Willow

Willow is the bonsai species that thrives on the opposite of standard bonsai watering advice. Where every other tree in this catalog needs drainage to survive, willow happily sits in saturated substrate, can be grown with its pot standing in a tray of water, and produces vigorous growth in conditions that would rot any other species. This makes willow easy to keep alive but genuinely challenging to refine.

The cultivation challenges are several. Willows grow fast — far faster than any conventional bonsai species — which makes them difficult to keep at scale. They ramify reluctantly, preferring to extend long shoots rather than build dense fine branching. They have soft thin bark that marks visibly from wire. And many willow species produce long pendulous shoots that resist conventional bonsai styling — the natural weeping habit fights upright forms.

For UK growers, two willow species/cultivars are most suitable for bonsai:

Salix integra 'Hakuro-nishiki' (dappled willow) — variegated cultivar with cream-pink-green foliage, more compact than most willows, naturally suitable for bonsai scale. Widely available in UK garden centres. The standard choice for willow bonsai.

Salix babylonica (weeping willow) — the classic large weeping willow, suitable only for cascade-style bonsai given its growth habit. Spectacular when developed but requires significant material to start with.

For new bonsai growers attracted to willow: try Hakuro-nishiki specifically rather than collected willow material. The cultivar's more controlled habit makes it dramatically easier than wild forms.

Heavy and frequent. Willow can be watered daily or even twice daily in summer without issue. The species genuinely loves water and tolerates conditions that would kill any other bonsai.

Many willow growers keep their trees in trays of standing water during summer — the substrate stays moist constantly and willow thrives. This is the only common bonsai species for which this is acceptable.

In winter while dormant, reduce watering but never let the substrate dry completely.

Tap water of any hardness is fine.

Weekly liquid feed from late April through to mid-September. Slow-release organic pellets in spring and early summer.

Willow is vigorous and responds dramatically to feeding. The challenge isn't insufficient feeding but rather managing vigour — heavy feeding produces enormous extension that's difficult to control.

Restrained feeding actually suits refined willow bonsai better than aggressive regimes.

Moisture-retentive rather than free-draining — the opposite of most bonsai species. Willow accepts standard substrates but can also be grown in heavier mixes.

Repot every 1–2 years — willow's vigour fills pots faster than most species. The window is mid-February through to early April. Repot as buds swell.

Willow tolerates aggressive root work — up to half the root mass or more on healthy trees. The species recovers very fast and rarely sulks after repotting.

After repotting, water heavily and continue normal moisture-loving regime. Don't worry about overwatering willow.

Willow pruning is a matter of managing rather than encouraging growth. The species' vigour means standard "let shoots extend and cut back" approaches produce trees with long internodes and weak ramification.

Through the growing season, pinch new shoots back aggressively — every two weeks or even weekly, after just 2–3 leaves have extended. This is more frequent than for any other species in this catalog.

Structural pruning in late winter (February–March). The species back-buds reliably on old wood and tolerates dramatic cutbacks. Trunk chops work well and produce vigorous response — useful for restarting overgrown specimens.

Defoliation works on healthy trees and helps manage leaf size, but isn't essential given how easy willow is to grow generally.

The species' natural pendulous growth on weeping cultivars means wire is often used to position branches against gravity. Major shoots will simply continue weeping downward if not actively managed.

Wire after new growth hardens in early summer or on bare branches in winter. Willow bark is thin and marks easily — apply very loosely and check weekly during active growth. Aluminium for almost all work.

The species' fast growth means wire bites in dramatically faster than on slower species — sometimes within a single month during summer. Many willow growers avoid wire entirely on refined specimens and rely on directional pruning, accepting the limitations this places on styling.

Cascade and semi-cascade are the natural fits for willow, particularly for weeping cultivars. The species' pendulous habit suggests these styles directly.

For non-weeping cultivars like Hakuro-nishiki, informal upright and clump styles work well. The variegated foliage is a major aesthetic feature.

Formal upright and broom styles fight the species' habit. Forest plantings work but require constant management of vigour.

Fully hardy across the UK. Most Salix species shrug off any British winter — the genus is famously cold-hardy.

The main winter consideration is moisture management — willow likes wet feet but saturated cold roots can rot if drainage is absolutely blocked. Standing water is fine if it can drain through eventually.

Never bring indoors.

Trivially easy from cuttings — willow's legendary regenerative capacity means almost any pruned shoot will root if pushed into damp substrate. Hardwood cuttings in winter, semi-hardwood in summer, both work. Air layering essentially happens by accident on suitable conditions. From seed possible but rarely used given how easy cuttings are.

Generally healthy but with several species-specific issues.