Tuesday, November 2, 2010

Sharpening Straight-bladed Tools

Thecare and sharpening of good bonsai tools is of paramount importance. Dull bladestear plant tissues, making healing difficult. Dirty, rusty blades carrypathogens from tree to tree, spreading what may have been contained otherwise.Tools in poor condition subject you to ridicule and derision and theembarrassment of that look your sensei gives you.

To truly sharpen your flat-bladed tools, I recommend investing in some Japanesewater stones. These come in a variety of sizes and hardnesses. True to theirname, they should be soaked in water for at least ten minutes prior to workingwith them. In the photo above, you may see (from left to right) anadjustable base support, a lap stone, a coarse Japanese water stone (240 grit),a combination stone from Joshua Roth (280/1500), and a combination stone(800/4000). All these items and more are available from Woodcraft. I use four stones in succession, 240, 800, 1500, and 4000. Woodcraft also sells an 8000 gritpolishing stone.

Inorder for your tools to be sharpened effectively, your sharpening stones must be perfectlyflat. The only way to do this is with the lap stone, which is far harder thanyour hardest stone and yet coarse enough to remove the high spots. This stone issoaked, too, and the smaller sharpening stones are passed over it vigorously. Besure to check your surface often to make sure you do not take off too muchmaterial. Once your stones are true, you are ready to begin shaping the surface.

Ifyou have a chipped or broken blade tip, you can reshape it using the side ofyour coarse stone. With the edge up, move the tool back and forth in a straightline, shaping the tip to a good point. This will groove the stone, which is whywe use the edge instead of the surface. Once your point is properly shaped, itis time to proceed to sharpening the tool.

How your tools are shaped

Lookclosely at the blades of a grafting knife (or your better bonsai shears). If youhave a new one, this will be the most instructive. You will find that theseblades are not shaped like your household scissors or any other pair of pruningshears. Where most knife edges are formed where two angled planes meet, agrafting knife edge is formed where a flat (actually slightly concave) facemeets a long, flat, beveled edge. Examine the photograph carefully. You will seea fine line about a quarter inch from the edge of the blade. This is not abeveled edge, it indicates where the layer of better steel is laminated to thebody of the blade. The entire polished face of the blade is a single plane,honed to an edge a few molecules across.

Whereother scissors or shears are designed witha definite bevel at the cuttingedge (to make sharpening easier and to enable the edge to last longer), bonsaishears are designed so that the back face and front face meet at a very acuteangle. Thus a single edge is formed, making possible the sharpest cutting edgepossible. The most important point when sharpening a blade like this is to honethe entire front face of the blade, removing material evenly across the face,providing an edge that is ultimately sharper than a razor. But how does thisinformationtranslate into actually forming that edge?

Making an edge

Thekey to forming a good edge on your flat-bladed tools is in your honing tools andthe proper angle of attack, as it were. As you can see at the right, a shadow isformed if the edge of the blade is held too high. This angle will merely roundoff the back of the blade, and nothing will be accomplished. On the other hand,if the back of the blade is raised, the edge will form a bevel, which will neverbe sharp enough to slice the living tissue of the tree without damaging it. Forthe best results, the face of the blade must be kept in full contact with thesharpening stone throughout the sharpening process. The photo above shows theproper angle for a pair of bonsai shears, while below is incorrect.

Assharpening progresses, a slurry will form, made of material from the sharpeningstone and the blade. It is important that this slurry remain on the stone tofacilitate sharpening of the blade. As the moisture in the stone drops, it iscrucial that it be kept wet. You can add fresh water, but it is easier to keepthe slurry if you reuse the water that has drained from the stone, as it hassome slurry already within it. Always keep your stone wet and your slurry inplace.

Theprocess, once you are comfortable with the position of the tool against thestone, is one of nearly mindless repetition. Many strokes are required toproperly shape a dull blade. One with gouges in the edge may need grindingbefore it can be properly honed. Be careful of your fingertips. I have yet tocut myself on a blade, but I have worn off several fingernails and fingertips bycarelessly rubbing them against the stone. As you make progress, you will wantto move to finer stones until you are satisfied with the sharpness. Ultimately,the goal is to polish the face to a mirror surface. This will ensure the finestedge, making the smoothest cuts, helping the tree to heal itself quickly andeasily.

Pruning Your Bonsai

Pruning determines the basic design of the tree.

“Bonsai must always have a natural shape. The tree should remind the viewerof the growth habits of trees that might be found in nature.
Many years ago when cultivation of bonsai became established in Japan, theclassic styles of bonsai evolved. These styles are not arbitrary or artificial,but they are abstractions and simplifications of the many forms that treesgrowing wild adopt.
Although the shaping of a bonsai does not require that it be a faithful copy ofclassic styles, the precepts involved provide guidance for the basic patternsfor shaping the trunk, relationships of branches and the overallsilhouette.”—Masahiko Kimura

Heavy (Creation) Pruning

Creation pruning is the process of turning an ordinary piece of nursery stockinto a pre-bonsai. It is a very stressful process for the tree, and so shouldonly be done when the tree is dormant, at the end of winter. If it is done toolate in spring, the stress could kill the tree.
For some trees, the process could include reducing the height of the tree bycutting off the trunk just below the final visualized height of the tree. Butfor all trees, it will include removing unwanted or ugly branches. With adeciduous tree, this could include removing up to eighty percent of the tree’sfoliage areas, but for evergreen trees, such drastic pruning can mean certaindeath, so trees may need to be reduced in stages.

