Repotting 101: The tools of repotting

Overview

This post is not meant to be about repotting in general as I have already written several posts which deal with the subject (simply click the tag "repotting" to see all related posts). Instead I would like to focus on the tools which are useful when repotting as I am convinced that there are some who are not familiar with the tools and how they can make repotting that much easier and quicker.

The Sickle

I must admit that it was not too long ago that I myself actually only started to use this tool as the local teachers from whom I drew knowledge did not use them, from what I saw. However now that I have begun using one, I am not quite sure how I managed without it.

There are several sorts of sickles available; some have a curved blade, some are shaped 90 degrees to the shaft, some have teeth and some don't however they all have a common function.

Function

I have heard it said that bonsai pots with an internal lip, or an "undercut" are inferior in some way or that they are not "real" bonsai pots. This is utter nonsense. The inner form of the pot follows the outside shape of course and I would assume that for the pot maker it acts as a strengthening rib helping to prevent the lip from sagging. However such a detail presents a challenge when it comes to repotting as roots will fill this area making it impossible to lift the tree from the container easily. This is where the sickle is indispensable as it allows you to cut through these roots, severing them and making it possible to lift the root-ball from the container.

Image caption. A sickle is used to create a narrow gap between the root ball and the container wall. This makes lifting the tree out the container possible.

In other instances where you have a straight sided container or even one with a draft angle, but where the tree has been growing for some years, the root-ball can be very difficult to lift. Once again a sickle is invaluable as you can use it to make a narrow groove between the side of the container and the root-ball. This gap is all that one needs to make lifting the tree possible without needing to break the container.

Image caption. It would take a long time to rake this bottom mat of roots out, so a sickle can be used to quickly saw the bottom layer off.

The last use for the sickle that I can immediately think of is to quickly remove the mat of roots from the bottom of the root ball. After some years in a bonsai container, more and more roots will develop at the bottom of the root-ball forming a densely woven mat. When you see a tree which is overdue for repotting, it will usually look like it is pushing itself out of the container; this is caused by a particularly thick mat of roots. I have seen some growers removing this with a reciprocating electrical saw. Personally I find this to be a little harsh. I prefer using a sharp sickle, or one with serrated teeth as I feel it is less invasive and more controllable, plus you can easily do it without an assistant.

Rakes and Hooks

There are many shapes of root hooks and rakes. Some have one tooth, some two and some three. Some have metal handles, others have wood and some are combination tools where a pair of tweezers or a spatula can be found on the opposite end. 

I use a variety of these tools when I am repotting, depending largely on what the particular tree requires. I like using the 2 pronged rake with a very open angle between the teeth for the bulk of the work and to rapidly remove old soil from the sides and bottom of the root ball. Of course this is too big for smaller trees though so one of the smaller, combination rakes are better suited. I also use these smaller rakes for more detailed work on the root-ball, or for the top of the root-ball.

Function

Essentially these tools are all designed for two purposes; to remove old medium and to organize the roots. 

Old soil refers to the growing medium in which the tree has grown since it was last repotted. This medium might have broken down into particles which are now too small to allow good drainage and oxygen exchange. It may also have compacted over time with repeated watering. This should now be removed and replaced with new medium which will help to invigorate the tree.

The most commonly seen tool used for repotting is the single toothed one imported from China with a red plasticized handle. Although this tool can work its not particularly effective in compacted media as it simply makes a groove. Much more time is required to successfully remove the old growing medium. On the opposite extreme, the more teeth in the rake the more likely you are to damage roots when raking them out, hence why I suggest that you use a rake with fewer teeth where you are likely to encounter large roots and a rake with more teeth where finer roots are found.

Image caption. The finer and more numerous teeth of the 3 pronged rake is ideal for raking out finer roots.

Root Cutters

As the name suggests, root cutters are tools which have been designed to cut roots. The metal teeth have been designed to be more robust than say for instance branch cutters. This is as they are used in an environment where stone or other hard particles might be encountered and of course roots of various thicknesses. 

Image caption. A Root Cutter in action on the old roots of a Japanese black pine.

There are a few different sizes of root cutters. The appropriate cutter should be used, using too small a cutter on a root may result in the teeth being bent and the cut to the root not being clean. 

Function

I believe it's pretty obvious to us all what these tools are for as its all in the name, however if you are in doubt they are used for shortening thick roots. Thick roots are those which cannot easily be cut with scissors. Unlike branch cutters where the cutting blades are angled to the side, the cutting action is at the front of the tool. 

Image caption. The very largest root cutter I stock was extremely useful for reducing the stub of the old trunk on this Hackberry ground layering. A saw was used to cut the layering off but the cutter was then used to carefully reduce the stub as a saw would most likely have damaged many of the young roots.

