Bonsai blog

Welcome back. With spring fast approaching it’s time to start on the first major job of the bonsai year; repotting. It’s going to be a rather image heavy blog so I’ll start with a why, when and how:

Why:

Bonsai trees do not require the large, woody, anchoring roots that trees in the wild need to prevent them from being blown over. It is necessary to develop a mass of fine ‘feeder roots’ close to the bottom of the trunk which will help the bonsai to take up water and nutrients more efficiently.

• Repotting provides the tree with fresh soil, including fresh minerals and nutrients which may have been leached out by the watering process or successfully used by the plant
• Repotting removes inefficient woody roots that have become too long and are taking up essential space in the pot
• Repotting improves the air circulation around the roots by removing unnecessary roots and old compacted soil
• When repotting we can work on and improve visible surface rootage

When:

Repotting should be carried out every three to five years, dependant on the age and vigour of the individual tree; younger trees can be repotted more often. NEVER carry out unnecessary repotting of trees, as it is stressful to the plant, and could kill it.

You should consider repotting a tree when its vigour starts to drop off i.e. if the tree sets less buds in the autumn, or if twigs or branches start to die off unexpectedly. Other signs that repotting is required are difficulty in watering a tree; water fails to penetrate the root ball due to the air spaces between the soil particles filling up with old root material and broken down soil grains. Root pruning can be carried out in the late autumn before a tree enters dormancy (usually for conifers and other evergreens), but is best carried out in early spring, just as it is beginning to break dormancy.

How:

Try to dry out the soil in the pot slightly before repotting. It is not important to add 'crocks' or other drainage material in the bottom of the pot – this simply uses up valuable space – there is little enough soil in the pot to start with! Prepare an ample supply of soil or compost before you start; this will minimise the stress to the tree (and yourself) should you have to stop halfway through the repotting process to prepare more. Soil should be sieved to remove dust, and it is often a good idea to prepare different grades (grain sizes) to use in different areas of the pot; larger grains towards the bottom of the pot, smaller towards the surface. If you are looking to change pots, or it is the first time you have repotted your particular tree, it may be an idea to prepare an extra pot (or two, if available) just in case the root ball does not fit in your new pot.

Refrain from fertilizing for up to a month after repotting. Appyling fertilizer can 'burn' weak new roots.

So that’s it for the whys, whens, hows, dos and don’ts. Below is a step-by-step guide to how you should go about repotting a bonsai tree. Kind thanks go to Mr Nobuyuki Kajiwara (Nobu) for granting permission to use the images I took of him repotting one of the Kew bonsai, a trident maple (Acer buergerianum) several years ago.

Carrying out the initial spring pruning. Pruning away any excess branches and buds at this point will reduce the 'workload' on the pruned roots when the tree comes out of dormancy.

 Many bonsai pots feature an in-turned lip which can make it almost impossible to easily remove the tree for repotting. A 'root sickle' is used to cut the roots and soil around the edge of the pot to release the tree easily (for more on tools and their use, see my previous blog Tools of the Trade).

After using the root sickle, the base of the pot is thumped to loosen up any roots that may still be gripping the sides of the pot.

The tree and root ball can now safely be removed from the pot.

A 'scribe' type tool is now used to tidy up the surface of the soil (a chopstick will do). This reveals any large roots that may require remedial work. The surface of the soil can be brushed down with a hemp brush to remove any old moss and debris.

The roots around the edge of the rootball are combed or raked out using a root hook (for more on tools and their use, see my previous blog Tools of the Trade).


Once the roots around the edge have been loosened up, the same process is applied to the base of the rootball.

Now, the excess roots can be removed. Roots should be cut at a 90 degree angle, leaving as small a cut surface as possible. Where possible, the cut surface of the root should point downwards.

Remedial work is now carried out on thicker, woody roots. A branch-splitter is being used to sever the roots.

The root pruning process is now carried out around the edge of the rootball.

The tree now undergoes a “test-fitting” in the pot to see how much more of the root ball still needs to be removed.

At this point, any changes to the trees position in the pot need to be carefully considered; a little to the left, further towards the front or back, or rotation to better show the front of the tree? Stand back and consider the planting position carefully, as you’ll have to look at it for the next few years..!

More roots are combed out from one edge of the root ball with the root hook and trimmed off to better fit the tree in the pot.
 

A thin layer of akadama soil is poured into the bonsai pot

A thin layer, less than a centimetre, of dust-free (sieved) akadama compost is now added to the bottom of the pot (I will write a future blog about various different bonsai composts and their uses). A small mound of compost is built up in the centre of the pot to fill the concave area under the root ball that has resulted from the pruning off of the large roots.