Light (Maintenance) Pruning

Light pruning includes thinning of secondary branches, maybe the removal ofsome branch or the restructuring of the apex, and it includes pinching back andleaf removal, or defoliation. It is limited to improving the appearance of thestructure already established by an earlier heavy pruning.
Because it is not so stressful for the tree, thinning of the branches can bedone at the beginning of spring. Pinching back can be done throughout the season(depending on the species), and leaf pruning can be done in summer.

Pruning to Shape the Trunk (Trunk Chop)

Creation pruning on young trees can include cutting back the trunk, sometimesas far as the trunk base (drastic pruning). This is typically done on treesgrown in the ground, in order to create more taper. For some deciduous trees, this canbe done by simply removing the unwanted trunk, cleaning up the cut, and waitingfor new buds to form to choose a new leader. It is usually best to leave an inchor more of stub above the desired new leader to allow for dieback. There is noneed to protect the stub from dying out. This will allow the new leader tobecome strong enough to survive after the cut is cleaned up. These photos showthe technique for cleaning up that stub of a trident maple. Notice that the stubwas sawed off cleanly horizontally. This is done to allow us to use thebest leader from the new buds that erupt. If we cut the tree at an angle, thesap recedes and we have to repeat the process. Pretty soon we can run out oftree!

The size of the trunkscan make it a little more difficult to know just how to proceed. For a very large trunk, a pruning saw can be a great asset. Remember that theJapanese saws cut on the pull stroke, and leave more wood than you think youwill want, so that the cut can be reduced and shaped. Once you have the mainpart of the trunk removed, use concave or spherical knob cutters to reduce thecut. Be careful not to reduce the cut too much, that can be worse than notcutting enough!

When you get the cut to the proper shape, clean up the edges with agrafting knifeor razor blade and seal the cut. I recommend purchasing a good grafting knifeand learning how to sharpen it. Properly sharpened, it cuts far more cleanlythan a razor blade, and the imperative here is not to damage the living tissue.With a grafting knife, thin slices of the extremely hard maple can be shavedoff. Trim this to a gentle, rounded curve that will heal naturally. Do not makethis a concave cut, as it is too large to heal properly and can hold water andpromote rot. Finally protect the cut with a good putty type wound sealer. Thepaste type in a tube is actually grafting sealer and can prevent the cut fromcicatrizing properly.

Pruning to Select the Main Branches

How do we reconcile the notion of a bonsai having a natural shape with thetraditional rules of branch placement? How does first branch, second branch,back branch fit into the ideal of a naturalistic tree?
The first thing to remember is that the “rules” of bonsai style are not rigidlaws written in stone. They are observations about what makes certain treesbeautiful. With that in mind, we can tell that it takes more than just numberedbranches to make a beautiful tree.

Even though every bonsai has a front, it is important to note that the famoustrees have both front and back branches as well as branches at the side. Theseprovide a fullness and balance to any tree. A common mistake is to cut a pieceof nursery stock until one has just a few twigs left at all the “proper” places.This makes for a long time of wondering why the tree looks so bare, if it evensurvives. Remember to leave more branches than you may ultimately use, becausethey can always be removed, but cannot be put back.

Basic Technique for Pruning Branches

Always be sure to use the tool that fits the job you are doing. It is better touse a bigger tool, if the right one is not available. That may mean using a sawto cut a branch, but that is preferable to splitting the bark or breaking yourtool.

Always leave a stub when cutting a branch. If you are going to jin the branch,leave the stub long. If not, leave the stub short. For a pine, it is anexcellent idea to leave the stub for a few months until it stops bleeding, thenreduce it. For deciduous trees, it can be reduced immediately with your knobcutters using several strokes. This prevents splitting of the branch down intothe trunk. For larger cuts, a sharp gouge can do a better job of shaping thecut. After shaping the cut roughly, use your grafting knife to smooth the edgesof the live material--the cleaner the cut, the quicker it will heal.

Once you have the cut flush, hollow it out just a little, and seal the cut.In this photo taken a week after making some larger pruning cuts (vigoroustrident maple), you can already see the edge of the healing wound under the cutputty.

Utilizing Open Spaces

When selecting branches, it is sometimes better to train yourself to see theempty (“negative”) space surrounding them. Often it is easier to see what isholding us back by looking at it in a completely different way.
Not only does a tree take up space; it also has places that don’t. Just as aforest planting should have some open space “to let the birds fly through,” soshould any bonsai make use of both the positive and negative. When the two arebalanced, the whole tree takes on a sense of balance.

