Posts tagged “Repotting

Japanese Maple Root Arrangement

Way back in 2011 I remember seeing this Bonsai Tonight post of a Boon Manikitivipart workshop where a participant tried out a root arranging technique of the deciduous bonsai genius Ebihara. What a great idea, right?

Last summer I acquired a maple that turned out to be perfect to try this technique on. It already had several years of root training therefore a good number of flexible lateral roots were present. Still, a fair amount of prep work was needed. The base of the rootball needed to be completely flat and all unnecessary roots removed. Hopefully this will improve the nebari as I rebuild the branch structure of this tree over the next several years.

As a side note, Boon posted an update about the tree in the Bonsai Tonight post on Facebook. Apparently using plywood was a mistake as it rotted quickly. Keeping that in mind, I used pine.

">IMG_20150324_201527 IMG_20150324_200736~3

Repotting New Black Pine

This pine was the subject of a recent post. The main goal for the next few years is to encourage backbudding so I can reduce the length of the branches. Grafting may even be in the agenda. To achieve these things, I will need to make sure the tree is vigorous and comfortable in its pot.

My understanding is that pines are best repotted just before the buds start to move. How can you identify this time? My friend gave me a handy tip: break off the tip of a dormant bud and check back the next day. If there is sap flow, the tree is coming out of dormancy and it is a good time to repot. Another indicator is if the roots have started to grow, indicated by white tips.

This tree tested positive for both of these indicators, therefore repotting was a go. For those of you in my climate – keep in mind this tree was just flown out from the Vancouver area in Janurary, and spent the winter in my garage at about 4 degrees C, therefore it is weeks ahead of any pines that were wintered outside.

Repotting my largest Thuja

Its not so much the tree that is huge, but rather the ‘coffin’ that it is planted in. When it is a bonsai, it will be an easy one-person tree… but its still my biggest Thuja (actually, I think its my biggest tree period).

I collected this in the fall of 2010 and did not want to disturb the huge flat root system, so I just built a box around it. It took two people to lift it, but the main issue is that I was stupid enough to build it out of plywood so it was starting to fall apart after a few months.

The purpose of this repotting was simply to put it in a more sturdy box that is about 1/3rd the size, and to wash some of the mucky soil away from the inner rootball.



Spring Work on a Siberian Elm & Bonsai Aesthetics Aluminum Wire

This tree took a step forward over the last couple of weeks, but still has a long way to go. It is one of several Ulmus pumila I got from this old hedge in 2010.

Just out of winter storage

As a side note, this winter I ended up with about 10 kg of Robert Stevens’ Bonsai Aesthetics aluminum wire. This is the first tree I actually tried it out on. It is pretty good stuff… only slightly softer than Japanese anodized aluminum with a bit less holding power, but at a fraction of the price. As is typical with aluminum on deciduous trees, I found myself using wire about 1/2 the thickness of the branch to achieve the desired bending power. It is worth noting that this wire is pure glossy black, as opposed to the copper-ish colour of Japanese aluminum wire. It will be interesting to see how the colour stands up to the elements over this growing season.

Setting some secondary and tertiary branches with Bonsai Aesthetics aluminum wire.

Root work came next. This is the first time that this tree has had focused root work since coming out of the hedge. Almost all of these elms had massive taproots. This one needed some work with the reciprocating saw and a die grinder to further reduce the taproot. Furthermore, a few excessively long roots had to be pruned back. This may look extreme, but every root I have cut back on one of these Siberians has produced new roots near the cuts – even tap roots 15 cm in diameter.

Reducing a massive taproot with a reciprocating saw, then a die grinder fitted with a carving bit.

The root system of this tree is not ideal, and needs much further reduction, but this is where I left the work for this year.

This Nick Lenz pot was the right size for the rootball, but the tree is not planted at the right angle. I'm not concerned about that right now, since this tree is still very much in training.

