layer of leaf mould or wood chips in spring keeps the soil cool, moist and slightly acid.

Needle drop

In autumn the inner shoots turn brown and drop. This is normal and not a disease.

In a pot

Dwarf forms do well in a large pot of ericaceous compost. Never let the root ball dry out.

Tip: For a small garden, choose a dwarf form: the species itself becomes a 20 m tree over the years. Give it moist, lime-poor soil and keep it out of cold winds.

Japanese cedar: when to prune it?

Pruning months: April and August.

When: Pruning is rarely needed. If you want to shape or shorten it, do so in April or late August.

How:

• Cut out dead, damaged or brown branches back to healthy wood.
• Dwarf forms and hedges can be lightly trimmed; cut into the green shoots where possible.
• If a young tree has two leaders, remove the weaker one so that a single straight trunk remains.
• On a specimen tree the natural shape is the most beautiful: do only what is really necessary.

Caution: Do not prune in freezing weather or during a heatwave: the cuts and the needles will dry out.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Cuttings

In August–September: 10–15 cm semi-ripe cuttings with a heel, in moist cutting compost under glass or plastic. Roots form after a few months; garden forms stay true this way.

Seed

For the species only: sow in spring after a few weeks of cold in the fridge. Seedlings grow slowly.

Japanese cedar: how does it get through the winter?

Hardy to −25 °C.

• Hardy to about −25 °C: protection is rarely needed in Belgian winters.
• Cold, dry east winds can brown the needles. Protect young trees on an open site with a hessian windbreak.
• In a dry autumn, water well so the tree does not go into winter dried out.
• The bronze-red winter tint of forms such as ‘Elegans’ is normal; they turn green again in spring.

Diseases and pests

• Brown needles: After a dry summer or a cold, windy winter. Water in dry spells, choose a sheltered spot and snip out dead twigs.
• Inner needle drop: Brown twigs inside the tree in autumn are normal: they drop off by themselves.
• Red spider mite: Fine webbing and a dull, speckled colour in a hot, dry summer. Hosing the tree down and keeping the soil moist helps.
• Yellow needles: A sign of chalky or overly dry soil. Mulching with leaf mould and watering with rainwater helps.

Through the year

• January: Rest. Gently shake heavy snow off the branches.
• March: Spread a mulch of leaf mould.
• April: Planting. Light shaping if needed.
• May: Planting. Water young trees in dry weather.
• June: Water in dry weather. Watch for red spider mite.
• July: Water in dry weather.
• August: Light pruning. Take cuttings.
• September: Planting. Take cuttings.
• October: Planting. Brown inner twigs drop: this is normal.
• November: Put up a windbreak around young trees on an open site.
• December: Bronze-red winter tint on some forms.

Did you know?

• Despite its name it is not a true cedar (Cedrus): it belongs to the cypress family.
• Near Nikko in Japan there is an avenue tens of kilometres long, lined with thousands of sugi trees planted in the 17th century.
• The name Cryptomeria means ‘hidden parts’, a reference to the inconspicuous flowering and seed parts.