Its important to reduce the length of these thick roots when you repot. Thick roots essentially become storage spaces for a bonsai tree. The type of roots we wish to encourage are finer feeder roots as they are responsible for absorbing nutrients and moisture from the soil and so can support highly ramified trees. You can to some extent see pruning these roots almost the same as pruning sacrifice branches in the canopy ie they produce "back-rooting" and increase ramification of your root system, which is very important.

Image caption. The root above was cut at an angle using a root cutter. New roots then emerged from the bottom.

The angle of the cut made when removing these roots will determine how the future roots will grow. If its in the ground its not critical but if near the surface, where you can see them then it matters more. No matter where the cut though, it is always important that the cut be as clean as possible to reduce the time needed for healing.

It is always important to consider what container you ultimately wish to get the tree into. Should you not cut the thicker roots harsh enough in the early stages of development and then find after some years you need to cut way back, you will inevitably eliminate much of the finer roots which developed also.

Due to the robust design of root cutters I actually find them to be some of the most used tools in my toolbox, and I use them extensively for quickly removing branches after which I reduce the cut further with an appropriate branch or knob cutter.

Scissors

As you are aware, bonsai scissors are not merely scissors. There are many subtle and not so subtle differences to a pair of bonsai scissors when compared to kitchen, paper or even standard garden scissors. 

The scissors I would recommend most for root work will be the design of scissors usually referred to as the General Scissors. These have large handles which can accommodate several fingers for extra power and they have fairly long and thick cutting blades which enable them to cut fairly thick growth.

Image caption. Don't use the same scissors on your tree's roots as you do for the branches.

One point which I would really like to stress is that whatever scissors you use for your root work, don't use the same pair for work in the canopy. Scissors used for root work are quickly damaged by stones which you will inevitably and inadvertently cut into. They are also blunted rather quickly, for the same reason. 

Function

When growth is thin enough you can use scissors to shorten it. I would generally work in this order; first to cut the thicker roots with a root cutter and then shorten the thinner roots with a pair of scissors.

Image caption. After trimming with a pair of sharp scissors the rootball of this Chinese maple is flat at the bottom and neatly trimmed all round.

It is important that once you are done with trimming the roots the tree should be able to stand upright at the correct planting angle without being supported. In the beginning when your tree is young then it may need to be assisted but after a few years this will become more relevant. The reason for this statement is that you want more or less even development of the roots all around the root-ball. If you are forced to place the tree too far back in the container this leaves little space for roots in that area to develop and this might lead to weaker growth above it also.

Soil Sieve

In fact I should actually have dealt with this tool or accessory before we even started on the tree as it is best that you have your growing media ready for use before you expose the roots to drying. You want to minimize this exposure as much as possible as at this time the roots, especially the fine ones, are at risk of drying out and dying.

I don't honestly know how you can repot a tree without having access to a set of sieves, as it enables you to get rid of fines for instance if using stone or bark in your mix.

Image caption. We stock a very handy 300mm diameter soil sieve set made from Stainless Steel with three interchangeable mesh sizes.

From what I have seen, you get soil sieves with a wooden frame and a metal mesh and then you get all metal versions. Some of them, such as the one I stock, have interchangeable mesh screens and others are fixed.

Function

The typical particle separation we wish to look for in our growing media is 3, 5 and 7mm. Finer particles do have a purpose though, for instance as a surface dressing, but in the growing media itself we need to be careful of too fine particles as they reduce oxygen penetration, retard drainage and increase water retention.

Image caption. Sifted growing media, organized into various particle sizes ready to be mixed.

The soil sieve enables you to take a bucket full of growing media and separate it into different grades. Particles larger than 7mm can be used for the drainage layer, smaller than 7mm but larger than 5mm can be used in the lower third portion of your container. Smaller than 5mm but larger than 3mm can be used in the second third, and everything smaller than 3mm at the top. 

Why is this important? I must say that when I first began learning about bonsai nobody I knew sifted their growing media and essentially the media was just dumped into the pot around the roots. However, what I have come to realize is that it does matter as media at the bottom of the container will dry at a far slower rate than media at the top if all the particles are roughly uniform in size. This is not desirable as essentially you will never be able to achieve a state where the media near the bottom of the pot is beginning to dry out, because in order for that to happen the top will probably have to be bone dry. This would mean killing all your surface roots. By using large particles at the bottom the spaces between the media is far greater allowing for more air movement, reduced water retention and increased drainage. At the top level which is likely to dry out far quicker we compensate by using finer particles.

