3

POTTING AND REPOTTING

BONSAI EXIST ONLY IN POTS; IT is a combination of training and the confining action of the pot that makes the bonsai. The training of a sapling cannot begin until it is put into a pot, and the healthy condition of all dwarf trees depends to a great extent on the way in which the earth in the pots is changed and the roots pruned. A healthy bonsai puts out new roots every year and these roots make it increasingly difficult for water and air to penetrate the soil The surface roots will get all the nourishment and the main root near the trunk will harden and atrophy. It is therefore periodically necessary to cut back the main root and thin out the surface roots.

How often this is done depends on the tree's rate of growth. Evergreens, such as pines and spruces, require repotting only once in from three to five years; broad-leaved evergreens, such as the camellia and the laurel, and deciduous trees, once every two or three years; flowering trees and fruit trees, every second year, but when the blossom or crop is very heavy it may be necessary to repot after a year; willows and crape myrtle, which are very quick growing, twice a year. It should be remembered that these intervals apply to healthy trees which have received proper care.

The best season for repotting is in the early spring when the first new buds appear. A secondary season occurs in late summer or early autumn when for a short time the roots check their growth before the final autumn shooting. Fruit trees such as plum and apricot, which flower before the leaves appear, should be repotted after flowering, but before the leaves open. Fruit trees such as the cherry and apple, which flower in late spring, should be repotted before flowering. A bonsai must never be repotted in winter. In cold weather the tree is in a dormant state and therefore unable to establish itself in the new soil and put out new roots. It is equally dangerous to repot in late spring and early summer when the leaves are fully open but still tender.

If it is absolutely essential to repot in an off-season, say because the pot has been broken or the soil is in dangerously poor condition, the leaves of deciduous trees must all be cut off first, unless it is late in August, by which time they may be left on without ill effects. When a pine tree requires such an emergency repotting, the new, soft needles should be pulled off, leaving the old ones.

SOILS

The soils used in potting bonsai may be classified according to texture and type, different mixtures being used for the bottom, the main, and the top layers in any one pot. The appropriate textures are determined by the size of the pot, while the appropriate types are determined by two factors: the species of tree and whether the tree is still being trained or its training has been completed. These different requirements will be set forth in tables which follow, but first a few general observations are needed.

The soils used in Japan are much the same types as those found in any temperate climate. They should be collected at a depth of about three feet below the surface of the ground, to avoid contamination and insects, and should be spread out and dried in the sun for about a week before sieving. All soils should be sieved and separated, being placed in separate boxes according to type and texture. Powdery soil prevents good drainage and, except in cases where powdered black loam is specifically mentioned, should never be used. The mixtures indicated are those used in Japan, that is to say in a moderate climate with a tendency toward dampness. In a dry, hot climate the mixture should be varied by replacing the specified amount of sand with a similar amount of a mixture of heavy clay, leaf mould, and sphagnum moss in equal parts, as this will hold moisture; if sphagnum moss is unavailable, then use equal parts of clay and leaf mould only. In a climate cooler than Japan's there is no need to alter the basic mixtures given below.

The following tables should answer most practical needs so far as bonsai soils are concerned (see also Fig. 19). More precise, technical information may be found in the soil analyses given in Appendix 2.

TABLE OF SOIL TEXTURES

TABLE OF TEXTURES USED IN DIFFERENT POTS

Note: Where more than one texture is indicated, the coarser should predominate.

TABLE OF SOIL TYPES

TABLE OF TYPES USED IN DIFFERENT MIXTURES

Note: Letters designate the type of soil; numerals indicate the percentage to be used.

