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

Description and botany

Genus Chamaecyparis comprises around six species, the boundary with Cupressus not always clear. For example, transfer of Chamaecyparis nootkatensis to Cupressus has been proposed. The two genera were even confused in 19th century. They are often very large trees with very aromatic wood and foliage. European colonists who first encountered these conifers called them ‘cedar’ because of scent of their wood. Some morphological criteria nevertheless allow differentiation. Persistent twigs of Chamaecyparis are flattened as in Thuja, whereas those of Cupressus are cylindrical. The latter have a straight leading shoot while Chamaecyparis have a flexible, curved leading shoot. Their globose cones are smaller than those of 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), whose longevity exceeds 2,000 years, is among largest trees of Taiwan, reaching 55–60 m with trunks up to 7 m wide, although it rarely exceeds 15 m in cultivation. Chamaecyparis lawsoniana from North America can also reach 60 m alongside Douglas-fir (Pseudotsuga) and may live to 600 years. Chamaecyparis nootkatensis, Nootka cypress, also called “yellow cedar” for colour of its wood, found along Pacific coast up to Canada, reaches 36 m, as does Japanese cousin Hinoki (C. obtusa), which grows slowly though some specimens attain 50 m. Sawara (C. pisifera) rises to 45 m in Japan.

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

Foliage made of scales arranged in four ranks, more or less applied against twig, is aromatic: smell of parsley in lawsoniana, of cedar in obtusa, of resin in pisifera, resin described as unpleasant in nootkatensis… There are cultivars that retain juvenile foliage in form of short needles as in Japanese hinoki cultivar Wissel or Chamaecyparis thyoides Blue Rock. While C. lawsoniana shows bluish-green or dark matt green colouring, paler beneath, C. obtusa displays an intense, very bright green on rounded twigs with very attractive texture and C. pisifera ‘Boulevard’ has feathery silvery-green foliage. Numerous cultivars of genus offer very 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 twig tips and release pollen in March or April when female flowers develop at ends of other twigs.

Globose cones are strobili, sometimes fleshy, less hard and smaller (about 1 cm) than in Cupressus. Scales, numbering four to ten depending on species, bear a small point on upper surface, a fold in species lawsoniana. They mature in autumn when scales separate to release winged seeds but 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 coffin-making, temples, lacquered furniture and prestigious houses. After extensive exploitation of Hinoki (C. obtusa), Japanese imported Lawson cypress wood from United States, contributing to decline of populations already seriously affected by Phytophthora. Strict regulations now require cleaning of tyres and footwear when entering these native forests.

Chamaecyparis lawsoniana: scale foliage and globose cones

Main varieties of Chamaecyparis

Dwarf varieties

Medium-sized varieties

Chamaecyparis obtusa Teddy Bear - Hinoki Cypress

Small conifer with appearance of a large fern, bearing fine, dense foliage of a vivid green shade. Not widespread, its twisted silhouette fits elegantly into borders, stands out as an individual specimen, enlivens rockeries and adapts well to container culture. A curiosity to discover, easy to grow in ordinary, cool but well-drained soil, in sun or partial shade.

• Height at maturity 1 m

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Chamaecyparis thyoides Blue Rock

Rare, very recent dwarf conifer species with sumptuous foliage forming a compact, fine-textured ball, initially blue-green, taking on violet to purple hues in winter. Grows very slowly, not exceeding 1.50 m in any direction at ripeness. Perfect in rockeries, small spaces or container culture, in sun or partial shade, 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 somewhat loose rounded habit, slightly hairy and a little flared. Its flat, lemon-yellow branches marked with cream fall gracefully in a charmingly contrived disorder, turning coppery-bronze in winter. Brings year-round interest to small spaces, borders, rockeries or a container. Prefers sun or partial shade, fertile soil that is 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 that becomes more tousled with age. Not exceeding 50 cm at adulthood, grows slowly and is especially suitable for permanent decoration of rockeries and containers. Likes sun and soils that are cool, fertile, neutral to acidic.

