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Chapter 9. Japanese Zelkova Bonsai from Seedlings*

Sinkichi Kano

How to raise the gray-barked elm from seed and how to train the trees to form miniatures of the naturally grown forest trees

My prime objective in growing zel-kova bonsai is to reproduce the image of Japanese zelkova (Zelkova ser-rata, or Z. keaki) which I have held in mind since early days when I was deeply impressed by these giant trees. Reproduction in miniature of the natural shape and appearance of the old trees is my purpose.

First Year

Sowing. The seed is sown in the spring (late March or early April). Outdoor sowing is satisfactory, but if one wishes to have only thirty to fifty seedlings for bonsai, it is better to sow the seed in a shallow pan, somewhat deeper than the usual growing pans. To provide good drainage, a thin layer of coarse sand is spread on the bottom of the pan, which is then filled to a depth of 2 inches with loamy soil. This is smoothed and pressed lightly on the surface. Place the seeds singly at intervals of 1¼ to 2 inches on the soil, then sift light soil over them until they are covered. After it has been thoroughly watered with a sprinkling can, the pan should be placed under a tree or in some other place shaded from the direct sun; on rainy days it should be moved under a roof. Germination takes three to four weeks.

*For this article on the raising of bonsai from seedlings, I have been very fortunate in having, through my good friend Mr. T. Uchida, the editor of a Japanese fruit-growing magazine, the cooperation of Mr. Senki-chi Kano. Mr. Kano has long devoted his leisure time and interest solely to raising zelkova bonsai from seed. He is now growing some three hundred zelkovas in pans. These are from 14 to 16 years old and were all grown from seed by Mr. Kano. Born and spending his early life in the mountainous country near Mt. Fuji, Mr. Kano was deeply impressed by the grandeur of the giant zelkovas which he saw growing in nature and in home grounds and came to think of zelkova as the king of trees. Moving to the city of Shizuoka some forty years ago, he was struck by the fact that zelkova bonsai commanded far higher prices than any other kind. The timber of Japanese zelkova is one of the most highly prized in Japan.

Transplanting. When the seedlings have produced two or three leaves, about the middle of May, they should be transplanted singly to small pots. Care should be taken to shorten the taproot and spread the slender side roots in all directions so that they will be well developed at the surface of the soil. Fertilizer is applied occasionally; I use decayed rape cake steeped in water. (Also see chapter 14)

First training. By August the seedlings will have attained a height of 10 inches or so; this is the time to place a bamboo cane at the side of the trunk for straightening it, tying the trunk to the cane at several places. To insure a straight trunk, the bamboo cane support is needed for three or four years.

Wild seedlings. If mature zelkova trees are accessible, usually one can find 2-to 3-inch seedlings under them in May and June. If straight-trunked ones are selected and carefully dug out so that the roots are not injured, they are good enough to use for raising zelkova bonsai.

Gray-barked elm, or Japanese zelkova bonsai just after leaf thinning and trimming

Second Year

Root training. The next March it is important to take the tree out of the pot, shake off part of the soil, and examine the root. The development of the root is the vital point in zelkova bonsai. If the roots are well developed on all sides and all these roots are balanced in size, the the tree is considered a fine one. Such nice trees are difficult to obtain, and scarcely one in ten seedlings is so formed. In most seedlings the roots are developed on only one or more sides but not all around. Such a seedling can be induced to produce roots on all sides by cutting off a narrow ring of bark (% inch) at the base of the tree where the new root formation is desired, as shown on the next page. The tree is then planted in a deeper pot, the soil covering the roots to a depth of #8541; inch above the removed bark ring. All the branches produced on the trunk are removed as soon as they sprout, since it is desired to keep the trunk clean and straight.

Leaf thinning. In the middle of May leaf thinning is practiced, only one third to one fourth of the total number of leaves being left. After leaf thinning, every shoot should be cut back so that only two or three buds are left. This retards growth and maintains dwarfness. The appearance of the trees after these operations is shown in the accompanying photographs.

Third Year

Root trimming. The trees treated for new root production have roots formed on all sides and at right angles to the trunk, and the old root system is nearly decayed. The old roots under the ring of new ones are cut off and all the new ones are shortened to a length of 2 inches.

One of the above trees two weeks later, with new foliage

Repotting. When the trees are repotted, great care must be taken to arrange the roots as shown in the first sketch on page 87. Unless the roots are arranged like this, the value of a zelkova bonsai is greatly reduced, as the exposed old roots are a primary object of appreciation.

It is essential to use dry soil for repotting, but immediately after repotting, the tree must be thoroughly watered. The pot is filled with water to the edge; when the water sinks away, the pot should once more be filled. While the water is sinking into the soil, the tree should be slightly lifted and shaken. Then the roots will appear exactly as in the second sketch on the next page.

Leaf and shoot trimming. As in the previous year, leaf thinning is practiced. The shoots are trimmed to a good shape and the denser parts thinned out. In trimming, care should be taken not to form the branches as shown in the first four sketches below, but to try to have them as shown in the last sketch.

