Cryptomeria, Japanese Cedar: Planting, Pruning and Care

Description and Botany

The Cryptomeria japonica (syn. fortunei) belongs to the Taxodiaceae family, like the Bald Cypress (Taxodium distichum), the American Sequoias or the Chinese Metasequoia, but its leaves resemble no other conifer. They consist of pointed but not sharp claws, 1 cm long, arranged awl-like around the branchlet, whose smooth and rather flexible texture resembles plastic. The evergreen leaves eventually renew after a few years but in a peculiar way, as entire branchlet sections turn brown before falling, a phenomenon called decuritation, also observed in Araucaria.

The Japanese Cedar reaches impressive dimensions up to 30-55 m in height, with a very slender habit and rapid growth of about 6 to 8 m in 10 years in Japan’s rainforests. Its longevity may reach 1000 to 2000 years according to a specimen at Misaka Shrine in Nagano, standing 30 m tall with a trunk 4 m in diameter at the base. Its reddish-brown bark peels in vertical strips. Its distribution area in the warm mountainous regions of Japan and southern China between 1000 and 2500 m altitude demonstrates its great adaptability, especially as this species existed during the time of dinosaurs. There is some variability between Japanese and Chinese specimens. Cryptomeria japonica var. sinensis has a less rigid habit due to finer branchlets. Moreover, Japanese researchers found that above 1750 m, Cryptomeria propagates solely by layering, while more favourable conditions also allow sowing, leading to greater genetic diversity.

Cryptomeria japonica – botanical illustration

The species has given rise to over two hundred cultivars, including compact dwarf forms with very slow growth and extremely short needles like Vilmoriniana, or forms with soft, airy foliage like Elegans or Elegans Viridis. The leafy branchlets of cultivars often take on an exceptional reddish-bronze to rusty colour in cold weather, particularly in the Elegans cultivar, whose columnar habit reaches up to 9 m tall and 2.40 m wide, or even more when it begins layering and forms a grove! The variety Cryptomeria japonica var. cristata produces fused, flattened shoots resembling a cockscomb, adding an incongruous note to the scene.

Flowering is monoecious; the male aments form small terminal clusters in winter, releasing abundant pollen in February-early March. The female flowers form tiny green rosettes at the tips of branchlets, which swell after fertilization to reach 1.5 cm in diameter by autumn before browning and releasing their seeds the following autumn. Each cone has about forty scales ending in a recurved point.

The Japanese Cedar is widely used as an ornamental plant in temperate gardens worldwide, in Europe, India, North America, and Australia, while it serves as an important forest tree in Japan, China, the Azores, and Réunion. It is also deeply revered in Japan, particularly in Nikko near Tokyo, where a row of nearly 14,000 specimens, aged four centuries, lines a 37 km avenue. Its highly fragrant but rather soft wood is prized for temple construction and coffins in China, and is also used in furniture, building, and panelling as it resists fungal and insect attacks well, likely due to its essential oil content.

The main varieties of Cryptomeria

Upright varieties with moderate vigour

Compact varieties in ball or conical shapes

Cryptomeria japonica Sekkan-Sugi

Graceful and original conifer with semi-trailing branches covered in light green foliage adorned with pale yellow young shoots turning cream to almost white in winter. Its feathery-looking branches, very soft to the touch and pleasing to the eye, gracefully brighten up a semi-shaded corner.

• Height at maturity 6,50 m

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Cryptomeria japonica Yokohama

Dwarf evergreen conifer with a rounded habit becoming conical with age, featuring slightly irregular growth. Extremely fine and dense, almost crisped foliage, pale green in summer, purple-bronze in winter. Its tender green young shoots make it a very luminous plant for rockeries or containers in moderate sun.

• Height at maturity 1,10 m

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Cryptomeria japonica Vilmorin Gold

Dwarf conifer with a somewhat irregular rounded and compact habit, featuring very dense evergreen foliage of a beautiful true green adorned with superb golden shoots turning cream in summer. This slow-growing variety, limited to 1m, allows for unexpected and colourful combinations in sunny rockeries and alpine gardens.

• Height at maturity 1 m

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Cryptomeria japonica Vilmoriniana

Compact ball of luminous green that develops lovely brown and red hues under cold conditions. Limited development in containers of 30cm in all directions. Ideal for decorating small gardens, rockeries or terraces. It thrives in sun, in ordinary well-drained soil, not too dry to fresh.

• Height at maturity 90 cm

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Planting

Where to plant Cryptomeria?

Cryptomeria thrives in ordinary, fairly moist, well-drained, rather fertile soil, even slightly chalky, neutral or acidic. It dislikes excessively dry or shallow soils. It particularly enjoys the mild and humid climate of the Atlantic coast but adapts fairly easily elsewhere, though its dimensions remain more modest.
Plant it in full sun if the climate allows, except for cultivars with light foliage like Sekkan Sugi, which fare better in partial shade to avoid sun scorch. Position the young plant sheltered from dry, cold winds, which can scorch young shoots, and in partial shade in southern regions. Minimum temperatures range from -15°C to -20°C depending on the clone, though branches struggle under heavy snow.
Dwarf forms tolerate planting in deep containers, which slows their growth and helps maintain a more compact habit. They also suit rockeries, provided they’re not too sunny or windy, as the plant seeks atmospheric moisture. The roots can draw humidity from beneath rocks. Bonsai cultivation is common with Cryptomeria.

