Easily 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.
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 or 7 but less frequently 9 pointed toothed lobes. Small reddish-purple flowers in umbels bloom in mid spring (April). The flowers are rather attractive close up, but are not particularly showy from a distance. Flowers are followed by samaras (to 3/4" long) in pairs. Samaras ripen in September-October. Fall color includes shades of yellow, red-purple and bronze. Cultivars (often grafted) are quite variable.
‘Omurayama' is a weeping form of Japanese maple. It is not part of the dissectum group (generally low-spreading shrubs). It typically grows in an upright, rounded, cascading form to 8-10' tall over the first ten years, eventually maturing to 10-15' tall and as wide. Young plants are mostly upright. They develop a cascading form with maturity as the slender branches become pendulous near the tips. Palmate leaves (to 3" long) are deeply cut into seven lanceolate lobes each having toothed margins and pointed tips. Foliage emerges light green with orange tinted margins in spring, matures to a rich green in summer and finally turns bright red, orange and gold in fall. Small reddish flowers in spring are somewhat attractive on close inspection, but are not showy from a distance.
No serious insect or disease 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.
Japanese maples are generally grown for their attractive foliage and shape. Specimen/accent or group around the home or yard or patio or periphery of the border or rock garden. Good sun-dappled understory tree. Cascading form can be showcased by planting this cultivar near a pond or water garden.