Chinese juniper

Identification and origin

Juniperus chinensis belongs to the Cupressaceae, the cypress and arborvitae family. It was long classified as Sabina chinensis. Its native range covers East Asia: northern, central and southeastern China, Inner Mongolia and Manchuria, Korea, Japan, Taiwan, Myanmar and the Russian Far East, from Sakhalin and the Kuril Islands to the Khabarovsk region.

The species itself forms an upright, conical tree 49–59 ft tall and 15–19.5 ft wide, with slow growth. Most plants you will meet, though, are its many cultivars and varieties, ranging from 18 in – 2 ft groundcovers to trees over 39.5 ft tall, in creeping, narrow, oval, pyramidal, rounded or upright forms.

Chinese juniper bears two kinds of leaves, often on the same plant:

• juvenile leaves, sharp, prickly needles about 0 in long, in pairs or threes;
• adult leaves, tiny, blunt, tightly pressed scales arranged in opposite pairs.

The aromatic foliage ranges from true green to blue-green or gray-green. The reddish-brown bark peels in vertical strips; on old plants it becomes ridged and furrowed.

The species is dioecious: each plant is either male or female. Yellow male cones look like tiny catkins. Female cones turn fleshy, forming a waxy-blue, berry-like cone about 0 in across, green at first and blue-gray by fall; they take two years to ripen, turning violet-brown to almost black. Birds eat them.

A few common selections:

• ‘Shimpaku’: a dwarf form widely used for bonsai; the ‘Itoigawa’ selection has fine, emerald-green foliage.
• var. sargentii: a groundcover 12 in – 2 ft tall and 8–10 ft wide.
• ‘Torulosa’: a small tree 15–19.5 ft tall with twisted, sculptural branches; ‘Kaizuka’ also has strongly sculptural branching.
• ‘Blue Point’: a dense pyramid 12 ft tall with blue-green foliage.
• ‘Pfitzeriana’: a wide-spreading shrub 5–7 ft tall and 15–19.5 ft wide; its foliage is highly flammable.

Light

Full sun suits it best, with at least six hours of direct light a day. It tolerates light partial shade. This is an outdoor plant: a juniper cannot live indoors for long; at most it can be brought inside for a day or two.

Watering

In the ground, an established plant tolerates moderate drought and is content with soil that stays just moist. After planting, or during a long dry spell, check soil moisture deep down and water thoroughly once it has dried, without following a schedule.

In a container, let the surface dry slightly between waterings without ever letting the root ball dry out completely, then water until it drains from the bottom. Above all, avoid overwatering: soil that stays soggy does not suit it.

Potting mix

Chinese juniper adapts to both acidic and alkaline soils, with a pH of about 5 to 8. What it needs most is good drainage: well-drained, gravelly soil suits it perfectly, whether on the dry or moist side. It tolerates air pollution, roadside de-icing salt, rocky soil and nearby black walnut. In a container, choose a basic bonsai mix or an even more free-draining, fine-grained mix.

Temperature

It is hardy in USDA zones 4a to 9b, which means winter lows of about -29 °F. In a container, the roots are far more exposed to frost than in the ground: protect them below about 14 °F, for example in a cold frame. In hard cold, some of the foliage can turn purplish-brown; this is a normal reaction and it greens up again in spring.

Repotting

In the ground, it transplants easily; plant it in sun and well-drained soil.

In a container, repot about every two years in early spring, in a free-draining mix; old specimens can wait longer. Do not prune the roots too hard: they are very fine.

Pruning

Juniper does not regrow from bare wood: new shoots grow only from tips that still carry foliage.

• When: any time except during hard freezes and in late summer. The best time is early spring, before new growth starts.
• How: cut each overlong branch just above an upward-growing side shoot, which hides the cut and keeps a natural shape.
• Avoid: shearing, especially after midsummer. The outer foliage becomes so dense that it shades the interior, which goes bare, and the plant browns more easily from cold and drying wind.
• Shape: keep the base wider than the top so the lower branches get enough light.

A plant that has outgrown its space cannot be rescued with hard pruning: prune early, or choose a more compact cultivar.

Propagation

• Cuttings: the most reliable method. In spring, take shoots from the previous year’s wood and dip the base in rooting hormone.
• Air layering: start in early spring; it sometimes takes two seasons before the layer is well enough rooted to be separated.
• Seed: possible, but since the species is dioecious, both male and female plants are needed to produce seed.

Common problems

A single symptom can have several causes: browning foliage can come from frost, drying wind, overwatering, overly hard pruning or a pest. Look closely at the plant before treating it.

• Cedar-apple rust and related rusts: woody, greenish-brown galls up to 2 in across form on the twigs. In wet spring weather they push out orange, jelly-like horns whose wind-borne spores infect apples, crabapples, pears or hawthorns. Chinese juniper is only occasionally affected and the galls do it little harm: cut them out for appearance. Fungicides are not recommended on juniper.
• Needle blight: it shows up in wet springs; some cultivars, such as ‘Sea Green’, are susceptible to phomopsis blight.
• Pests: spider mites, juniper scale, aphids, needle miners, webworms and bagworms. Overly dense foliage encourages them: thin it out.
• Deer: they seldom damage it.

Toxicity

The prickly foliage can cause contact dermatitis: wear gloves and long sleeves when pruning. Chinese juniper does not appear among the plants listed as toxic to dogs and cats; even so, keep children and pets from chewing the twigs or cones.