Pruning to Shape Branches

Once the main design of the tree has been established, maintenance andrenewal pruning combined with wiring will continue to advance the style of thetree until it is “complete.”
The branches should mirror the trunk. As we select branches at the outside curveof the trunk, we also select sub-branches on the outside curve of the branches.If the trunk has drastic angles or gentle curves, the branches should do thesame. With most deciduous trees, this is accomplished more with pruning thanwiring, although some wiring may be necessary.
To prune to develop branches, you must understand the budding habits of yourtree. Does it bud opposite the branch, or does it alternate? Also, does it tendto die back by one bud, or can you prune it closely to the bud you want? This iswhere specific species knowledge is necessary. Generally, you will want to pruneback to a bud that is growing in the direction you want the new growth to go.You will want to remove any growth downward or straight up, and on trees thatgrow with opposite buds (maples, for example), you will want to prune to justtwo buds at each branching.

Preparing a Tree for Exhibit

The whole of bonsai is this: it is an art with itsultimate end in display. In other words, the whole point of bonsai is todisplay the tree. How can that best be done? What kind of setting actuallyshows a tree to its best advantage? And specifically, what do I need to doto make my tree look its best?

To best illustrate this, let's follow a tree through its preparation forexhibit. For those who have to know, this is not my personal tree, and thisis the only work I have ever participated in on it. This massive Japanese black pine has been grown from a seedlingcutting for bonsai. This is going to be its first public show. I removed all the old needlesto thin the tree slightly, so it's not too dense. All hanging needles havebeen removed so that the bottom of each branch is a smooth plane, as haveany discolored, brown, yellow, or broken needles. Now it's time to choose adisplay pot. This means we are going to repot the tree two days before theshow, because unless we free up the roots, we cannot tell what will be thebest pot for the tree.

Wefollow all the typical procedures for repotting. At top, we are raking thebottom of the root ball to free the roots and trim them short. In the photo above, we are combing the top and sides of to prepare the tree forexactly the right pot.

Above you can see the extent ofthe root work. This tree will remain in its showpot for the nextyear. Had the intent been to put the tree in a show pot andthenremove it later, we would have removed far less root mass and repotted fully after the show. Notice the long roots (below) that still need to bereducedover time, and the guy wires attached to the wood screwdriven betweenplates of bark. Boon has tied a long root to a lowerone to move it into amore acceptable position. He is preparing toremove a portion of the longroot to the left.

The student's assignment is to find several pots ascandidates for the show pot. Here are the choices we provided:

This pot was deemed a bit small, too deep, and not masculine enough. The root pad is sitting on top of 2X4 lumber in the bottom of the pot.

The shape was pretty good, but we thought we could do better with the color. We much preferred a reddish pot with this tree.

We decided that this pot complemented the tree perfectly. Notice how shallow the pot is compared to thegirth of the trunk. Itactually increases the drama of the massivetrunk and shari.

The nebari is improved every time it is worked on, if propertechnique is used. Here it has been adjusted a little more, removing somemore of the longer roots that will have to be reduced in the future anyway,simply to fit it into the pot. Notice how closely it fits. It will be tiedsecurely into the pot with the wires visible in the photo.

Oncethe tree is securely in the pot and the soil incorporated with the roots, itis time to moss the tree. This is not done often enough in the U.S. If youever have the opportunity to look at Kokofu books, you will notice thatevery pot has been carefully mossed.Selected mosses are collected andshaped to fit among the surface roots. If the moss is thin, leave your soilline closer to the rim of the pot, if the soil is thick, leave more room.When shaping the moss, be sure to cut with your scissors to bevel the sidesof the soil and root clinging to the moss. This will cause the moss to moundup naturally when placed. Be careful not to put the pieces of moss too closetogether, as they will tend to push each other up. Small spaces can befilled with very fine dark top-dressing.

Beforeand after photos of moss being applied to a forest planting. Notice in thebefore photo, the New Zealand sphagnum moss that has been shredded andlightly placed over the soil. This helps keep moisture available for themoss and reduce the danger of air pockets drying it out. The end product isvery neat and looks as if it had actually grown there. It is important topiece the moss carefully among the roots to give a natural appearance. Thefinal top-dressing is fine particles of lava.

Just before the show, a soft brush shouldbe used to clean dirt off the pot. Then the pot should be rubbed with walnutoil or canola oil, taking care not to make the pot too shiny. An easy way toapply this is to place walnut meats in the end of an old sock, tape the toeclosed, then smash your nut sock with a hammer until it's all squishy. Theoils will seep through, giving you a good applicator. After rubbing the potwith the oil, rub it again with a clean cloth to remove excess oil.Fingerprints should not show if the pot is touched.

Here you see the final product. Noticethat even in the exhibit, the guy wire is visible. Of course it must be neatand properly attached. Although invisible in the photograph, every branch ofthis tree is wired. The important thing is that the wire is neatly andeffectively done, and is unobtrusive. Very heavy wires and turnbuckles areunacceptable. After the show, remove the moss and replace with top dressingand sphagnum moss for deciduous trees, or black lava for conifers.