Male aments of Cryptomeria japonica

When to plant?

Cryptomeria japonica is best planted from September to November and February to June. In mild, well-watered climates, pot-grown specimens can be planted almost year-round, avoiding extreme cold or heat.

How to plant?

With smaller young plants (50cm tall), such as 2-year-olds, establishment is very easy.

• Soak the pot in a bucket of water to moisten thoroughly.
• Dig a hole 3 times wider than the rootball and aerate the surrounding soil with a fork.
• Add manure or compost to ensure strong early growth, as the tree can grow quite quickly.
• Place the plant in the planting hole.
• Backfill and firm gently, creating a shallow basin.
• Mulch to retain moisture and water with at least 10 litres.

For deep, large containers, add a drainage layer (gravel, clay pebbles, crocks…), then a mix of 1/3 garden soil, 1/3 sand and 1/3 heather soil, turf or well-rotted compost. Mulch the pot surface.

Maintenance

• Water the Cryptomeria generously during the first 3-4 years, and during prolonged dry spells. The young plant becomes fairly self-sufficient quite quickly unless grown in a container. Remember to mist the water regularly on specimens trained as bonsai.
• Apply a specialist conifer fertiliser every year in April and hoe the soil in summer to prevent capillary rise if you don’t have mulch.
• You can leave fallen dry twigs on the ground to form a natural mulch.
• Protect young plants with winter fleece if winters are cold.
• Pruning is not necessary. Dwarf forms may undergo light pruning of branches in March-April or late summer (August-September), just like Cryptomeria japonica ‘Elegans’ which dislikes hard pruning!
• There are no reported diseases or pests affecting Cryptomeria in Europe. Honey fungus (Armillaria) has been reported in some countries like Hawaii under warm, humid conditions.

Cones of Cryptomeria japonica

Propagation

The simplest method of propagation involves taking cuttings from Cryptomeria and its cultivars between August and October or sowing seeds of the species type in spring.

Propagation by cuttings

Prepare a deep pot by filling it with 50% turf and 50% sand.

• Take 15 cm long semi-hardwood cuttings from the most vigorous shoot tips.
• Remove the needles from the base of the cutting.
• Dip the base in plant hormone for cuttings.
• Insert them two-thirds of their length into the soil, ensuring they do not touch each other.
• Gently firm the soil around them to eliminate air pockets and ensure good contact between the compost and the cutting.
• Place them in a humid, shaded environment, for example by covering them with a transparent plastic bottle cut in half.
• Remove the plastic after a month and keep your cuttings warm, protected from direct sunlight.
• Wait 4 to 6 months for sufficient root development.→ Discover our tutorial: How to propagate conifers from cuttings?

Sowing

• Obtain seeds from a reputable seed supplier.
• Stratify them for a few days in the refrigerator.
• Sow them in a tray filled with compost mixed with sand.

Uses and Combinations

The varieties of Cryptomeria have often been selected for the seasonal colour variations they offer, starting with a very bright green in spring that darkens in summer before turning reddish, sometimes even taking on fiery hues with the cold, as seen in Vilmorinia or Elegans. Their ball-shaped forms in Compressa, conical in Yokohama, decidedly weeping in Sekkan Sugi, and columnar in Elegans provide a range of possibilities for pairing with other low-growing evergreen bushes or for creating a hedge. Don’t hesitate to plant them alongside bushes with small, glossy, richly coloured leaves such as Abelia Sparkling Silver, Berberis darwinii or thunbergii Orange Dream or Golden Carpet. Heathers and other dwarf conifers with bluish tones like Juniperus squamata Blue Star are among the many options for accompanying Cryptomeria in a rockery or on a terrace. This plant, with its unique silhouette and foliage texture, pairs well with large stones, geometric lines, and masonry work.

An autumn pairing idea: Cryptomeria japonica ‘Sekkan Sugi’, Acer palmatum ‘Dissectum’, Acer palmatum ‘Shindeshojo’, Euonymus alatus and Picea glauca Cecilia’

Cryptomeria japonica Sekkan Sugi, with its snow-covered fir-like appearance, understated elegance, and moderate growth reaching up to 6.50 m in height and 3.5 m in width, deserves a place in the garden. It can brighten up partially shaded areas or serve as a low-maintenance, luminous backdrop for flower beds, thanks to its cream to almost white foliage in winter. It can thus highlight the flowering of a fragrant wild camellia such as Camellia lutchuensis.

The standard species Cryptomeria japonica, often featuring multiple straight trunks and permanent dark green, reptilian-like foliage, is a remarkable choice for an average-sized garden that will make a striking standalone feature, especially as it remains modest in size, reaching around 10 m in height and 3 to 5 m in diameter. Alternatively, pair it with maples, ginkgos, or liquidambars to create a striking autumn contrast.