Bonsai Tool Care

Part 20 of a series by Eugene Howell

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bonsai toolsTools are critically important to bonsai. The art of bonsai itself has specialized tools made and used only for creating beautiful bonsai trees. However, during a local bonsai club meeting this year, the guest artist, who was giving a demonstration, made a comment on the apparent lack of care that had been shown to the tools our club had provided him for his demonstration.

While this was obviously an embarrassment to the club, the truth is that most of us do not give our bonsai tools the care they should be getting. This is especially unfortunate, not only because they’re expensive, but also because our trees can suffer from having poorly maintained tools used on them.

Something which never ceases to amaze me is the cost of bonsai tools. They are expensive. It’s not uncommon to pay $65 to $90 dollars for a pair of eight inch concave cutters and over $100 for the eleven inch pair. Bonsai scissors are just as bad. While you can find lesser expensive ones for around $40, you can easily find ones that cost over $100.

It would seem logical that when you pay that much for a bonsai tool you would do everything possible to keep it in excellent condition. Yet far too frequently, when I look at the tools people bring to club meetings, I notice that they’re covered with hardened sap, have dull cutting edges, and sometimes are beginning to rust.

Now, before you begin to think I’m too judgmental, let me point out that there have been occasions when I’ve looked at my own tools and found that I had forgotten to clean them after the last pruning, however, I do try hard to keep my tools in a clean and sharp condition.

Bonsai tool care

The first thing to do, after working on a tree, is to make sure you clean the cutting blades. If the job only took a couple of minutes then you can wipe the blade clean with a rough cloth. A word of caution is appropriate at this point, the cutting edges on some of these tools are extremely sharp so be very careful when cleaning them.

If your styling job has taken some time and a good bit of the sap is already hardened on the blades, you’ll need to use a rough cloth moistened with something like “Purple Power” or any other strong cleaner. This will do a good job removing the sap, but keep in mind that the blades will tarnish with use so don’t confuse the tarnish for hardened sap. After cleaning with this type of cleaner it’s very important to lubricate the tool well with WD-40.

No matter how much care you give your tools, the cutting edges will eventually become dull. This is especially true if you use them to cut roots. This is where you can damage your trees. By cutting branches with dull tools, you leave ragged edges on the cambium layer that in most cases will not heal-over properly. A few months later, instead of a nicely healed and nearly invisible prune spot, you’ll have ugly rotted wood showing.

Bonsai tools are made of hardened steel, so they hold their edges for quite a while. Nevertheless, they require periodic sharpening. The process of sharpening is not difficult, but it must be done correctly or you will wind up making the cutting edge worse.

The sharpening process itself is beyond the scope of this article, but I’ll insert a video at the bottom.

Depending on how much bonsai work you do during the average month, you may need to sharpen them every three or four months. Your tools will tell you when they’re too dull. For example, when you attempt to cut a twig, if the scissors cut only part way through and then begin to bend the twig, it’s probably because they’re dull. Or you may notice that when pruning a small branch there will be lots of small ‘strings’ of bark left at the edges of the cut, rather than a crisp, sharp edge. This too can be a sign your tool is getting dull.

There are sometimes other causes for these types of occurrences. Sometimes a tool can become bent or the pivot joint can become loose. To isolate the cause, close the cutting edges until there is only a very slim sliver of light showing between them. Examine the top, middle and bottom of this sliver of light to see if any small portion of it is suddenly wider than the rest. If so, the blade has been bent (likely as a result of trying to cut too thick a branch) and unfortunately there is nothing simple that you can do to correct it. Set the tool aside for use only in cutting roots and then order a replacement tool.

If that sliver of light is even all the way down the blade, then hold each handle in a separate hand and gently wiggle them back and forth to see if the joint has loosened.
The fix for this problem is to tighten the rivet that holds the scissors together. You can do this by placing one head of the rivet on a steel surface and gently tapping the other head with a hammer. After each tap check the blades to insure you have not over tightened the rivet. If, despite your effort to avoid it, you do happen to tighten them too much and the blades begin to rub hard against each other you can correct this by stacking up two or three large washers on the steel surface, place one head of the rivet in the center of the top washer’s hole and using a punch or nail, gently tap the other head. This will cause the rivet to loosen. Do all this gently or you can spend all day going from too tight to too loose.

Although you won’t use them very often, it’s worth having least one pair of 11 inch concave or knob cutters in your tool kit. Periodically you’ll face a task of cutting a branch that is simply too large for the 8 inch cutter. Using the 8 inch cutter will probably bend the blades. But, by having your 11 inch cutters you can avoid having to use a saw which can damage the bonsai.

Finally, don’t ever put your tools away without having first sprayed them with WD-40 or an equivalent protective oil. Sap can cause them to rust quickly, as will your finger prints. It only takes a few seconds to spray your tools. Remember that your tools depend on you to keep them in proper shape…..always do so.

Photo credit: Gary Howell

Part 19 of this series : Part 21 of this series