This is a bare bones description of theprocess of preparing a tree for exhibit. It does not touch on the extensiveareas of accent plantings, stands, two- versus three-point displays, or manyother areas of exhibiting trees.

Preferred Soil Mix-"Boon mix"

We recommend the soil mix given to us by Boon Manakitivipart. It contains:

1 part lava rock

1 partpumice (which is lighter and holds less water than lava)

1 partakadama (which will break down in about 2 years)

1/2 cup horticulturalcharcoal (per 5 gallon mix)

1/2 cup decomposed granite (per 5gallon mix)

Deciduous trees use a small mix (1/16"-1/4") and add1 part akadama.

Conifers and high mountain species (notablyJapanese white pines), use a medium size mix (5/16"-3/8"). This seems very largeto look at, but prevents these trees from holding too much water. This enablesthe grower to water at the same time as other trees without fear of waterlogging.For appearance, place a final layer of fine mix on top of the soil.

For lower elevation conifer and water loving conifers, use a small mix(1/16"-1/4").

Note: Proper repottingtechnique needs to be applied, otherwise this mix is not recommended.

This root ball has been grown exclusively in this mix and is completelycolonized by mycorrhizae.

Repotting an Established Bonsai

The purpose and necessity ofrepotting bonsai is axiomatic, and need not be repeated here. However, thereis some confusion about the best way to accomplish this crucial task. Inthis article, we will examine in depth every aspect of the repotting of anestablished, older fukien tea bonsai, paying special attention to the properuse of materials and tools to give the best result for both horticulturalpractice and aesthetics. While this is an established, older bonsai, theseprocedures will improve the repotting outcome of any bonsai on which theyare used.

Materials Needed

It seems silly andsimplistic to say it, but the first thing needed for repotting is a tree.The only reason to mention this is to point out that the tree should bestrong and healthy to repot in this manner. If your tree is very weak,repotting can kill it, so be careful! Very few “emergency repottings” reallyare. Better to nurse the tree to better health first.

You will need an appropriatepot for your tree. In this case, we are placing the tree back into itsoriginal pot, so there is no question about the correct one. The followingexample of three different pots for one tree will show a few of theconsiderations in choosing a pot. The size, shape and color of the potshould complement the tree’s style and species. Often, real worldconsiderations slip in and we end up placing the tree in any pot that willfit! While this is not the best solution, it is preferable to forcing a treeinto a pot that is too small. Be sure you have your pot selections readybefore you begin.

Figure2. All three pots in this case are unglazed stoneware, the potof choice for most conifers. This is quite a large tree, sothese pots are sizeable.Thispot’s color provided an excellentcontrast with the barkand foliage.However, it was rejectedfor being too deep, aswell as not “masculine”enough for such arugged tree.

Figure3. This pot had a bit better depth, but the style once againwas a bit too soft, and the color blended far too much with thetrunk.

Figure 4. This seemedthe best fit, since it was simple, elegant,andthe red color reallycomplemented the bark and foliage.Thenebari barely fit intothis pot. The pot is oval, and the roots were touching both front andback of the pot.

Be sure you have plenty ofwire on hand. 2.5mm aluminum is common and easily handled for all but thelargest trees. This will be used to hold the screen in place to cover thedrain holes, and to tie the tree securely into the pot. Smaller aluminumwire is really too soft to be secure except for the smallest of trees. Forvery large trees, especially conifers, annealed copper wire can be used totie the tree into its pot.

There has been somecontroversy in recent years about the necessity of tying the tree into thepot. Rest assured that NOT wiring the tree into the pot is a very recentinnovation. If you repot without securing the tree well, the very nature ofthe bonsai soil will allow the tree to move or even fall out of the pot fromthe slightest wind or movement. Anyone with squirrel problems, or cats, or areal back yard can attest to the problems with a poorly secured tree. Evenif the tree does not come out of the pot, trees thrive better when secured,since the roots do not have to overcome constant movement. Anothercontroversy has come about over the materials used to tie trees in. Somehave called for the use of cotton twine. This is in response to trees badlywired into their pots, damaged because of the neglect. It is far better tolearn the proper way to do things than to find a stopgap so one doesn’t haveto learn the proper way.

Soil screen is anotherimportant component. Much has been said about soil screen, from disregardingit, to insisting that it be imported Japanese screen specifically forbonsai. The job of the soil screen is to prevent soil from leaking out ofthe pot, producing root-killing empty space at the bottom of your bonsaipot. There are a number of products that will accomplish this purpose. Oneof the major suppliers of bonsai tools has a rubberized cloth mesh for sale.We do not recommend this, as it will not hold its shape under the weight ofbonsai soil. One highly recommended product is called “plastic canvas” andis available for about three 8”X11” sheets for a dollar. It is commonly usedto wrap with yarn to make craft projects, and one sheet will suffice for adozen repottings. Some recommend painters’ webbed adhesive joint compoundtape. If the pot is completely clean and dry, I don’t know why this wouldnot work. I have never used it and do not know how well it will hold up inrepotting. Some recommend skipping this item completely for holes less than½ inch in diameter. This seems large to us, since our soil mix is generally3/8 inch or smaller.