METHODS

1 Cleansing (Fig. 17 & Plates 28-32). Before this operation is begun, the old soil should be allowed to dry slightly-but not too much otherwise the tree will suffer-so that it comes away easily from the sides of the pot and from the roots. It should be noted that when loosening the soil with a chopstick (any strong, slender stick with a point will do) the stroke must always follow the direction in which the roots grow, that is to say from the trunk outwards and downwards. First Step. Any moss on the surface of the old soil is removed with tweezers and set aside on a board for future use. The tree is then eased out of the pot together with its soil, which can be loosened from the sides if necessary, and placed on a revolving table. Second Step. A mark is drawn on the surface of the soil so that one-third of the surface is inside the mark, round the trunk of the tree, and two-thirds are outside the mark. If a new and different-sized pot is to be used, this mark should be drawn in such a way that the area inside the mark represents one-third of the surface area of the new pot. All soil outside the mark is removed by jabbing a chopstick into the hard-packed soil, beginning at the surface and working downwards to the bottom. If the soil is very hard indeed, it may be necessary to use an iron bar to remove the outer crust, but this should be done with great care and in such a way as not to injure the roots. Third Step. From the one-third of the original soil which remains, one-half is now removed, this time by calculating the depth of the soil, dividing it in two and removing the lower half. Fourth Step. The remaining ball of soil round the roots is now further thinned out as follows: looking down on the surface of the soil, as if it were the crust of a pie divided into slices by the roots radiating out from the trunk and showing above the surface, the gardener removes every second slice of earth. Such soil as remains after this final treatment is left round the roots until the next repotting. This step is essential when the soil is old and hard but will, in fact, prove beneficial in all cases.

2. Root Trimming (Figs. 17, 18 & Plates 33, 34). Surface roots are never cut straight across but always on a slant. If the tree is healthy, long roots will hang down from it when the cleansing is completed. The main lateral roots are cut back by about a third, that is to say, the length of root finally showing beyond the nucleus of old soil should be roughly the same as the length between the trunk and the outer edge of the nucleus. The bottom roots below the trunk and main roots are usually cut very short, close to the old soil, but in the case of an evergreen needle tree they are left somewhat larger. If a heavy taproot is found, it should be cut off as close to the trunk as possible, provided the tree is in a condition to stand such treatment. If in an unhealthy state, the taproot must be pruned back gradually over a number of years as in the making of a bonsai from a naturally stunted tree (see Chapter 2).

Fig. 17.- Removing old soil and trimming roots. A) Before beginning. 1) Lines mark two-thirds of old soil to be removed in 2nd Step of cleansing. 2) Lines mark one-third of lateral roots to be trimmed away. 3) Lines mark one-half of old soil to be removed in 3rd Step, and, in the case of deciduous trees only, of bottom roots to be trimmed away. 4) Line marks bottom roots to be trimmed from evergreen needle trees. B) After finishing. 51 Remaining nucleus of old soil. 6) Alternating slices of old soil removed this potting in 4th Step. 7) Slices to be removed next potting.

3. Potting (Fig. 19 & Plates 30, 35-41). Meanwhile the pot and its new soil will have been prepared. The pot is thoroughly cleaned and its drainage hole or holes covered with a porous material. If coconut fiber is used for this purpose, it should be stretched a little to make it sufficiently porous. The bottom of the pot is covered with a layer of bottom soil as shown in Fig. 19. Onto this, main soil is sprinkled until the pot is about three-quarters full, care being taken not to mix the soils. If the tree has a poor root development so that there will be a wide area of empty pot around it, it is as well to bank up the bottom soil around the inside of the pot, leaving a pocket in the center for the main soil. If the roots have been diseased or are in poor condition so that below the trunk and main roots there is a hollow, a little heap of main soil should be made at the place where the tree will stand. If the root development or the top-heavy shape of the tree prevents it from standing upright in the pot by itself, wires are prepared at this point with which to wire it to the pot.

Fig. 18.- Trimming surface roots. 1) Copper hoops. 2) Correct trimming angle. 3) Wrong trimming angle.

After the roots have been pruned and the pot prepared, the tree is set in the pot. If the pot is oval or oblong, the tree should be placed slightly off-center, about one-third of the way from one end of the pot. If the pot is round or square, the tree is usually placed in the middle. The tree now rests upon a bed of main soil and should be gently worked a little way into the soil. The pot is then filled to the brim with main soil, which is sifted round the trunk with a small scoop. The tree must be held firmly in place. If it has a handsome, rough bark, great care must be taken not to damage this. Holding the tree with one hand, the gardener gently prods with a chopstick between the roots so that the new soil can penetrate. This is done to eliminate air pockets under the soil, which are potential breeding places for rot. The prodding must be continued with gentle, firm strokes until no further holes appear between the roots. As long as holes continue to appear, they are filled up with new main soil, which is firmly jabbed down. When the tree is solidly established in the new earth, the excess main soil is brushed away; leaving about a quarter of an inch of the rim of the pot exposed to allow room for watering. Any roots showing above the surface should be pressed back with a chopstick and the earth smoothed over them. If these roots are large and stubborn they must be pinned down with a small hoop of copper wire shaped like a hairpin (see Fig. 18). When small, fine roots persist in appearing above the surface, they can be trimmed off. Roots which belong below the earth must not he confused with the roots springing from the base of the trunk. The latter can he left exposed and greatly increase the beauty of the tree.

