Spruce

Spruce occupies a strange position in bonsai. Wild spruces are among the most iconic trees of northern landscapes — forming the boreal forests of Scandinavia, Canada, and Siberia — and the species' aesthetic appeal as a "mountain tree" form is obvious. Yet spruces are notably under-developed as bonsai compared to pines and junipers, partly because the species' growth pattern doesn't respond to the well-established pine techniques (decandling doesn't work), and partly because Japanese bonsai tradition has favoured other conifers.

This means there's less established literature and fewer techniques to follow for spruce than for pines. The flip side is that the species is hardy across the entire UK, including Scotland and exposed northern positions, where Japanese black pine genuinely struggles. For UK growers in cooler regions, spruce is a legitimately useful conifer.

Several species sit under 'spruce' for bonsai purposes. Picea abies (Norway spruce) is widely planted in UK and most accessible as nursery stock. Picea glauca (white spruce, particularly the dwarf 'Conica' form) is sometimes used. Picea jezoensis (Yezo spruce, from northern Japan and Russia) is the spruce most developed in Japanese bonsai. Picea sitchensis (Sitka spruce) is widely planted in Scottish forestry and collected mountain specimens can produce dramatic bonsai. Picea abies 'Nidiformis' (bird's nest spruce) is a dwarf cultivar suited to shohin work.

The species is more refined-foliage than pines but less so than Hinoki cypress or yew. Needles are sharp — handling spruce involves more discomfort than handling cypress.

Water when the surface of the substrate has dried. Typically every 2–3 days in summer, every 4–7 days in spring and autumn, every 7–14 days in winter.

Spruce is moderately drought-tolerant compared to deciduous species but less so than junipers. The species likes consistent moisture during active growth without saturation.

Avoid overhead watering in damp conditions where airflow is limited; wet foliage encourages needle cast and other fungal issues.

Tap water of any hardness is fine.

Light feeding. Half-strength liquid feed every two weeks from May through to mid-September. Slow-release organic pellets in spring and early summer.

Heavy feeding produces long needles and weak branches. Spruce responds to restrained feeding better than vigorous regimes.

Stop feeding by mid-September.

Very free-draining, slightly acidic to neutral. Spruce demands drainage like pines.

Repot every 4–6 years on established trees. The window is late March to early May — wait for visible root activity.

Spruce tolerates root work less well than yew but slightly better than Japanese white pine. Mycorrhizal preservation matters. Don't bare-root. Remove no more than a quarter of the root mass on healthy trees.

The species recovers reasonably from root work but pushes weak growth the season following major repotting.

Spruce pruning differs from pine pruning. Decandling doesn't work — removing all new growth shoots can severely weaken or kill the tree.

The technique is pinching, similar to junipers and cedars. In spring as new shoots elongate, pinch out the soft tips between thumb and finger before needles harden. Pinch in waves through the tree, strongest growth first. Don't use scissors on living growth — cut needles brown at the cut.

Through summer, leave foliage undisturbed. Late summer or autumn — selective thinning of overly strong areas. Cut back individual shoots to woody portions where back-budding is possible.

Structural pruning in autumn or winter (October–February). Major cuts heal slowly. The species back-buds from old wood reluctantly — plan major reductions carefully.

Needle thinning in autumn (September–October): selectively remove old needles to balance energy and let light into interior. More needles on weak branches; fewer on strong.

Wire from autumn through to early spring on dormant trees. Spruce bark is moderately resistant to marking. Use copper for structural branches and aluminium for finer work. Wood is moderately flexible — major bends need raffia wrapping.

Branches set well after wire removal. Wire usually stays on for one to two growing seasons. The slow growth means wire monitoring can be less frequent than on vigorous species.

Informal upright is the natural fit. Literati works well — spruce's natural high-altitude form (single tall trunk with crown foliage) translates directly into the literati aesthetic. Cascade and semi-cascade work on suitable material. Twin-trunk and forest plantings are particularly fine — spruce forests are the natural form in the wild and miniature representations are striking.

Formal upright doesn't suit the species. The natural habit produces irregular branching that fights the formal upright structure.

Hardy across the entire UK including the most exposed Scottish positions. Spruce is the conifer most adapted to extreme cold among common bonsai species — Picea abies and P. glauca survive temperatures below -40°C in their native range and shrug off any British winter.

The main winter consideration is excess moisture rather than cold. Tilt pots for drainage. Position out of standing water during prolonged wet weather.

Never bring indoors.

From seed (autumn-sown, cold-stratified) — reliable but slow. Cuttings difficult and rarely used. Air layering possible but unreliable. Most UK spruce bonsai material starts as young nursery stock from garden centres (particularly the dwarf cultivars), as collected upland material (Scottish forestry plantings provide opportunities), or imported as Yezo spruce from Japan.

Generally healthy in UK conditions. The species' wide distribution in UK forestry means common pests and diseases are well-known.