A soil sieve will beimportant for making certain your soil drains well, as well as for shreddingyour sphagnum moss to settle on top of the soil. Speaking of soil, becertain you have plenty on hand. Very little is more frustrating thanfinding in the middle of repotting that you lack about a gallon of soil!

Have a component for adrainage layer, slightly larger than your bonsai soil. At the risk of slingsand arrows, “perched” water tables happen in nature, not in bonsai pots!And, since you brought it up, have plenty of water available for wateringyour newly repotted tree.

Finally New Zealand sphagnummoss (white), when shredded through the large screen of your soil sieve,makes an attractive and effective method of retaining moisture in your pot.

Tools Required

In addition to wire cuttersand pliers, root shears, root cutters, and chopsticks (all standardequipment of typical repotting), you should have at the ready a few moreitems. A serrated sickle drawn along the edge of the soil will help removethe tree from the pot. Angled tweezers are far more useful in arranging fineroots at the top and edges than chopsticks. Chopsticks are useful, however,when it is time to incorporate new soil around your freshly repotted tree. Aroot rake, properly used, exposes lower roots for cutting. Soil scoops forfine placement of soil (not shown), a bonsai broom to smooth it, and atrowel to tamp the soil all are important for the aesthetic effect of abeautifully repotted bonsai. It is impossible to place too much emphasis onthe value of a turntable when doing this work.

Handling the Established Bonsai

Proper handling of an olderbonsai is critical to its continued health and beauty. On a rough-barkedspecies, care should be taken never to touch the bark on the trunk or majorbranches where it can be damaged. Some trees, such as azaleas, have verydelicate smooth bark and must also be protected. There are a variety oftechniques available which can help prevent problems. The fukien tea doesnot require as much care in handling.

One of the best ways toavoid difficulties like this is to have a competent and patient assistant.Proper respect for an elder tree demands that it be treated with the utmostcare. Delicate ramification should be protected in the most careful way.Since you will have wired the tree prior to repotting (if the tree was to bewired), be watchful of displacing wired branches. Avoid having to handlewired branches again.

To avoid touching thedelicate bits of the tree, several techniques can be used. When lifting atree from its pot, the lifting can be done from under the “armpit” of thebranches. This will minimize damage done to the tree. Simply freeing thesoil from the pot and pushing up at the joint of branch and trunk can beeffective in removing the tree. Chopsticks can come in very handy here too,especially on heavier trees. Drive the chopsticks deeply into the root massand use them as leverage points to lift the tree.


To prepare the tree forrepotting, it must of course have been cared for well throughout the year.Proper watering, oversight, protection from the harsher elements if needed,and fertilization will give your tree the strength it needs to thrive in thecoming years after repotting.

In the case of moving thetree to a new pot, you should prepare the pot beforehand to receive thetree. Be sure that it is clean, without damage, and large enough for yourtree. Since we are putting the tree back into its same pot, these steps willbe shown after removing the tree, but before doing any root work.

We have the tree ready, andthe pot ready, all our supplies are available and tools clean and prepared.Now, do not forget to prepare the artist. This work should not be rushed—donot attempt this when you are pushed for time. Find the right place for thework. Bright sun, low humidity, and hot, dry, winds are a recipe fordisaster, so a shady spot such as a garage or shaded deck are ideal. Thiswill help you avoid worrying about your roots drying out. Be sure, if youhave friends over to help and advise or learn, that you have plenty of yourfavorite beverage in a cooler at your side. Just be sure you do more of thebeveraging after the work than before!

Remove the Tree from Its Pot

With your assistant holdingthe tree securely, remove all the wires at the bottom of the pot using yourwire cutters. Cut the wire as closely inside the openings as possible(Figure 6), so that nothing is dragging on the roots as the tree comes outof the pot. Cut the tips that hold the screen in place, too, since yourroots will probably be entangled in them somewhat.

Using your sickle (Figure7), and holding the pot securely from the other side, make quick, shallowstrokes until you get to the bottom of the pot. Be sure you keep your freehand away from the cutting edge! The serrated blades on these sickles arevery dangerous. Trying to saw down to the bottom of the pot will bedifficult and damage more roots, while shallow strokes will make the jobeasier and cleaner. Do this on three sides only! It’s best to leaveone side unmolested, so that when we turn the tree on its side, the rootmass will have a secure base to rest on.

Prepare the New Pot

Now it’s time to prepare thepot, since this tree is going back in the same one. Cut your screen to giveplenty of margin on each side, and wire it into the pot. This technique isvery easy and gives good security to the screens if a few simple steps aretaken. To make the wire mesh ties (Figures 8, 9); simply fold a piece ofwire so that you have a very flat “z” or “n”. No need for fancy loops. Makeit large enough so that it extends about ½ inch on each side of the hole inquestion.