Fig. 19.- Potting, finishing, and fixing in pot. A) Centered tree in tall pot. 1) Bamboo sticks. 2) Copper wires. 3) Bottom soils. 4) Main soil. Although not shown, the main soil is worked well into the ball of roots to press firmly against the smaller ball of old soil. 5) Topsoil. 6) Dry moss. 7) Space of one-fourth to one-half inch for watering. B) Off-center tree in shallow pot. C) Alternate method of wiring B in the pot.

4. Finishing (Fig. 19 & Plates 42-44). The smooth surface of main soil is now covered with a thin layer of topsoil, the merest dusting, which is spread evenly with a soft brush. This fine topsoil prevents the more porous main soil from being washed away by heavy rain or blown away by wind; it also encourages the growth of moss. The topsoil is sprinkled with dried, powdered moss, which is pressed into the surface with a flat trowel; this will encourage the growth of the moss which is so important in preventing the washing away of soil.

5. Fixing in Pot (Fig. 19 & Plates 36, 46). When a bonsai has been newly re-potted it is often found to he unsteady in the pot, moving if touched. This is unavoidable in the case of trees which lean heavily to one side. It can, however, he circumvented by tying the tree into the pot and this is, in fact, to be recommended for all large trees. These wires are left in place for about six months.

When the bonsai to he repotted is one already well established in a pot, that is to say, a tree which has been in a pot for some four or five years, it will have formed a close mat of fine roots. These roots and the earth with them make a firm base for the trunk, and when the excess earth and roots have been removed, the tree can he secured firmly in place by wires passed through the drainage holes of the pot (which in this case are best covered with coconut fiber) and across the ball of roots. If the pot has only one drainage hole, the wire can be looped round a stick across the hole underneath the pot. This method of holding the bonsai in place is excellent as the wires are almost entirely concealed, but when the tree is in poor condition or is being potted for the first time this support is not sufficient. In such cases wires must be passed under the pot, after potting is completed, and attached someway up the trunk, preferably at a fork. A wire is best passed round the rim of the pot to hold the others in place.

STEPS IN REPOTTING

Plate 28. Using on iron hook to loosen the old soil from the edges of the pot.

Plate 29. Using a chopstick to complete the loosening.

Plate 30. Putting in the main soil. Previously the drainage holes have been covered with coconut fiber, two copper Wires have been threaded through the holes to be used to fix the tree in the pot, and the bottom soil has been put in.

Plate 31. Loosening the outside roots with the iron hook.

Plate 32. Removing two-thirds of the old soil with a chopstick.

Plate 33. Trimming the roots with Sharp scissors.

Plate 34. Root-trimming finished.

Plate 35. Inserting the tree in the pot.

Plate 36. Fixing the tree in the pot with the wires.

Plate 37. Putting in more main soil.

Plate 38. Working the soil down around the roots by prodding with a chopstick.

Plate 39. Brushing away excess main soil.

Plate 40. Pressing surface roots' back into the soil.

Plate 41. Trimming back into the soil the fine roots which still show on surface.

Plate 42. Spreading a paper-thin layer of top soil.

Plate 43. Sprinkling dried, powdered moss over surface.

Plate 44. Pressing the powdered moss into the soil with a trowel.

Plate 45. Watering the tree from above and below.

Plate 46. Method of tying a small tree in a pot with exterior strings.

Plate 47. Transplanting seedlings at 6 mos. Left-hand group: black pine. Right-hand group: mountain maple. Each group shows: 1) a seedling just as it comes from the earth, 2) a seedling with its primary root trimmed back (in an actual case neither so much soil nor so many of the hair roots would be removed as shown here), and 31 a potted seedling.

6. Watering (Plate 45). A large container is prepared beforehand in which the water is sufficiently deep to cover the pot almost to the rim when it is placed in it. A garden trough or old sink is suitable; a baby's bath or large washtub with a flat bottom will also do. It is very important that the water should be either well or rain water; if tap water is used, it must be drawn and left standing in the open air for at least three or four days. The newly potted bonsai is placed in the water to soak. At the same time the tree is watered with a fine-spray can, care being taken to wet all the leaves, but not to wash out the soil. The best way to do this is to wave the can up and down so that the water falls like rain without being concentrated in one place. The pot should be left standing in the trough for several minutes.

