Japanese Maple ‘Seiryu’ · Acer palmatum ‘Seiryu’

'Seiryu' is the only cultivar within the Dissectum group of Acer palmatum to hold an upright habit. Every other cultivar in the group forms a weeping mound with branches arching toward the ground; this one forms a small upright tree with a vertical, lightly rounded crown reaching 3 to 4.5 metres in height and 2 to 3 metres in spread at maturity. The Japanese name translates as "green dragon", a reference to the ascending silhouette above the finely cut foliage.

Winter hardiness is reliable to approximately -18 degrees Celsius (USDA zone 7a) on sheltered, free-draining sites; damage to one-year wood is observed below -20 degrees Celsius under prolonged barefrost. Reliable performance through Atlantic and warm-temperate Continental Europe, sheltered sites in zone 7b across coastal Netherlands, Belgium, the Po valley, lowland Austria and southern England. Not recommended in open exposure across the Pannonian basin in severe winters, in interior Scandinavia, or above 600 metres in the central and eastern Alps without protection. Tolerates the cooler summer maxima of Atlantic Europe better than the prolonged dry heat of inland southern Europe, where half-shade becomes obligatory.

Growth vigour is unusually strong for a laceleaf maple, closer to a species-form Acer palmatum than to the weeping dissectums. The framework organises itself without the high-stem grafting and annual crown training that pendulous dissectums require; sanitary pruning in late winter is sufficient. Foliage is deeply dissected into narrow filaments, a clear luminous green from leaf-out through late summer, with autumn shift through yellow and orange with red highlights between mid-October and late November.

Site requirements match the species: cool, free-draining, slightly acidic to neutral substrate, with reliable shelter from prolonged afternoon sun in regions with summer maxima above 30 degrees Celsius. Drought tolerance is limited: supplementary irrigation through the first three growing seasons is required, and a maintenance irrigation cycle is advisable during extended summer drought once established. Rainfall above 600 mm distributed through the season suits established trees; the cultivar is not specified for prolonged dry-summer regimes below 500 mm without sustained irrigation. Crown architecture is compact and tolerates confined root volumes well; not specified as a street tree, but suited to courtyard, parterre and large planter contexts.

Use as a focal specimen in walled gardens, courtyard plantings, shaded parterre positions, or as a container subject for protected terraces. It substitutes for a weeping dissectum where the specification calls for an upright silhouette rather than a cascade, or where the horizontal spread of a high-grafted pendulous cultivar exceeds the available footprint.