<em>Chamaecyparis</em>, false cypress: planting, pruning and care

Description and botany

Genus Chamaecyparis comprises around 6 species, although boundary with Cupressus is not always clear. For example, proposals exist to transfer Chamaecyparis nootkatensis to Cupressus. Two genera were even conflated during 19th century. These are often very large trees with strongly scented wood and foliage. European colonists who first encountered these conifers called them ‘cedar’ because of scent of their wood. A few morphological criteria nevertheless allow distinction. Persistent twigs of Chamaecyparis are flattened as in Thuja, whereas those of Cupressus are cylindrical. Cupressus have a straight leading shoot while Chamaecyparis have a supple, curved leading shoot. Globose cones are smaller than in Cupressus.

Chamaecyparis occupy cool, humid northern regions of North America and East Asia (Japan, Taiwan) where they typically mingle with other conifers in shaded, damp forests. Chen-mu or Sacred Tree (Chamaecyparis formosensis), with longevity exceeding 2,000 years, is among tallest trees of Taiwan, reaching 55–60 m with trunks up to 7 m wide, but rarely exceeds 15 m in cultivation. Chamaecyparis lawsoniana from North America can also reach 60 m alongside Douglas fir and live to 600 years. Chamaecyparis nootkatensis, Nootka cypress, also called “yellow cedar” for wood colour, found along Pacific coast up to Canada, reaches 36 m, as does Japanese cousin Hinoki (C. obtusa), a slow-growing species of which some specimens attain 50 m. Sawara (C. pisifera) can rise to 45 m in Japan.

Chamaecyparis obtusa – botanical illustration by P.F. von Siebold and J.G. Zuccarini

Foliage made up of scales in 4 ranks, more or less applied against the twig, is aromatic: parsley aroma in lawsoniana, cedar in obtusa, resin in pisifera, resin described as unpleasant in nootkatensis… There are cultivars that retain juvenile foliage of short needles as in Japanese Hinoki cypress ‘Wissel’ or Chamaecyparis thyoides Blue Rock. While C. lawsoniana shows bluish-green or dark matte green colouring, whitish beneath, C. obtusa displays an intense, very bright green on rounded twigs with attractive texture, and C. pisifera ‘Boulevard’ has feathery silvery-green foliage. Numerous cultivars of genus offer wide range of colours, textures and habits.

Bark often reddish, fibrous, forming long vertical strips.

Male and female flowering occur on same plant. Tiny male cones, greenish to yellowish, appear at tips of twigs and release pollen in March or April when female flowers develop at tips of other branchlets.

Globose cones are strobili, sometimes fleshy, softer and smaller (about 1 cm) than in Cupressus. Scales, numbering 4 to 10 depending on species, bear small point on upper side, a fold in lawsoniana. They ripen in autumn when scales open to release winged seeds but often persist on tree for long time. Seeds are released earlier than in Cupressus.

Wood of false-cypresses is fine-grained and durable, highly prized by Japanese for coffins, temples, lacquered furniture and prestigious houses. After extensive exploitation of Hinoki (C. obtusa) wood, Japanese importation of Lawson cypress wood from United States contributed to decline of populations already seriously affected by Phytophthora. Strict regulation now requires cleaning of tyres and footwear when entering these native forests.

Chamaecyparis lawsoniana: scaly foliage and globose cones

Main Chamaecyparis varieties

Dwarf varieties

Medium-development varieties

Chamaecyparis obtusa Teddy Bear - Hinoki Cypress

Small conifer with appearance of a large fern, with fine, dense foliage of a bright, quite intense green. Rather uncommon, its twisted silhouette fits elegantly into borders, stands out as a solitary specimen, enlivens rockeries and adapts well to growing in a pot. A curiosity to discover, easy to grow in ordinary, cool but well-drained soil, in full sun or partial shade.

• Height at maturity 1 m

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Chamaecyparis thyoides Blue Rock

Very recent rare species of dwarf conifer, with sumptuous foliage forming a compact ball with fine texture, initially blue-green, taking on violet to purple tones in winter. It has very slow growth, not exceeding 1.50 m in any direction at ripeness. Perfect in rockeries, small spaces or container culture, in sunny or semi-shaded aspect, in soil that remains cool, light and well-drained, humus-bearing and rather acidic.