When you bend down the tailsto insert into the holes, bend them so that they just go snugly into thewidest part of the hole. This will prevent your mesh from moving side toside. Wrap the tails snugly against the underside of your pot. Another tipfor securing your mesh in the pot is to make the wire tie cross the hole ata right angle to the direction the tree tie-in applies force. This can beseen in the final photograph (Figure 10).

Pre-bend your wire ties sothey lie flat against the bottom of the outside of the pot. Just measurethem against the holes in the pot, bend, and insert from the bottom of thepot into the pot. Forget to do this, and you will find it awkward to addthem after you have a layer of soil in the bottom of the pot! For thistie-down method to work, the portion of the tie wire that will pass over thewide side of the nebari must be longer, and the section that crosses theshort side can be a bit shorter. It is also helpful here, to bend the endsof the wire down over the rim of the pot to hold them out of the way.

Notice that this pot hasdrainage/tie-down holes in the four corners. This is the best configurationfor drainage and for securing the tree in the pot. If your pot has only twoholes, one at each end, pass your tie wires through these holes to tie yourtree in. This arrangement can allow a tree with a less developed nebarimove, so be careful. Pieces of bamboo chopsticks can be passed across thenebari and the wire made to bear on it, giving solid support to weaker ormore delicate areas. For trees with very dense root pads, a chopstick can bedriven into the pad to give a purchase point for the wire.

But what if your bonsai is acollected tree with all its attendant challenges? If you have a wildlydifficult root system, you can use what Boon Manakitivipart calls the“square-root” method of potting. Pieces of dimensional lumber (2X4, 2X6,1X2, etc.) can be cut to proper size to wedge into the pot, allowing a bareportion of the base of the trunk to be supported. Non-reactive screws can bedriven into the base of dead wood, providing another anchor point. Anythingthat secures the tree but does not harm the tree or show above the soil canbe used.

Arrange the Roots

Whileyou are working on your roots, be careful not to cut the remaining wireswith your shears! They can look dark just like roots, and it is not a happycircumstance for the shears. (Figure 11) The photograph shows a drainagescreen with a butterfly-shaped tie. The clip-shaped ties are much easier tomake.

At this point, your rootrake is going to come into very good use. Tip the tree onto the remainingsolid side of the root ball (Figure 12). With a helper holding up the trunkso that the root ball is vertical, stand at the end of the root ball anddrag your root rake across the base of the roots. Hold your rake so that thetines are at right angles to the roots. This will minimize damage to theroots from the tines getting caught behind them.

Use a light stroke; you onlywant to loosen up the first half inch or so. Once you have done this evenlyacross the entire root ball, use your root shears to cut them off as tightlyto the flat surface as you can (Figure 13). Make your surface as flat aspossible! Then repeat the process until you have trimmed the roots as thinlyas you need to. This process can take a while, so work quickly butcarefully.

As your root pad developsover the years, you will find that less and less drastic root work will benecessary. Figure 14 shows a well established Japanese maple being worked.

As you encounter largeroots, when you have determined that they are no longer necessary, removethem flush with the soil using a pair of root cutters (Figure 15). Don’tworry about getting the entire root out at once; expose it a bit at a timeso that you are working all the way across the root ball at the same depth.

How much should you take offof the roots? It all depends on the tree and the condition of the roots asyou go along. Some species or even individual trees will require more thanothers. Figure 16 is an example of a large trident maple properly preparedfor repotting. Only one thing remains to be pruned: the large nut holdingthe tree! Notice the grey areas. This is putty-type cut paste used to coverthe stubs of large roots that have been reduced in this repotting.

When you have your rootsarranged well at the bottom, it is time to work the top and sides of theroots. Until this time, these portions have been untouched to keep the rootball firm and make working on it much easier. The tree in Figure 17 isresting on a turntable, making it difficult to see just how thin the rootball is. It has been reduced to little more than one inch in depth. Infuture repottings, it may be reduced even more.

This tree is well-balanced,but it may well be that your tree will need some sort of support. Manybonsai have a center of gravity outside the base of their roots and cannotsit upright without being held in some way.

Many people use root hooksor chopsticks on this portion of the tree, but both of those items can causea lot of damage to roots. Much easier to control and give a very light touchare the angled tweezers that came with your initial bonsai tool kit (Figure18).

Drag these lightly towardyou, directly away from the trunk. You will find it much easier to arrangethe roots as you like. Don’t be in a hurry to do this. If you are out of thewind and sun, you shouldn’t have to worry too much about the roots dryingout. If they seem to be doing so, drape a wet towel over the half of theroot ball you are not working on, and move it when needed. You certainlydon’t want to get the root ball too wet, as this makes a muddy mess andcauses more problems than it might solve!

