The Juniper Bonsai: The Essence of Tenacity

When we think of a Japanese bonsai tree, the image is almost always that of a Juniper(Juniperus) with its sinuous curves and the dramatic contrast between the red live vein and white dry wood (Jin and Shari). It is an extremely long-lived and flexible conifer, beloved by masters for the ability to create complex and sculptural forms. The most commonly used varieties are Juniperus Chinensis (var. Itoigawa or Shimpaku) for soft scaled foliage, and Rigida for needled foliage.

Origin & species

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

Exposure and Microclimate

Juniper should live outside, year-round.
It likes full sun, which serves to keep the vegetation compact and prevent fungal attacks. Only in midsummer, in scorching Mediterranean climates, light afternoon shade protects the bright green color, but is not strictly necessary if well watered.

Watering

Unlike broadleaf trees, Juniper does not tell you right away if it is thirsty (it does not droop its leaves), but dries out the branches weeks after damage.
Touch the soil: water only when it is dry. It does not like perennial stagnation. Instead, it very much likes misting on the foliage (even daily in summer, in the evening), which cleans the stomata of dust and moisturizes the scales.

Water quality

Tolerates tap water, but prefers water that is not excessively hard.

Substrate

Drainage is life. Juniper roots need lots of oxygen.

• Recommended mix: 60% Akadama and 40% Kiryuzuna (a Japanese conifer-specific sand that does not flake).
• As an alternative to Kiryu, use excellent Pumice. Avoid pure organic potting soils.

Repotting

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

Fertilization

Fertilize generously in spring and fall with solid organic fertilizer (such as "biogold" or pellets). Suspend in summer and winter. A well-fertilized juniper will have a dark green color and respond better to tillage.

Flowering and fruiting

Produces blue/purple berries (cuddles), 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 color.

Pruning and Stapling (Fundamental!)

Never use scissors to shorten clumps of vegetation! If you cut the scales with scissors, the tips will turn brown and ugly.
Use the stapling technique (with your fingers): grab the clump coming out of the template and gently pull the new tip away, breaking it off at the base. This keeps the antlers compact and green.

Binding & folding

Juniper is the king of binding. Its wood is extremely flexible and can withstand extreme twisting. It can be tied at almost any time, preferably in winter or fall. Use copper wire (or aluminum for beginners) and wet raffia to protect branches during strong bends.

Debarked Wood (Jin and Shari)

Creating debarked wood parts (Jin = dead branch, Shari = debarked trunk) is typical for juniper. Once created and dried, the wood should be treated with Jin Liquid (polysulfide) twice a year to bleach it and preserve it from rot.

Diseases and pests

• Red spider mite: Enemy No. 1. Turns foliage gray/yellowish. Spray often and use acaricides.
• Mealybug: Hides inside dense stands of vegetation.
• Juniper rust: Orange gelatinous outgrowths on branches (caused by proximity to perennials/rosaceae).

Winter & protections

It is a mountain tree. It is not afraid of cold and indeed needs it for rest. In case of exceptional frosts, shelter the pot, but the foliage should feel the winter. In winter the foliage may turn bronze/purple: this is normal protection from the cold; it will turn green again in spring.

Annual calendar

• January-February: Dry wood processing, heavy tying.
• March-April: Repotting (if necessary), starting fertilizer.
• May-June: Steady stapling of vegetation.
• July-August: Red spider mite control, evening showers.
• September-October: Tweezing, fall fertilization.
• November-December: Cleaning old inner needles, liquid jin.

Useful products for this bonsai

• Kiryuzuna (Specific substrate for conifers)
• Jin liquid (For bleaching dry wood)
• Biogold fertilizer (The top for junipers)
• Coppered aluminum wire (For shaping branches)
• Dry woodworking tools (For highlighting Jin and live veins)
• Bonsai tweezers (For cleaning old needles)

Frequently Asked Questions about Juniper

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

Can I keep it indoors at Christmas?
Just for Christmas Eve! Juniper indoors dies in a few weeks. It needs to be outside.

Why should I not use scissors on the vegetation?
Because cutting the scales in half causes the cut part to necrotize and turn brown. Hand stapling separates the scales at the natural joint, leaving the tip green and healthy.