Fern-leaf Full Moon Maple Has Bold Foliage and Brilliant Fall Colors
One of the loveliest of Japanese maples is not a selection of Acer palmatum (commonly known as Japanese maple), the most popular species. Instead, it’s derived from one of the twenty-three other maple species native to Japan, Acer japonicum. My favorite selection is the bold and showy fern-leaf full moon maple, A. japonicum ‘Aconitifolium’. Our Seattle Japanese Garden has one specimen, planted in 1995 in Area ZZW, along the garden’s west side fence.
Acer japonicum is a sturdy, multi-stemmed deciduous tree native to mountain woodlands on the Japanese islands of Honshu and Hokkaido. It also grows in Manchuria and Korea. In the wild, a height of 45 feet is not unusual, but in cultivation it’s much smaller. The species and its selections (cultivars) have leaves that appear rounded like those of our native vine maple. This rounded outline has given rise to its common name, full moon maple. [A. palmatum, although closely related, has palm-shaped leaves.] Most have leaves that are shallowly divided into nine or eleven lobes, dissected less than half-way to their base. All have reliable fall color in brilliant tones of orange, red & burgundy.
Excellent selections of full moon maple have been developed – although considerably fewer than those of A. palmatum. Acer japonicum ‘Aconitifolium’ was introduced in New York in the late 1800s. It’s smaller-growing than the species, maturing as a round-topped tree about 15-20 feet tall by 10-15 feet wide. With an upright habit and sturdy shoots, it needs very little pruning to maintain its attractive form. ‘Aconitifolium’ is one of the largest-leaved selections and, unusual for the species, has deeply dissected foliage. Its 11-lobed leaves are longer than wide and irregularly dissected, giving it a bold fern-like appearance – hence the common name, fern-leaf full moon maple. The lobes are deeply cut, almost to the leaf base, becoming very narrow in the area closest to the stem (petiole). The cultivar name, ‘Aconitifolium’, derives from another resemblance – to the leaves of Aconitum, a perennial known as monkshood.
In Japan, fern-leaf full moon maple is known as “dancing peacock maple,” (mai kujaku), a reference to its bold and deeply cut, yet delicate foliage. Small but showy deep red flowers emerge in early spring, before the bright green leaves, which age in summer to a deeper green. Like other maples, seeds are contained in winged structures known as samaras. In fall, the leaves turn fiery shades of orange, red, burgundy and purple. As they move in the wind, it’s easy to imagine that they’re dancing peacocks.
Hardy to USDA Zone 6 (minimum temperature -10 degrees F), or perhaps even lower, fern-leaf full moon maple grows best in rich, moist, well-drained soil, in sun or part shade. However, it’s somewhat tolerant of sand and clay. Fall color is best in full sun or open shade. With increasing shade, the colors will be more subtle – orange and yellow with touches of red. Here in the Pacific Northwest, it’s one of the most reliable trees to develop fall color.
If you’re interested in buying this beautiful small tree for your own garden, you’ll generally find it offered under the name ‘Aconitifolium’. Historically, however, it’s been known by numerous other names: ‘Hau hiwa’, ‘Hey hachii’, ‘Laciniatum’, ‘Palmatifidum’, ‘Parsonii’, ‘Veitchii’, and ‘Filicifolium’. The latter was originally considered a distinct selection, but now is viewed as simply another synonym for ‘Aconitifolium’.
Despite its large and boldly dissected foliage, A. japonicum ‘Aconitifolium’ is not a coarse-looking tree. Especially in autumn, we experience it as delicate as well as bold. In the gardens of Japan, and in our own, the fall transformation of this special tree is an important signal of the changing of the seasons and the transience of all things.
Corinne Kennedy is a Garden Guide, a frequent contributor to the Seattle Japanese Garden blog, and retired garden designer.