Otherroot work should also be done at this time. This tree has a good deal ofdead wood on it, even at the roots. Some of that is reduced with a drawknife(Figure 19) to give the nebari a better, more tapered line, and to get ridof some of the soft, rotted wood. This is an older fukien tea with large,established areas of dead wood. The wood of tropical trees tends to besofter than that of conifers or even deciduous trees, so extra care must betaken to preserve it both for aesthetic reasons and to maintain thestructural integrity of the tree. This tree will eventually need woodhardener or a marine epoxy resin to achieve this.

Following this, it is timefor a little more delicate work underneath the root ball with my tweezers,looking for pockets of bad soil, etc(Figure 20). You should be able to seeclearly the bottom of the trunk at this point. The base of the tree shouldrest solidly on new bonsai soil. Leaving any remnants of bad soil in a rootball is a common mistake of beginners ad experienced enthusiasts alike. Itwill eventually cause your tree to fail, so do not miss any!

Set the Tree in Its New Pot

The next obvious step in theprocess is to secure the tree in its new home. The next few steps arecrucial to making the tree stable and secure, and to ensure that it willthrive.

Drainage Layer/Soil Mound

(Figure 21) TraditionalJapanese bonsai teaching indicates the need for a drainage layer at thebottom of your pot. The deeper the pot, the thicker should be the drainagelayer. Try to use a slightly larger particle for this than your regularsoil, and in a shallower pot, it may only be one or two particles deep. Thiswill help prevent soggy soil and root problems including fungus and rot.

“Perched” Water Tables

There has been somecontroversy as to the efficacy of drainage layers. A great deal has beenmade of the notion of “perched” water tables. A perched water table is

an aquiferthat occurs above the main water table. This occurs when there is animpermeable layer of rock (aquiclude) above the main aquifer but below thesurface. Water percolating down to the main aquifer gets trapped above thissecond impermeable rock layer. [1]

It must be noted here thatperched water tables require a constant supply of ground water and animpermeable layer of rock or clay, neither of which are possible in a bonsaipot.

An engineered sort ofperched water table has been employed by Turf Diagnostics and Design. Thisseems to be the closest thing to what is claimed for bonsai pots:

PerchedWater Table

The USGAsystem provides maximum removal of water during heavy precipitation events,and it stores water above the gravel during periods when the ground is notsaturated.How does it achieve this effect?Because the USGA system isbased upon a concept known as the perched water table, which is also knownas an inverted filter design.It is called an inverted filter because ofthe presence of the fine sand particles over the more coarse gravel.Thisdesign allows water to be held (or perched) in the root zone layer.Thisperched effect occurs because the primary driving force for water movementduring periods of unsaturation is the capillary effect of the particlevoids.

The largevoids of the gravel result in a reduction in the capillary effect.At theroot zone/gravel interface, these larger voids effectively create a barrierto further downward water movement during unsaturated times.As saturationis approached, additional pressure is applied allowing water to move intothe larger voids of the gravel layer, and further down through thesub-surface drainage system.[2]

There are a couple ofinteresting thing about the USGA system. One is that it is engineered toensure that water does perch, as this is beneficial to theplants (sod) above. Another interesting note is that the sod is planted infine sand, and the gravel below is quite large. And while it is not statedin the above reference, my guess is that some sort of filter fabric is usedto keep the two layers distinct.

In the bonsai pot, none ofthese elements pertain. The two layers of soil are in contact, and thedifference in size must not be so extreme. Because there seems to be noproof for a deleterious effect, I choose to follow the Japanese traditionfor its self-evident history of success.

Mound the Soil

The movement of this tree isto the left, so it must be planted toward the right in its pot. A largishmound of soil is placed directly under where the trunk base will sit (Figure22). The tree will be placed here and wriggled firmly into place, removingair pockets or voids underneath it. This mound should not be so large thatthe tree will sit too high in the pot, nor so small that it will allow thetree to sit too low.

Position the Tree

Correct placement of thetree in its pot is a crucial stage of the repotting process (Figure 23).Unless we are restyling an established tree, it should be replaced with thesame orientation it had previously. With a solid nebari and establishedposition such as this tree, it is a fairly simple matter. Position yourselfat eye level with the rim of the pot to check the rise of the nebari fromthe pot. Keep an eye on previously styled branches to be sure they are intheir proper place. Settle the tree and prepare to tie it in.

Bunjin or other trees withunusual planting positions can pose a challenge when trying to repot in anidentical orientation. How does one make certain a return to the originalposition? A small carpenter’s plumb bob is indispensable. Before removingthe tree from its pot, tie it to a prominent branch, allowing the tip toalmost touch the nebari. Place a single dot from a Sharpie at that pointwill help line up the tree correctly in its new pot. Simply be sure that theplumb bob touches the dot in just the same way when repotting the tree.

Wire the Tree into the Pot

Many trees, especially prebonsai, have prominent roots,roots that are too high, or a developing nebari that makes it difficult toget a grip with the wire without damage to the bark. Protect your tree inthis case with a portion of old garden hose cut for the purpose, or someother firm but flexible product to avoid wire scars. Place it carefullybetween the wire and the bark. Be sure it is not going to let the wire slipoff when you tighten the tie wires. One excellent product for this is theused serpentine belt from a late-model car. These have deep grooves runninglengthwise which allow the wire to settle in, avoiding mishaps.