• Height at maturity 1,50 m

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Chamaecyparis obtusa Kamarachiba - Hinoki Cypress

Dwarf variety with a slightly loose rounded habit, somewhat hirsute and slightly flared. Its flat, lemon-yellow branches marked with cream trail gracefully in a charmingly calculated disorder, turning to a copper-bronze in winter. Brings life to small spaces, borders, rockeries or a container all year round. Prefers sunny or semi-shaded aspect, fertile soil, rather cool but well-drained, not too calcareous.

• Height at maturity 1,25 m

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Chamaecyparis lawsoniana Green Globe - Lawson Cypress

Miniature bush, forming a bright green ball with very dense foliage in youth which becomes more tousled with age. Not exceeding 50 cm at adult age, it grows slowly and is particularly suited to permanent decoration of rockeries and containers. Enjoys sun and cool, fertile soils, neutral to acidic.

• Height at maturity 50 cm

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Chamaecyparis pisifera Boulevard - Sawara Cypress

Remarkable variety for its soft, variegated blue-green panache foliage whose silvery highlights beautifully catch the light, as if the bush were in perpetual motion. Built in a slightly loose cone, it takes on faint violaceous hues under the effect of cold. This slow-growing conifer prefers sunny or semi-shaded exposure, soil that is rather cool but light and well-drained, humus-bearing.

• Height at maturity 2,50 m

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Chamaecyparis lawsoniana Yellow Spire - Lawson Cypress

Rockery conifer forms a somewhat gangly bush, with a very narrow conical habit and a very graphic silhouette. Its feathery, curiously twisted branches are covered in spring with very bright yellow-green young foliage, becoming blue-green with age. Not exceeding 1.40 m in height at adult age, it has slow growth and is particularly suited to permanent decoration of small spaces, rockeries and containers. Enjoys sun and cool, fertile soils, slightly calcareous, neutral or slightly acidic.

• Height at maturity 2,75 m

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Chamaecyparis obtusa Aurea - Hinoki Cypress

Majestic Japanese conifer displaying a conical, dense and rounded silhouette, adorned with twisted golden-yellow branches in spring and then light green. Thrives in full sun, in cool, deep, well-drained soil.

• Height at maturity 9 m

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Chamaecyparis pisifera Filifera - Sawara Cypress

Wide and dense bush, later becoming pyramidal, with supple and slightly trailing foliage, bright to dark green. Its dishevelled appearance gives it a rather appealing languid charm. Perfect in rockeries and small spaces in sunny or semi-shaded aspect, in soil that is rather cool but light and well-drained, neutral or acidic.

• Height at maturity 5,50 m

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Chamaecyparis obtusa Snowflake - Hinoki Cypress

With its fern-like foliage studded with bright spots, it rivals flowering bushes and will become a magnificent specimen planted alone in a small space or in a pot. Young spring foliage very compact, grey-green, randomly splashed with light, the tips variegated with cream-white or even grey turning to shadowy green in summer. For ordinary, cool but drained soil, in sun or partial shade.

• Height at maturity 1,80 m

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Planting

Where to plant Chamaecyparis?

Chamaecyparis are not demanding about soil, provided it is deep, cool and well drained. They prefer cool conditions, not too sunny to semi-shaded. As a rule, avoid climates that are too dry and poorly drained soils.

These conifers will also tolerate poor soil with moderate growth and reduced vigour, which can be useful when aiming to keep the specimen small. Some cultivars are more sensitive than others such as C. pisifera ‘Boulevard’ or C. thyoides ‘Blue Rock’, which both dislike calcareous soils as well as excessive sun for the former and wind for the latter. C. lawsoniana ‘Pottenii’ browns under drying winds or severe winters… Chamaecyparis lawsoniana ‘Ellwoodii’ with its grey-blue foliage, darker in winter, tolerates shade well.

Beware of soils waterlogged in winter which can favour development of Phytophthora cinnamomi if the fungus is present in soil, because the lawsoniana species is very sensitive to it.

When to plant?

Prefer planting in autumn (October–November) or in February–March.

How to plant?

This plant is generally very easy to grow.

To create a clipped Chamaecyparis hedge, space young plants 80–100 cm apart, and up to 2 m apart if forming a windbreak left to its natural habit.

