Japanese Maple ‘Osakazuki’ · Acer palmatum ‘Osakazuki’

The cultivar distinguishes itself operationally from the dissectum forms and purple-leaved selections on three points: a robust seven-lobed palmate leaf without thread-like cutting; a vase-shaped habit in youth that broadens with age to 4 to 6 m in height by 4 to 5 m in spread; and improved sun tolerance compared with the laceleaf forms, which reduces the strict half-shade requirement that conditions specification of most Japanese maples. The role in a European plant schedule is the standard Acer palmatum feature position in domestic and intimate-park settings, with autumn colour as the specification driver.

Climate envelope: hardy to approximately minus 18 degrees Celsius (USDA zone 7a), reliable across zone 8 and warmer; reported successful in sheltered zone 7b sites across the Atlantic seaboard, the Po valley, central France, the cool-temperate uplands of the Balkans and Carpathians, southern England and Ireland, and milder parts of the Baltic Sea littoral. Not recommended for prolonged continental bare-ground frost below minus 20 degrees Celsius in open sites east of central Germany or in the inland Pannonian basin without shelter; heat tolerance is moderate, with leaf scorch a real risk above sustained 35 degrees Celsius without adequate root moisture and half shade. Annual rainfall above 700 mm distributed through the season is preferred; below 500 mm with summer drought, reliable establishment requires irrigation.

Site requirements: humic, slightly acidic to neutral, evenly moist, well drained substrate; tolerates moderate clay where structure prevents prolonged waterlogging; sensitive to compacted urban substrates and de-icing salt, which excludes the cultivar from street alignments (Platanus, Tilia, Gleditsia remain the canon for that role). Wind exposure on the Atlantic coast is tolerated when sheltered from salt-laden gusts. Genus-typical moderate disease and pest profile; no exposure to the major European-wide phytosanitary alerts under EPPO surveillance relevant to Acer (Russrindenkrankheit of Acer pseudoplatanus is genus-specific and does not transfer to A. palmatum); the standard caveat is Verticillium-wilt risk on burdened soils.

Foliage holds a clear bright green through spring and summer, deepening into mid-green in high summer, with fine texture and a discreet sheen. Autumn colour develops between mid-October and mid-November, turning to a luminous scarlet to crimson rated among the most intense within Acer palmatum, and holding two to three weeks before leaf fall. Specified as a feature specimen in domestic gardens, intimate park clearings, courtyard schemes, and Japanese-inspired plantings, where the cultivar's scale (larger than the dissectum forms) gives it the presence to structure a composition without reaching canopy dimensions.