Plan your work here so that your final tie, the onewhich you will tighten in the final step, bears on the portion that wouldtend to tip up if there were no wires present. This will give you your bestholding power. Begin with the wire just to the right or left of that spot(Figure 24), depending on which direction you will be proceeding, and bendthe wire across the nebari, far enough out that it doesn’t rub the bark orshow above the soil. If necessary, a stub of chopstick can be driven into afirm root ball farther away from the trunk to keep the wire to the outside.

Twist this wire together with the one at the nextcorner, and bend the tail of the next wire across the narrow part of theroot ball (Figure 25). There is no need for the wires to be tightened toomuch, since we will finish tightening them all together with the final wire.We are, in effect, creating a wire basket to distribute force evenly aroundthe nebari. The final tightening will cinch the entire basket at once.Repeat with the next wire.

When you get back to the place you started, you willrealize that you have no wire to twist with your final tail. Use a piece ofwire of proper length and loop it around the first wire you tied down,twisting it to provide you with the tail you need. You will then twist thetwo tails together, and this will be the spot you will tighten until thewires hold the nebari snugly (Figure 26).

Add Soil

The tree is now tightlywired to the pot. This technique produces an evenly distributed band ofsupport far enough from the nebari that the bark is not compromised and thetree is completely immobile. Since every tree is different, it is difficultto document every available technique for bridging gaps in the nebari, orworking with a difficult root system. However, this is the basic techniquethat will provide your tree with the security it needs to thrive with normalcare.

The time has come toincorporate new soil into the pot. Using a chopstick, carefully work thesoil between and under the roots, removing all air pockets as you go aroundthe entire tree. Plunging the chopstick into the soil vigorously andrepeatedly is a recipe for pulling feeder roots above the soil.. A gentlecircular twirling motion is gentler for the tender roots. Don’t be toovigorous when performing this technique. Try not to mix your regular soiland the drainage layer at this time. When no more soil will easily settleinto the roots, remove any excess. Have your helper hold the trunk securelyand thump the sides of the pot with the heel of your hand to settle any moresoil that might be useful.

This is where that whiskbroom from your bonsai kit will be very useful. It is designed for onepurpose: to finish fresh soil added to your pot (Figure 27). Holding itgently, drag it lightly away from the nebari toward the edges of the pot.Proceed all the way around your pot. Excess soil can be collected in yourhand at this time and saved for later.

Bonsai soil should not bemounded up at the tree, it should be flat and level across the pot. If youmust mound your soil, your tree is in too shallow a pot. Mounded soil washesaway with every watering, so be good to your tree and pot it correctly. Thelevel of the soil should be just below the rim of the pot (Figure 28). Thiswill ensure that water will remain in the pot to soak the root zone, and notrun over the rim as your soil compacts over time.

The final step with your newsoil is to tamp it with a small trowel. The imported trowels have a pointedtip for getting into corners. This is a cement mason’s margin trowel (Figure29) left over from a previous career. They are available at any buildingsupply store. The blade tends to be large for some bonsai, but they areeasily shaped on a bench grinder. For extremely large bonsai with very lowbranches, one with a much longer steel handle out to a wooden grip is veryhandy.

New Zealand sphagnum moss isa white sphagnum with a very consistent texture. It has none of the negativeproperties of green sphagnum moss. It is a very simple process to scrub iton your largest soil screen, reducing it to small fibers. A very lightsprinkling of sphagnum on top of your soil prior to watering (Figure 30)will help settle the soil and keep it in place, as well as retainingmoisture a little better. Water so that all the excess fibers are washed offthe pot. Be careful not to use too much!

Water Well

Watering is the last stage in repotting. Using thegentlest shower available, water until the runoff from under the pot isclear. Even freshly sifted bonsai soil retains a good deal of dust, and whenyou first start watering, this will be washed away. Do not immerse afreshly repotted tree to water it! Immersing the newly repotted treewill just lock the dust into the soil. Your tree is now repotted and readyto go to a protected spot on your bench.


The period after repotting is a tender one for yourtree. Keep it protected from excess sunlight and heat (although fortropicals, heat is a key to recovery), and especially from drying winds.There is no need to “balance the top with what you have removed from theroots.” This old wives’ tale will weaken and even kill your tree. The rootsyou have removed need to be regenerated, and it takes the foliage to dothat. Just keep your tree from drying out. After 2-4 weeks, you may beginfeeding your tree again, and put it in a less protected spot. You will seenew growth as soon as new roots become established.


These are some of the techniques and tools used in theprocess of repotting a bonsai tree. It is important to learn the principlesinvolved, since every tree is different. Once the principles areestablished, creativity is the key to supporting and protecting yourvaluable trees. Good luck and happy repotting!

[1]Perched Water Table. Wikipedia, the free encyclopedia. Available at Accessed 7/23/06.

[2]Perched Water Table. Accessed 7/23/06.

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