This Elm has an excellent trunk for a classic informal upright design, but the nebari is terrible due to the presence of large taproots. On an informal upright elm, the nebari is one of the most important features. Root grafting may be in this tree’s future.

Taxus cuspidata ‘nana’ Planting Angle Adjustment

The main purpose of this repot was not horticultural, but rather to adjust the planting angle of this Dwarf Japanese Yew. It has been tough to get this tree at the right angle due to the presence of thick sections of downward growing trunk which I have been rather timidly chipping away at (the tree was developed as a ground layer). You can read more about the history of this tree in my progressions page. This tree has been slow to develop, largely due to the long period of time spent replacing the root system. It is finally at the point now where I can solely focus on its development as a bonsai. It does admittedly have a few years to go before it is show ready.

The tree last spring. The tree looks unstable at this angle, and the direction of the first branch is upward. This branch will be pulled down eventually, but correcting the planting angle will reduce the degree to which the branch has to be lowered.

The tree before repotting, propped up at the intended angle.

After grinding away some of the offending 'root' (which is actually a section of trunk from where the ground layer was separated). Yew develop fantastically dense fibrous root systems. It is important to really open them up during repotting so soil can be worked in. The final bits of original nursery clay were also hosed away.

The result. I believe that this is the best angle for this tree. It also went into an aged yamaaki pot which may look a bit small right now, but I think will be ideal when the intended silhouette of the tree is achieved.
This tree will not be repotted again for several years.

Tired Old Potentilla fruticosa

The potentilla that is the subject of this post was collected about 10 years ago by a friend of mine. I have admired this tree for some time, as potentilla’s of this size and drama are quite rare. When I had the opportunity to buy it for a reasonable price last year, I didn’t hesitate!

Potentilla fruiticosa yamadori


However, this tree has some serious issues and serves to illustrate some limitations of potentilla for bonsai. In a recent post, I said that potentilla are one of my favourite species. They are certainly not perfect, however. Many people will refer to the limited longevity of potentilla. While they are hard to kill, their weedy growth habit is subject to dieback. Their biggest issue, however, is wood rot. This tree is a perfect example of the issues that arise with potentilla over time.

When designing potentilla bonsai as a deadwood species, you must be very conscious of the soft wood. It is nowhere nearly as robust as the deadwood of other deadwood species such as Thuja and Juniperus, and requires extra care. This means treating at least once a year with a penetrating wood hardener, and keeping the deadwood clean and dry. This is the product I like to use.

These techniques were not applied to this potentilla over the last decade, and as a result it has lost much of its structural integrity as a result of rot. Some of the fine jins near the base of the tree also crumbled away when I first laid hands on the tree last summer. The tree is literally falling apart. To make things worse, was planted in a very mucky organic soil mix which takes a long time to dry out.

The purpose of this spring work was mainly to take steps to minimize the advancement of the rot by doing the following:

  • Remove as much of the rotted wood as possible
  • Bareroot the tree and replace the soil with a coarse inorganic mix
  • Plant the tree more upright so that the deadwood is far away from the soil surface
  • Treat with limesulfur, then wood hardener

Crevices such as this are highly at risk of rot, especially if they are not kept clean and dry.

This organic soil mix holds far too much water. This rotted the jins that (used to) lay on the surface and also creates too much humidity for the deadwood that lies above the soil. It is worth noting, however, that the tree grows fine in this soil. Potentilla will grow well in almost anything!

The video clip below shows the extent to which the rot has compromised the structural integrity of the tree.


This is the new pot. It is a yamaaki pot with some signs of age. It is far from ideal, but I think it is a slight improvement on the current pot. I think this tree is ideally suited to a crescent stone, but I have not been able to find the right one yet!

After much struggling, I decided to break the pot. The unusual shape made it very hard to get the tree out and, given how fragile the tree has become, I did not want to pry on it too hard. This pot was made by the previous owner and he warned me that I might have to break it - sorry! :)

Barerooted with the hose and trimmed. You can see that the root system is strong despite the difficulties the tree has presented to the bonsai design.