7. Aftercare. When a bonsai has been repotted it requires special attention. An evergreen or a tree in leaf should be kept for about a week in a shady place protected from wind and rain. Wind and sun will not harm a leafless tree, but shelter should be given during rain lest the soil be washed away. The tree is watered about three times in the first week. If, however, the earth round the trunk looks dry, this spot is watered with a syringe spray. If the tree is in poor condition, the area round the trunk is covered preferably with wet sphagnum moss, or with a pad of hessian or wood shavings. The moss must not be left in place for more than three weeks as roots may start to form in it. A bonsai should never be manured until one month after repotting. If the season permits, it should not be manured for three months.

8. Transplanting Seedlings (Plate 47). A seedling may be transplanted when it has put out three or four new leaves. At the same time the taproot is cut short, leaving five or six small side-roots at the base of the stem. If the seedling is required for a "small" bonsai, that is to say, one less than six inches high, it is put into a three-inch training pot. The tree remains in this pot until it has been given its final shape (see Chapter 4). If the seedling is to become a normal-sized bonsai with a heavy trunk, it is planted out in the ground. It is dug up every year, the roots are pruned in the ordinary way, and it is replanted in a new place. The tree is left in the ground for three or four years, hut during that time it is trained in the same way as a tree in a pot. The roots of seedlings are very tender and should never have the soil removed from them or made firm round them with a stick. If the old soil does not fall away easily it should he washed off. When the tree is repotted, the earth must he settled by either hitting the sides of the pot smartly with the fist or tapping the bottom of the pot lightly against a tabletop or other flat surface without tilting the tree; the pot should never he shaken hack and forth as this might displace the hole cover.

9. Treatment of Cuttings. After about six months a cutting may he repotted, provided the season is suitable, that is to say, neither in winter nor early summer. The roots of a cutting break so easily that great care must he taken when removing the tree from the pot. The best way is to remove the earth intact from the pot and soak it in water until the soil becomes soft and falls away easily from the roots. If the roots are longer than the depth of the pot, they are cut hack to that length. When a cutting has a naturally attractive shape it can he transplanted straight into a decorative pot; otherwise it should he returned to its training pot. It is repotted in the normal way.

10. Special Conditions Requiring Immediate Repotting. There are various conditions which require immediate repotting, regardless of the season. These are: (a) Pests; when worms or ants are found in the soil and spraying fails to eradicate them. (b) Poor soil; when the soil is either too coarse, so that it forms hard lumps, or too fine and dusty. (c) Damaged roots; when the upper, surface roots are killed by the application of overstrong manure, by manuring too soon after repotting, by water logged soil due to overwatering, or by parched soil due to neglected watering; in these cases the dead roots must be cut away until living wood is found. Special measures to be taken in such emergency repottings have already been described (see page 48).

Color Plate 8. Japanese wisteria. Semicascade style. 3' wide. About 25 yrs. Produced by grafting and potted about 15 yrs. ago. Glazed Japanese pot. Tended for the past 5 yrs. by Mr. Frank Judson.

Color Plate 9. Nagasaki crab-apple. Informal upright style. 1'10".25 yrs. Produced by cleft grafting. Glazed Chinese pot. Produces small yellow fruit in the autumn.

Color Plate 10. Common Ezo spruce, dwarf garden variety "Yatsubusa." Clinging-to-a-rock style. 1' About 15 yrs. Produced from a cutting and planted on rock about 5 yrs. ago. Glazed Chinese container.

Color Plate 11. Japanese black pine. Formal upright style. 2'9". About 80 yrs. Produced from a naturally stunted tree and potted about 50 yrs. ago. Unglazed Chinese pot. Black pine is one of the best species for the formal style; this is a particularly fine example.

11. Repotting after Drastic Pruning. If it is decided to alter the shape of a deciduous tree by pruning away part of the branches or by removing one large disfiguring branch, the bonsai must be re-potted immediately after the operation. It is essential to clear the roots completely of old soil and this is best done by washing them with a hose, a quicker and safer method than cleansing them with a stick.