The Koto Hime Japanese maple, Acer palmatum ‘Koto Hime,’ is in the dwarf or yatsubusa group of plants which are prized for bonsai training. This cultivar is best when trained as a shohin or small size bonsai because of the diminutive and tightly congested foliage.
Koto Hime Japanese maple originated in Saitama Prefecture in Japan. The foliage is generally light green and is crinkled along the edges. Of all the maple cultivars Koto Hime Japanese maple has the smallest foliage. In spring the emerging foliage is colorful and appears as blossoms. The autumn color is not dependable for this cultivar, but the foliage generally becomes yellow before dropping in mid-autumn. Cultural practices and the current weather season determine the intensity of autumn coloring.
The leaves of Koto Hime Japanese maple are closely spaced which means that there is an abundance of adventitious vegetative buds, even on old wood. This is an excellent characteristic for drastic pruning thick trunks and branches for developing or remodeling bonsai.
Most maples have an opposite leaf arrangement, but this cultivar often sports and produces a whorled arrangement. I have even seen branches form a fasciated or flattened shape, but it was not stable and worthwhile to propagate.
The most distinctive characteristic of Koto Hime Japanese maple is the extremely upright growth habit which sharply contrasts with Kiyo Hime Japanese maple which grows horizontally. Many of the dwarf maple bonsai in the yatsubusa group tend to have their crowns die back after about 20 years. I have numerous Koto Hime Japanese maples, many over 30 years old and have not seen the crown dyeing. However, I have experienced dyeing crowns on other Japanese maple cultivars.
Koto Hime Japanese maples are extremely easy to root as semi-softwood cuttings. Although cuttings can be taken anytime with good results, the ideal time for rooting is in late spring. Two to four inch terminal semi-softwood cuttings taken in May or placed under mist can be expected to root in approximately two to four weeks. Thick branches also root easy. Like other cultivars of Japanese maples, extra winter protection will produce healthy plants in spring.
Koto Hime Japanese maple can also be air layered with ease. Even large branches over one inch in diameter will root in approximately two months when taken in spring.
Since the natural characteristic of Koto Hime Japanese maple is upright the standing bonsai styles, (formal and informal upright and slanting) are the best forms to use. Any horizontal branching must be trained by wiring or pruning. Even if the branches are wired down, all future growth will remain upright.
Small size bonsai can be developed quicker than larger specimens, especially when air layering sections from large plants. Small specimens need small, neat foliage to be in proportion and this cultivar is perfect for that. The foliage is so small I have not found it necessary to defoliate to reduce the size. Small leaves often are deformed and do not resemble maple foliage.
Since the leaves are so tightly congested, it is necessary to thin out the buds each spring when they swell or as they are opening. This technique will eliminate many of the freely produced buds along thick old trunks and branches and give strength to the desired branches.
Should a branch get damaged, die or pruned, a new bud can easily and quickly be trained as a replacement. Allow the small replacement bud to extend without pinching or training to encourage the development.
Before thinning out in spring
After thinning out in spring
For additional information on Koto Hime Japanese maple and other dwarf cultivar see the 1994/2 issue of International BONSAI.