The tree is so "floppy" that it had to be tied to itself in order to achieve the desired angle. This guy wire is hidden at the back of the tree and can be adjusted if needed.

Thats it for now. Much cleaning and wood preservation still needs to be done, but I think that the deadwood is much safer now than it was before.

The back of the tree is quite interesting as well. As the structure of this tree continues to deteriorate, I am sure that I will have to keep other design possibilities in mind.

Ginkgo is Early… Time to Repot

Today is March 12th, and my Ginkgo is already showing green buds. This means it is the ideal time to repot. This is more than one month earlier than I am accustomed to seeing movement on this tree.

The last time I repotted this tree was in 2010, and it was not until April 17th that the buds were starting to move! This seems to be the same throughout the bonsai community… a warm winter means early spring.

I am happy spring is here, but I am always concerned about taking my trees out of winter storage, then having to shuffle them around again when it becomes -15C in April 🙂

The ground is already thawed so I pulled out my ginkgo and brought it to a Toronto Bonsai Society meeting.

Normally I don't see this sort of action on this tree until mid-late April!

This is the new pot, which I got on a recent trip to Japan. It is probably 20-30 years old, based on the patina that is starting to develop. The shiny blue glaze has begun to relax into a complex, matte colour which I absolutely love.

The pot has no stamp on it. Nevertheless, it is a very high quality pot... heavy, but with thin walls. It will have no problem standing up to Canadian winters.

The tips of the shoots are just turning green, and the tips of the roots are just turning white. This tells me its a good time to repot.

All done! I think the new pot is a very nice fit. The old one was great too, and I was happy with it for 3 years. But I think its time for a change. This pot will really make the fall colours pop (unlike the last one) and is also suitable for the winter image. Can't wait for fall!


Repotting a Very Rootbound Satsuki Azalea ‘Kaho’

Repotting mature trees is different than repotting trees in development. Mature trees are usually repotted for maintenance purposes, so the root work is less dramatic and much less technical than the sort of work used for trees in development. At a recent workshop, I observed the repotting of an extremely root bound imported Rhododendrum indicum ‘Kaho’. This is a species that I have never worked with since I sadly don’t have the proper overwintering environment for azaleas. Still, its fun to watch and learn 🙂

The bonsai in question. The owner has had this tree for 3 years. He believes that it has not been repotted for 8 years, and had reached the point that water could no longer penetrate the root ball. As a result, the tree is weak.

The kanuma soil has almost completely broken down, and the pot was absolutely crammed with the fluffy roots that are characteristic of azaleas. The first step after removing the tree from the pot was to clean away the surface soil.

One of the most important tasks in the repotting was cleaning out the bottom of the rootball, all the way up to the base of the trunk. This area is most prone to rot, so cleaning it out well allows it to be inspected and refilled with fresh coarse grade kanuma. About half of the excavation is complete here.

A saw was used to trim only about 1.5cm of roots all around the perimeter. Since the tree is weak, a more aggressive root reduction may have been detrimental to the health of the tree.

All hanging superfluous roots were carefully trimmed back so that they were flush with the rootball. This picture shows the extent to which the bottom of the rootball was excavated.

The tree is going back to the same pot. There was a unanimous agreement that this pot is unsuitable for the tree, although the owner will be repotting the tree again next year once it regains strength. Hopefully he has found the right pot by then :)

With such a deep "pit" in the bottom of the rootball, simply making a mound of soil in the bottom of the pot is not good enough. Thee tree was held upside down and coarse soil was filled into the cavity. A chopstick was used to fill all of the voids. This is a step that is unique to trees with mature root systems - particularly azaleas.

To prevent losing the soil, the pot was also put on upside down. Getting the tree at the correct height in the pot can be tricky when this method is used, but this time it worked just fine the first try. Someone commented that this must be how they repot bonsai in Australia :)

The tree was securely tied into the pot, and the pot was submerged in water for several minutes, thus completing the repotting.