The Juniper Bonsai: The Essence of Tenacity

When we think of a Japanese bonsai, the image is almost always that of a Juniper (Juniperus) with its sinuous curves and the dramatic contrast between the red live vein and the white deadwood (jin and shari). It is an extremely long-lived and flexible conifer, loved by masters for the possibility of creating complex, sculptural shapes. The most widely used varieties are Juniperus Chinensis (var. Itoigawa or Shimpaku) for its soft scale-like foliage, and Rigida for its needle foliage.

Origin & species

Widespread throughout the northern hemisphere. Junipers are pioneer trees, able to live in rock crevices with very little soil. In bonsai the "scale" varieties are preferred (they look like little green cords) because they are more compact and softer than the "needle" ones (prickly).

Position and microclimate

The Juniper must live outdoors, all year round.
It loves full sun, which keeps the foliage compact and prevents fungal attacks. Only in high summer, in hot Mediterranean climates, does light afternoon shade protect the bright green colour, but it is not strictly necessary if the tree is well watered.

Watering

Unlike broadleaves, the Juniper does not warn you straight away when it is thirsty (it does not wilt its leaves), but dries out its branches weeks after the damage.
Touch the soil: water only when it is dry. It does not like permanent waterlogging. It does, however, greatly enjoy misting over the canopy (even daily in summer, in the evening), which cleans dust from the stomata and hydrates the scales.

Water quality

It tolerates tap water, but prefers water that is not excessively hard.

Soil mix

Drainage is life. Juniper roots need a great deal of oxygen.

• Recommended mix: 60% Akadama and 40% Kiryuzuna (a specific Japanese grit for conifers that does not break down).
• As an alternative to Kiryu, use good quality pumice. Avoid pure organic soil mixes.

Repotting

Conifers are repotted less often. Every 3-5 years.
When: In late spring, when you see the tips of the foliage starting to move (April-May), or in early autumn.
Never bare-root wash the roots: the juniper lives in symbiosis with a beneficial fungus (mycorrhiza). Always leave part of the old soil around the root core to preserve this bacterial flora.

Fertilizing

Fertilize generously in spring and autumn with solid organic fertilizer (such as "biogold" or pellets). Stop in summer and winter. A well-fed juniper will have a dark green colour and will respond better to styling work.

Flowering and fruiting

It produces blue/purple berries, used for gin or in cooking. In bonsai they are often removed so as not to waste energy, unless you want a touch of winter colour.

Pruning and pinching (essential!)

Never use scissors to shorten the tufts of foliage! If you cut the scales with scissors, the tips will turn brown and ugly.
The pinching technique is used (with the fingers): take hold of the little tuft growing beyond the silhouette and gently pull away the new tip, breaking it off at the base. This keeps the foliage pads compact and green.

Wiring & bending

The Juniper is the king of wiring. Its wood is extremely flexible and withstands extreme twisting. It can be wired at almost any time, preferably in winter or autumn. Use copper wire (or aluminium for beginners) and wet raffia to protect the branches during heavy bends.

Deadwood (jin and shari)

Creating stripped wood areas (jin = dead branch, shari = stripped trunk) is typical of the juniper. Once created and dried, the wood should be treated with jin liquid (lime sulphur) twice a year to bleach it and protect it from rot.

Diseases and pests

• Red spider mite: Enemy number one. It turns the canopy grey/yellowish. Mist often and use acaricides.
• Scale insect: It hides inside the dense foliage pads.
• Juniper rust: Orange gelatinous growths on the branches (caused by proximity to wild pears/rosaceae).

Winter & protection

It is a mountain tree. It does not fear the cold and in fact needs it for dormancy. In case of exceptional frosts, protect the pot, but the canopy must feel the winter. In winter the foliage may turn bronze/purplish: this is normal protection against the cold, and it will turn green again in spring.

Yearly calendar

• January-February: Deadwood work, heavy wiring.
• March-April: Repotting (if needed), start fertilizing.
• May-June: Constant pinching of the foliage.
• July-August: Check for red spider mite, evening showers.
• September-October: Pinching, autumn fertilizing.
• November-December: Cleaning out old inner needles, jin liquid.

Useful products for this bonsai

• Kiryuzuna (specific soil mix for conifers)
• Jin liquid (to bleach the deadwood)
• Biogold fertilizer (the best for junipers)
• Copper-coloured aluminium wire (to shape the branches)
• Deadwood carving tools (to bring out jin and live veins)
• Bonsai tweezers (for cleaning out old needles)

Frequently asked questions about the Juniper

My juniper is turning yellow inside, why?
If it is only the old needles near the trunk, it is normal natural renewal. If the yellowing spreads to the outer tips, it is a serious problem (red spider mite or root rot).

Can I keep it indoors at Christmas?
Only for Christmas Eve! A juniper indoors dies within a few weeks. It must stay outside.

Why shouldn't I use scissors on the foliage?
Because by cutting the scales in half, the cut part dies back and turns brown. Pinching by hand separates the scales at their natural joint, leaving the tip green and healthy.