Acer palmatum ‘Ukon’ – Japanese Maple for Bonsai

‘Ukon’ is a Japanese maple cultivar that stands out for one thing above all: colour. Not red, not purple, not variegated — Ukon is pure, vivid green. The spring foliage emerges in a fresh, intense, consistent light green that resembles a lemon tree, with subtle yellow tone variations on the newest shoots. As the season progresses, the green deepens to an intense emerald that holds through summer before transitioning to clean yellow in autumn.

Growth is fast and upright with medium internodes and medium-sized leaves. In open ground, Ukon reaches 2 to 4 metres. For bonsai, this vigour supports efficient trunk development — sacrifice branches, directional pruning and free extension all work well. The medium internode spacing offers a good balance between growth speed and structural control, making it more manageable during refinement than cultivars with long internodes like Deshojo or Arakawa.

Bark is smooth throughout, and on young branches it carries a distinctive deep green colour that complements the foliage palette. Like all Japanese maples it greys as the wood matures — welcome ageing in bonsai — but on the young growth you work with most, green bark, green leaves and green presence are what give Ukon its unique character in a collection. Where most Japanese maples are chosen for dramatic colour shifts, Ukon earns its place by being the one that looks alive and fresh regardless of season. For bonsai, informal upright and multi-branch styles at small to medium scale suit it well. Ukon is the green outlier in our range — see the full Acer palmatum cultivar collection.

Cultivation note: Ukon thrives in good light, which keeps the green vivid and intense. In too much shade the foliage can lose its distinctive brightness. Avoid heavy nitrogen feeding — balanced fertilisation maintains the clean green colour without pushing excessively long internodes. The deep green bark of young branches is part of the appeal, so be mindful of wire timing to minimise scarring.