Soil Scoops

The benefit of using a purpose designed and made bonsai set of scoops is that they come in 3 different sizes. Each of the different sizes will nest into its bigger brother, which makes storage or packing a little neater too. You will also find one size more comfortable to work with than another on a particular size of tree. The sharp angle of the scoop helps when you need to get media into a pot around a tree with a large and low canopy.

Image caption. Both stainless steel and plastic scoops will not rust, which is a good thing as soil scoops are often forgotten outside, get wet and are really just abused all round!

Scoops are typically available in plastic and stainless steel. Which you prefer is largely personal preference. I have both plastic and metal sets which I use and have used for many years now. Both have worked well for me and are still in very good condition.

Function

The primary function of the soil scoop is simply to get your prepared growing media from whatever vessel you are storing it in, into the bonsai pot, and to do this without any mess. The scoop makes it possible to deliver media to precisely where you want it also to fill a gap or get it between roots or some other orifice which is hard to reach.

Sprayer

Its very handy to have a sprayer bottle close by with water when repotting. This can really be anything which will deliver a mist spray of water. You can even use an old detergent sprayer bottle and mechanism, just make sure that it is thoroughly cleaned so there are no remaining chemical residues.

Image caption. A fairly new product I began importing is the sprayer attachment seen here as part of our Plant Protection Collection. The attachment can be screwed onto any plastic drinks bottle and used to apply pesticides or water, in the context of repotting.

Function

When roots are exposed to the sun or wind they will dry. Once roots dry out you can consider them dead. So you need to take steps to avoid this from happening when you repot. This is why I would suggest you repot in the cooler parts of the day, perform it in shade and preferably on a day with little wind. Having a spray bottle at hand you can at any time just give the roots a bit of a misting to keep them wet.

Ice Pick

Now I do not blame you if you have no clue of what I am talking about at this stage! Essentially it is a tool traditionally used to break large pieces of ice into smaller pieces. So what role does it play in bonsai?

Function

Have you ever observed how some bonsai appear to be climbing out the container? Sometimes this is due to repotting, but then the entire tree is pushing out the container. In this instance I am referring to where the tree trunk and nebari become increasingly more exposed. This can be due to a few mistakes made in repotting but the most likely cause is that when the tree was repotted the root-ball immediately adjacent to the trunk was not properly aerated. Eventually this zone becomes so compacted that no new or young roots can be found. So when the owner repotted they could not cut back as far as they would have liked. Over successive years the problem gets bigger and bigger.

Image caption. A shaped, blunt old screwdriver makes a good ice pick and enables you to aerate the root-ball. 

The ice pick enables you to gently make holes into the root-ball in this area to allow water to penetrate and for oxygen exchange. I don't currently sell a tool like this but I made mine from an old screwdriver, the point of which I shaped to a very rounded point. You do not want to spike live roots, the action of pushing the pick into the soil should be slow and deliberate, working from the outside perimeter of the root-ball to the inside. The root-ball should feel sort of spongy when you are done. This is an especially good technique for conifers as they do not like to be bare rooted.

Drainage Mesh

All bonsai containers have at least one large hole in the base. The purpose of this hole is to quickly allow water to escape when you water your trees, as it is never a good idea to keep roots immersed for too long.

Function

If you do not place something over the drainage hole, your growing medium will simply fall out the bottom. What you choose to place over the hole is quite important as you do not want something too fine which can quickly get blocked up, but on the other hand you don't want it so coarse as to allow your media through.

Image caption. Wire keeping the drainage mesh in place.

Cut a piece of mesh so that it is a bit larger than the hole. Then by means of a piece of aluminium wire secure it into place so that it cannot move when you are filling the container with more media, or when you put the tree in and need to move it around a little to make some adjustments. 

Wire Tie Down

I am not actually too sure what to call the wire and loop you make to wire your trees into the pots they're growing in, but wire tie down seems to make sense.

Living in the Cape, where we are subjected to winds, it is very important to wire your newly repotted trees into their containers. If you live in an area which also receives wind then I would strongly advise you to heed this piece of advice also.

Generally the same aluminium wire which you use to style your trees can be used to tie the tree down. Sometimes copper wire is used but this is really only in the case of very heavy trees.

Function

Just in case you did not know, those small holes in the bottom of your bonsai pot are for these wire tie downs. If your container does not have them then you can use the drainage holes instead. If your pot only has one hole then you can use a thick piece of wire, stick or other similar item which is longer than the hole, to coil some wire around, then push the wire through the drainage mesh covering the hole. The stick or whatever you have used then anchors under the pot.

Image caption. Aluminium wire tie downs prepared and bent out of the way, until a tree is placed into the container.

For the moment, you should simply cut lengths of wire which will be sufficiently long to anchor the tree into the container and push them through the holes so they are ready for when you want to place the tree into the container.