• Height at maturity 50 cm

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Chamaecyparis pisifera Boulevard - Sawara Cypress

Remarkable variety for its soft, blue-green panache foliage whose silvery highlights catch the light attractively, as if bush were in perpetual motion. Built in a slightly loose cone, it takes on slight purplish tints under cold. This slow-growing conifer prefers sun or partial shade, 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 that forms a somewhat lanky bush with a conical, very narrow habit and a striking silhouette. Its curiously twisted, feathery branches are covered in spring with very bright yellow-green juvenile foliage, becoming blue-green with age. Not exceeding 1.40 m in height at adulthood, grows slowly and is particularly suited to permanent decoration of small spaces, rockeries and containers. Likes sun and soils that are cool, fertile, 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 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

Broad, dense bush that later becomes pyramidal, with supple, slightly trailing foliage, bright to dark green. Its tousled appearance gives a rather charmingly languid look. Perfect in rockeries and small spaces in sun or partial shade, 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 fern-like foliage sprinkled 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, with tips variegated in cream-white or even grey turning to shaded 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 type, provided it is deep, cool and well-drained. They prefer cool, not-too-sunny to semi-shaded situations. Generally, avoid overly dry climates and poorly drained soils.

These conifers will also tolerate poor soil with moderate growth and reduced vigour, which is not necessarily a bad thing if you want 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 harsh winters… Chamaecyparis lawsoniana ‘Ellwoodii’, with its grey-blue foliage, darker in winter, tolerates shade well.

Beware waterlogged soils in winter which may favour development of Phytophthora cinnamomi if the fungus is present in the soil, as species lawsoniana is very sensitive.

When to plant?

Prefer autumn (October–November) to plant Chamaecyparis, or 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 if it is a windbreak left in free habit.

• Immerse the pot in a bucket of water to thoroughly moisten it.
• Dig a wide hole at least three times wider than the rootball because roots remain fairly superficial 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 horn meal if soil is sandy.
• Place the plant in the planting hole.
• Backfill with soil and firm lightly.
• Water and mulch.

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

Chamaecyparis obtusa ‘Nana Gracilis’

Care and pruning

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

Main pests and diseases of Chamaecyparis

Chamaecyparis is generally a bush that causes no maintenance problems when soil is healthy and it does not suffer long periods of drought. However, using it in a single-species hedge can sometimes lead to rapid contagion such as more or less severe drying of branches which can be caused by:

• cryptogamic browning which appears during wet springs on lower branches. Apply a fungicidal treatment every 15 days based on copper or horsetail decoction, or cut and burn affected branches.
• Phytophthora to which Chamaecyparis is very susceptible, causing progressive drying of the entire tree due to necrosis of tissues at the collar and roots under the bark. Uproot and burn infected plants and replant with non-susceptible species.
• cortical canker which particularly affects Leyland cypress (x Cupressocyparis leylandii), a hybrid between Cupressus and 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 wet soils, which causes sudden drying of the young plant accompanied by a strong fungal smell. Uproot and leave the hole open to the air for one season. Replace the soil.
• colonies of aphids (apply an insecticidal treatment quickly such as soap or fern manure),
• juniper buprestid which bores galleries in the wood and causes browning in summer. The only solution is to cut and burn swollen branches.

Pruning Chamaecyparis

These bushes or trees do not much appreciate pruning so it is preferable to use them in a natural habit if you wish to form hedges. Always carry out very light prunings, performed in August if necessary, always retaining foliage.

Multiplication

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

Propagation by cuttings

Prepare a box by filling it with a mix composed of half turf and half sand, or work nursery soil.

• Take shoots 10 cm long, pulling on them to retain a strip of bark.
• Remove branching located near base of the shoot.
• Insert these to one-third of their length, ensuring they do not touch.
• Firm down gently all around to eliminate air pockets and ensure good contact between potting mix and cutting.
• Place a cold frame over them and a shade cloth until spring.
• Separate the cuttings and replant in pots or in nursery ground for 1 to 2 years, or plant directly in situ if soil is favourable

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

Uses and companion plants

Use Chamaecyparis for their uniqueness as solitary specimens in the middle of a short grass meadow or as a backdrop to a flowering bed such as Chamaecyparis obtusa ‘Nana Gracilis’ with an erect, mounded habit reaching 2 m at maturity, which unfolds clouds of shell-shaped dark green foliage. Some form a perfect cone like lawsoniana Columnaris while others form a curtain 6 to 8 m in diameter and 10–15 m tall 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 a few mounds of Berberis thunbergii ‘Atropurpurea Nana’

Small Chamaecyparis, because of slow growth, make perfect candidates to adorn a rockery, small garden or a terrace when grown in pots. With their very natural silhouettes that do without pruning, they have remarkable graphic qualities suited to contemporary gardens as well as natural gardens. They pair with other dwarf conifers such as thuyas, junipers, cryptomerias or with flowering bushes for acidic soils and cool areas such as azaleas, Pieris, heathers or camellias. They can also be trained into clouds or into bonsai like species obtusa ‘Aurea’, whose masses of golden foliage contrast nicely with the dark colour of the trunk.