Fourth Year and Following Years

Repotting and root trimming. Transplanting (to a pot of the same size or larger) should be done in the spring. Thickly grown parts of the root mass are thinned and all roots formed in the last year are shortened. Then the lower side of the root system is clipped

Left, opposite branches; right, one branch immediately above another: both to be avoided in good bonsai

Left: Diagram showing how roots should be arranged and cut when tree is repotted. Right: Arrangement of roots after tree is watered and slightly lifted and shaken.

evenly with scissors to allow potting and growing in shallow pans. The shallower the pans in which the trees are grown, the better. This transplanting and root trimming should be done every spring throughout the coming year. Leaf thinning should be done between the middle of May and late June, and at the same time shoot trimming should also be done.

Unwanted sprouts. At budding time in the spring and after leaf thinning, sprouts appear at unexpected places on the trunk and branches, and these should be rubbed off or cut off. Aphids and other insects are exterminated in the usual ways.

Autumn. After the leaves have fallen, any disproportionate and undesirable twigs and shoots are removed, so as to

Left, branches in a circle; right, branch parallel to trunk: both to be avoided
Branches alternating and spreading—the result to be desired

Winter appearance of a properly trimmed Japanese zelkova bonsai

enhance the symmetrical and delicate beauty of fine twigs and shoots which produce the atmosphere and image of a great tree throughout the winter, as shown in the accompanying photograph. In the spring, just before the buds burst, for the sake of possible improvement in the beautiful shape of the tree, twigs and shoots are cut back as short as possible. Then the renewing and rewarding beauty of the young leaves is awaited.

General Care

For potting soil for zelkova bonsai I use loamy soil from cultivated land or sandy loam from the mountains. The soil is sifted through a sieve ( #8539;-inch mesh), and used only after it has been well and thoroughly dried. The tree should be planted in the dry soil in the pan, and the pan shaken several times after planting. The surface of the soil is then leveled and immediately watered gently and thoroughly with a watering can. The soil should never be pressed.

Surface roots. When a zelkova bonsai becomes older, several roots become thick and appear at the surface of the soil. Such a "root-surfa'ced-on-the-soil" tree is much sought after and very ornamental. (See chapter 2) However, if the roots are surfaced when the tree is young, they never thicken; only roots in the soil will do so. After learning by bitter experience, I cover surfaced roots slightly with soil, and on this place moss. As the roots develop, the moss becomes scanty and the roots gradually appear on the surface. The trees in the photographs are 14 to 15 years old and the roots are not yet developed sufficiently to appear on the soil. I have several trees of the same age that do show surfaced roots. Bonsai merchants often show surface-root formations in young trees for commercial reasons, but this is not good for nice root formation on the soil later on.

Shading. In the hottest weather, July and August, the trees are shaded; I use marsh-reed screens.

Watering. Over watering is not good for the trees. However, a zelkova bonsai are grown in shallow pans, they dry out rapidly in the summer, and watering twice a day is necessary; but in other seasons once a day is enough. After the leaves fall in the winter, it is sufficient to give water once every other day.

Training

Materials. For training one should have at hand bamboo cane, string, and wire.

The bamboo cane is split into pieces and each piece is whittled to suitable size for use as a splint for fixing a shoot or a branch in the desired position. The bamboo splints should be tied with string at intervals of an inch or more.

For tying bamboo splints in place, instead of string I prefer the leaves of Yucca recurvifolia, an American desert plant which is now grown here and there in Japan. The leaf is split into thin strips and exposed to the sun for one or two hours; it is then just right for tying. If it becomes old and dry, it can be immersed in water before use. It has the advantage that knots made in it do not work loose as do those in string.

Diagram showing how to change the shape of a fork

If one wishes to narrow a wide fork, the branches should be tied closer together with the yucca leaf. If it is desired to widen the upper part of the fork, a bamboo stick should be placed between the branches, as shown above.

Slender branches trained as described will be well fixed in position in one month or so; thicker ones will take three months.

Copper wire is better than the bamboo for curving branches. A wire of thickness suitable for the branch is selected and coiled around the branch; then the branch is bent to the desired curve. Although easy to use, copper wire will cut into the branch if left on too long a time. Wire should not be left coiled around the branches for more than two months; it is wise to examine it after forty to fifty days.
How to tie a bamboo splint on a branch to hold it straight

Method of coiling copper wire around a branch to hold it in a curve

In growing zelkova bonsai for many years, I have observed many variations in individual trees in the color of young leaves, teeth on the margine of the leaves, and general form. When they are grown in very shallow pans as shown in the photographs, the leaves become smaller and neater.

Raising; zelkova bonsai from seed is very interesting with its growing, thinning, pinching, trimming, and training. No gorgeous colors are produced at any time of the year during the long life of the trees; it is their stature when bare or in full leaf, the aged bark, surfaced roots, and slender, graceful twigs and shoots that charm us so much. Bonsai trees 10 to 20 years old are not yet old enough to give full satisfaction; I think one must wait until they become 50 years old; then at last they are perfect zelkova bonsai.

The author and some of his zelkova bonsai

A black and white illustration fails to reveal the special qualities of the gray bark, clustered bell-like blossoms of spring, and gold and scarlet tinted foliage of autumn, all of which make white enkianthus (Enkianthus perulatus) so desirable as a bonsai. From the Brooklyn Botanic Garden collection, a gift of Mr. and Mrs. Howard Phipps.

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