Culture
Best grown in moist, organically rich, slightly acidic, well-drained soils in full sun to part shade. Grows well in sandy loams. May be grown in full sun in the northern parts of its growing range, but prefers some part afternoon shade in the southern parts (including St. Louis) of its growing range. New foliage may scorch in full sun locations in hot summers areas, particularly if soils are not kept consistently moist. Mulch helps retain soil moisture and keep roots cool. Avoid hot and dry sites. Site in locations protected from strong winds. Pruning is best kept to a minimum, but if needed should be done in late fall to mid winter. Spring or summer pruning often results in significant bleeding.
Noteworthy Characteristics
Acer palmatum, commonly called Japanese Maple, is a deciduous shrub or small tree that typically grows to 10-25' (infrequently to 40') tall. It is native to Japan, Korea and China. General plant form is rounded to broad-rounded, often with low branching. Each palmate green leaf (2-5" long) has 5 to 7 but less frequently 9 toothed lobes. Small reddish-purple flowers in umbels bloom in spring (April) followed by winged samaras in pairs which ripen in September-October. Fall color includes an often spectacular combination of shades of yellow, red, purple and bronze.
Var. dissectum is typically a much smaller, rounded, slow-growing shrubby form (often with cascading branching) that rarely matures to more than 12' tall with a larger spread. Palmate leaves, each having 7-11 deeply incised lobes, are deeply cut to the base of the leaf. These dissected-leaf shrubs are commonly called laceleaf Japanese maple, cutleaf Japanese maple or threadleaf Japanese maple. Dissectum means deeply cut in reference to the deeply cut, feathery nature of the leaves.
Genus name is the Latin name for a maple tree.
Specific epithet is in reference to the palmate nature of the leaves. Each leaf has several lobes (typically 5–7) that all originate from one point looking like an open hand with outstretched fingers.
‘Seiryu’ is the exception. It is the only dissected cultivar that has an upright form. Mature plants may grow to as much as 10-15’ tall. Deeply cut and dissected leaves (to 2” long) are smaller than the leaves on most other dissectum cultivars. Leaves emerge light green with reddish tipped edges in spring, mature to medium green in summer and turn gold with orange and red hues in fall. Small reddish-purple flowers in spring are somewhat attractive on close inspection, but are not showy from a distance. Cultivar name means green dragon.
Problems
Potential disease problems include stem canker, leaf spots, fusarium, verticillium wilt, botrytis, anthracnose and root rots. Potential insect pests include aphids, scale, borers and root weevils. Mites may be troublesome. Foliage tends to leaf out early in spring and is subject to damage from late spring frosts. Chlorosis may occur in high pH soils.
Uses
Dissected forms of Japanese maples are generally grown for their attractive foliage and low-spreading shape. Specimen/accent or group around the home or yard or patio or periphery of the border or rock garden. Good sun-dappled understory plant. Dissected foliage and cascading form can be showcased by planting his cultivar near a pond or water garden. Smaller plants can be effective in containers.