• Soak the pot in a bucket of water to ensure it is thoroughly moist.
• Dig a wide hole at least three times wider than the rootball because roots remain fairly shallow and spread widely.
• Add a few handfuls of sand and gravel to ensure good drainage around roots. In heavy soil, opt for planting on a mound or within a rockery.
• Apply a dose of ground horn if soil is sandy.
• Place the plant in the planting hole.
• Replace soil and firm down lightly.
• Water and mulch.

In a pot, use a light humus-bearing soil or mix ¾ garden soil with ¼ pouzzolane and ¼ potting compost. Choose slow-growing plants such as Chamaecyparis obtusa ‘Pygmaea’ or pisifera ‘Boulevard’.

Chamaecyparis obtusa ‘Nana Gracilis’

Care and pruning

Potted young plants require regular watering, especially when sun is scorching. Water young plants properly for first 2–3 years.

Main pests and diseases of Chamaecyparis

Chamaecyparis is generally a bush that does not cause maintenance problems when soil is healthy and it does not suffer long dry periods. However, its use as a single-species hedge can sometimes lead to rapid infections such as more or less severe drying out of branches, which can be caused by:

• cryptogamic browning which appears during wet springs on lower branches. Apply a copper-based fungicidal every 15 days or a horsetail decoction, or cut and burn affected twigs.
• Phytophthora to which Chamaecyparis is very sensitive, causing progressive drying out of the entire tree due to necrosis of tissues of the collar and roots under the bark. Uproot and burn and plant non-susceptible species.
• cortical canker which particularly affects Leyland cypress (x Cupressocyparis leylandii), a hybrid between a Cupressus and a Chamaecyparis. It causes cracking of the bark and resin oozing accompanied by black pustules. Cut and burn affected branches, seal wounds with mastic. Uproot if trunk is affected.
• root rot (Armillaria) favoured by heavy, damp soils, which causes sudden drying out of the young plant accompanied by a strong fungal smell. Uproot and leave the planting hole exposed to air for a season. Replace the soil.
• colonies of aphids (apply an insecticidal treatment quickly, such as soapy water or fern manure),
• the juniper buprestid which bores galleries into the wood and causes browning in summer. The only solution is to cut and burn the swollen twigs.

Pruning of Chamaecyparis

These bushes or trees are not fond of pruning, so it is preferable to use them in natural habit if you wish to form hedges. Always perform very light pruning in August if necessary, ensuring foliage is always retained.

Multiplication

Simplest propagation method is to propagate a large number of semi-ripe twigs in August–September as success is not guaranteed.

Propagation by cuttings

Prepare a tray by filling it with a mixture of half turf and half sand, or prepare soil in a nursery bed.

• Take 10 cm long shoots by pulling to retain a strip of bark.
• Remove branching near base of shoot.
• Insert these to one-third of their length, avoiding any contact between them.
• Firm gently all around to remove air pockets and ensure good contact between growing medium and cutting.
• Place a cold frame over them and a shade cloth until spring.
• Separate cuttings and replant in pots or in ground in a nursery for 1 to 2 years, or plant directly in place if soil is favourable

  → Discover our tutorial : How to take cuttings from conifers?

Uses and companion plants

Use Chamaecyparis for their uniqueness as isolated specimens in middle of a short grass meadow or as background to a flowering border such as Chamaecyparis obtusa ‘Nana Gracilis’ with erect, mounding habit reaching 2 m at maturity, which unfolds clouds of dark green, shell-shaped foliage. Some form a perfect cone like Lawsoniana ‘Columnaris’ while others form a curtain 6–8 m in diameter and 10–15 m high like C. nootkatensis ‘Glauca’.

A planting idea: Chamaecyparis thyoïdes ‘Rubicon’ (or ‘Blue Rock’ or other) on a luminous tapetum of heather Erica darleyensis ‘Eva Gold’, a few clumps of Festuca glauca and some balls of Berberis thunbergii ‘Atropurpurea Nana’

Small Chamaecyparis thanks to slow growth make perfect candidates to ornament a rockery, a small garden or a terrace when grown in a pot. With their very natural silhouette that does without pruning, they have remarkable graphic qualities suited to contemporary gardens as well as natural gardens. They combine well with other dwarf conifers such as Thuyas, Junipers, Cryptomerias or with flowering bushes for acidic soil and cool areas such as azaleas, andromedas, heathers or camellias. They can also be trained into clouds or bonsai such as species obtusa ‘Aurea’ whose masses of golden foliage contrast nicely with dark colour of the trunk.