Just to be sure, you will cut a piece of wire, push it through the one hole. The other end you will push through the other hole. Once you have placed the tree into the container you will bring these two wire ends together and twist them until the wire is holding the tree tightly down. 

Chopsticks

No need to explain here, just standard wooden chopsticks. If you don't have some then a dowel rod with do, or pretty much anything which is around pencil thickness or thinner and which has a slightly tapered tip but not sharp.

Function

In the past I was shown how that after repotting you submerge the entire tree into a basin of water and when the air bubbles have stopped coming to the surface you can lift it out again. The purpose was to ensure that there were no air pockets in the container.

Image caption. Make sure to work out all air pockets before you water your tree.

This is fine I guess if you are using soil and stone etc but some modern media is lighter than water and will float. Aside from this its not always possible to immerse your larger trees into a tub of water, plus it becomes extremely heavy to move when weighted down by water. So it is important that you ensure there are no air pockets by other means. This is what you use the chopsticks for. After using your soil scoops to put your growing media into the container, using small circular swirling motions you make a small gap in the media in the pot using the chopsticks. The gap is then replaced by media which falls into the holes you make aided by gravity. You need to spend time on this and not be in a rush to do it properly. Roots don't grow particularly well in large pockets air.

In fact chopsticks have many uses other than the one I just described. For instance if you need to drastically alter the planting angle of the tree but don't have a good enough anchor you can knock chopsticks into the sides of the root-ball and anchor wire onto them. They are also useful for creating a lattice which you can secure into the base of the container when you are planting a forest. The individual trees can then be fastened onto the lattice.

Pliers

I know a lot of people think this is an unnecessary tool and that they can use the DIY version which is cheaper. I disagree having used both.

Function

The bonsai pliers actually has a lot of uses; I use it extensively to help me bend thicker, wired branches by grasping the wire and bending the wire in the direction I want the branch to grow rather than holding the branch itself as this gives me more control and allows me to make very tight bends. They are also very useful when working on deadwood as you can easily grasp wood fibers and twist or pull them creating a very natural look.

Image caption. Make sure to secure your tree well into the container. 

In the context of repotting however I use them to twist the wire tie downs until I have secured the tree into the container to ensure there is no movement. An important tip I would like to share with you on the twisting is that if you simply twist and twist the wire is going to snap - especially so if you are using aluminium. Instead, use a pull and twist action. In other words pull the twisted wire and then take up the slack by twisting. Pull action and then twist action. Be careful not to make the wire too tight and if necessary, and if you are anchoring over a surface root, you might want to place something over the root first to protect it from the wire biting in.

Spatula

I was always told not to press down on your growing media after repotting as this would compact it. When I think about it now the advice was not truly sound because if the media is that fine that it would be able to compact simply by me pressing down on it, then it would do so with simply watering it in no time either. 

With media such as graded stone, leca, pumice and akadama it is necessary to tamp them down a little and as they are graded they will not compact. What you use to tamp down can be your hands, a piece of wood, or if you have one; the flat spatula on the other end of a rake or tweezers.

Function

Quite simply the spatula will just help you to press your new growing media down to help it settle. It also creates a level surface. I admit that I largely use my hands for the bigger containers but the spatula comes in very handy for complex areas around roots or when working on smaller trees.

I also find the spatula useful when gathering moss and applying moss.

Watering Can or Watering Wand

Once you have completed filling your container with new growing media and have tamped it down you will need to water the tree thoroughly. It is always advisable to work with practically dry growing media as in this state it will fill gaps easier as it flows better. Wet media sticks to itself and carries a much higher risk of breaking roots, especially the thinner more delicate ones.

There are many watering cans and wandsor sprayers on the market today. I always found the watering cans commonly found in garden centers to leak, be cumbersome and unable to reach the container when a trees canopy extends past it. The spray is also very coarse and erodes much of your growing media. Likewise with the quick fitting sprayers which attach to hosepipes. Although there are one or two that I have used with a fairly fine spray, you really need something as fine as possible.

Image caption. When you water use a fine spray and water thoroughly till water pours through the drainage holes.

Function

After repotting you will want to water thoroughly. This is in part because the media is dry and you want to make sure that you wet all of it in the container very well, and also as you want to get rid of any fine dusts and other particles. Although using high quality media will have less of this waste in the bag, there is always some dust which forms during handling of the product. You don't want this to accumulate at the bottom of your pot and compact there, so you need to water until the water running from the drainage holes is clear.

Conclusion

So that's it. I think I have given a pretty thorough overview of the tools which I use and would recommend you consider using for the repotting of your trees.