Hinoki cypress

Identification and origin

Chamaecyparis obtusa belongs to the Cupressaceae. It is a “false cypress”: the true cypresses make up the genus Cupressus. It is native to Japan and Taiwan. On Taiwan grows its variety formosana, in broadleaf or mixed mountain forests between 4,265 ft and 9,186.5 ft above sea level, in pure stands or mixed with another false cypress. Long grown in Japan as an ornamental and for its timber, one of the country’s most valuable, it is also widely used there for bonsai. It was introduced to Britain in 1861.

In its homeland it is a large tree of 98.5–121.5 ft, with a reddish-brown trunk that can reach 3.5–10 ft across. In cultivation it is more likely to reach 50–75 ft tall and 10–25 ft wide. It has a broad, soft pyramidal outline with horizontally spreading branches, and grows slowly to moderately.

The evergreen foliage is made of tiny scale leaves in two sizes, thick, fleshy and rounded at the tip. That blunt tip sets it apart from Sawara cypress, whose scales are pointed, and from Lawson cypress. The scales, deep green on top, cover flattened twigs arranged in fans. Their undersides carry whitish lines forming X or Y shapes, a good identification feature. The reddish-brown bark peels away in fibrous strips.

The small, often reddish pollen cones appear at the branch tips. The seed cones are almost round, about 0–0 in across, and usually have eight to ten scales; green at first, they ripen to orange-brown.

There are countless cultivars. Dwarf forms include ‘Nana Gracilis’, with dark green foliage, which reaches 5–8 ft in cultivation and sometimes much more with age; ‘Nana’, about 3 ft; and compact ‘Chirimen’ and ‘Pygmaea Aurescens’. Others stand out for their color: ‘Crippsii’, ‘Nana Lutea’ and ‘Fernspray Gold’ are golden, ‘Tetragona Aurea’ has fern-like fronds, ‘Blue Feathers’ is blue-green and ‘Coralliformis’ has twisted, reddish twigs.

Light

Hinoki cypress grows best in full sun, with at least six hours of direct sun a day, facing east, south or west. It tolerates part shade, but a golden cultivar such as ‘Tetragona Aurea’ needs sun to keep its color. In shade, the inside of the tree thins out: scales deprived of light turn brown and do not grow back. Shelter it from strong wind, especially in winter.

Watering

It likes moist but well-drained soil and handles drought poorly. In the ground, keep the soil moist, especially during dry spells.

In a container or as a bonsai, it is thirstier than most conifers. Water as soon as the mix starts to dry, without leaving the roots constantly soaked. Use lime-free water, such as rainwater, when you can. In winter, water less but never let the root ball dry out completely. The foliage enjoys humid air and suffers in hot, dry wind.

Potting mix

It prefers fertile, moist, well-drained loam. It adapts to clay or sandy soils if water drains well and tolerates chalky soil, but it grows best in slightly acidic soil and does poorly on very limy ground. On poor soil it thins out with age. In a container, choose a free-draining, slightly acidic mix; in hot climates, add a little humus to hold more water.

Temperature

This hardy conifer suits USDA zones 4a to 8b and withstands cold down to -4–5 °F. In a container its roots are more exposed, so protect it from hard frost and icy wind while still giving it plenty of light. The Taiwanese variety, formosana, is less hardy and only rated to USDA zone 7.

Repotting

In the ground it is difficult to transplant, so choose its permanent spot carefully. As a bonsai, repot a young tree every two to four years and an old one less often, in spring as growth begins. Its roots grow quickly and tolerate fairly heavy pruning.

Pruning

In the ground it needs no pruning. A hedge is trimmed twice a year to keep its shape. Pinching shoot tips makes the branching denser, which helps trees that are thinning out. It does not sprout from old wood: only branches that are still green produce new buds, so never cut back beyond the foliage. On ‘Nana Gracilis’, often grafted, remove vigorous shoots that revert to the species form.

Propagation

Hinoki cypress is propagated from seed and semi-ripe cuttings. Seeds need a cold period before they germinate, which can take up to a year; sow them outdoors in spring. Take cuttings in late summer. Air layering is done in late spring. ‘Nana Gracilis’ is usually grafted, and its rootstock often forms an unsightly swelling at the base of the trunk.

Common problems

Browning foliage can have several causes: lack of light inside the canopy, drought, overwatering, overly limy soil, cold wind, pests or disease. Look at the whole tree before acting.

• Pests: aphids, scale (including juniper scale), spider mites, bagworms and moths whose caterpillars bore into the shoots.
• Diseases: honey fungus, Phytophthora root rot in soil that stays too wet, and tip blight, which kills the ends of the shoots.
• Growing conditions: very limy soil, poor drainage, shade, and the natural thinning of interior foliage with age.

Toxicity

No toxicity has been reported: hinoki cypress does not appear among the plants that veterinary references list as toxic to dogs and cats. Even so, keep children and pets from chewing its foliage or cones.