Retaining wires have been added through the drainage holes to securely wire the root ball in place (short wires to the back of the pot, longer ones to the front)

More akadama compost is now added round the edges of the bonsai’s root ball and carefully worked in with a chopstick to prevent any air spaces.
 

The periphery of the bonsai pot has been filled with soil, and more has been added to thinly cover the rootball’s surface. The retaining wires now hold the bonsai in place.

The tree is thoroughly watered

The tree is now thoroughly watered in. Water should be applied until it runs clear through the drainage holes, washing away any akadama dust that sieving failed to remove.

The surface of the soil has been coated with chopped, sieved, sphagnum moss; this helps to draw the moisture within the pot up to the surface, the area which is most likely to dry out quickest. Roots are more likely to be active in this top layer of soil, where there is a ready supply of water, air and warmth.  The top-dressing of sphagnum moss will also help natural-looking green mosses to colonise.
 

A small trowel is used to gently press the wetted moss into the surface of the soil.

Well, that's all from me (and Nobu) for now. I hope it proves helpful during your repotting endeavours!

- Richard -

Gwendolyn Anley – A British Bonsai Pioneer

This time around, something a little different; some bonsai family history. I would like to cast some light on a relatively unknown pioneer of British bonsai, Gwendolyn Anley.

Back in 1995, I happened to hear about a pair of Chinese junipers that had been lodged at a bonsai nursery for “intensive care”. Rumours of their unusual history piqued my interest, and I was soon able to make contact with their owner. The owner of the trees, who is now sadly deceased, was generous enough to donate these two Chinese junipers, and later a similarly historic Zelkova serrata, to the bonsai collection at Kew.
 

One of two Chinese junipers (Juniperus chinensis) donated to Kew Gardens in 2005.
It is grown in the distinctive “root-over-rock” style. (Accession number 2005-2013)

History of the trees

When the trees were collected we were fortunate enough to also receive detailed information about their history, indicating that they are possibly the earliest Bonsai imported into Britain that still survive in their pots.
 

We were lucky to be able to borrow and copy this image of the same bonsai
(Accession number 2005-2013) taken in 1956. Though the tree has aged,
and the pot has been changed, note the familiar, unchanging rock!

The trees were originally imported into Britain by Gwendolyn Anley, who was the great aunt of the donor. Mrs Anley was famous for her Iris and alpine plant growing, on which subject she wrote two books “Irises - Their Culture and Selection” (1946) and “Alpine House Culture for Amateurs” (1938).
 

Gwendolyn Anley at her home, “St Georges”, in Woking, with some of her bonsai

The donor was also able to loan Kew some of Mrs Anley’s photographs, which were taken during her travels in Japan where she studied the art of Bonsai in 1935. Other images were taken for inclusion in “Gardening Illustrated” magazine in 1946. Included amongst these photographs were images of the two recently donated junipers.

Writing on bonsai growing

I was interested to find that Mrs Anley also wrote one of the earliest English language articles about bonsai growing. A search of the Kew libraries revealed a book named “Miniature Gardens” published in 1955, and containing a final chapter by Mrs Anley entitled “Bonsai: An Introduction to the Japanese Art of Dwarfing”.

In this brief chapter she clearly explains the rudiments of bonsai care in which she is assumed to have had some degree of training. She probably aquired her skills while in Japan with her husband, Brigadier General Barnett L. Anley, who appears to have been there for ambassadorial duties. She writes:

“From my window I used to watch a Japanese [man] tending his trees. Every specimen in a large collection was examined daily, and during the summer the trees were watered three and four times a day, according to the amount and quality of the sun, the wind or the temperature. How many people in this country are prepared, or can afford, to give such punctual and unremitting care?”

Count and Countess Matsudaira with some of their huge collection of
miniature bonsai. This photograph would have been taken in the 1930s.

Time in Japan

Photographic evidence suggests that, while in Japan, Gwendolyn met Count and Countess Matsudaira, who were the best known growers and collectors of miniature bonsai (“shohin”) at this time. Count Matsudaira’s collection eventually reached a thousand specimens of excellent quality which he and his wife, Countess Akiko, tended with great enthusiasm. Whenever he was on a trip, he used to carry some of his favourite bonsai with him in a basket specially designed and made for the purpose! In 1934, about the time Gwendolyn was visiting Japan, Count Matsudaira was named the first president of the newly-formed Kokufu Bonsai Association. The Association is still extant today, running the most famous of the Japanese annual bonsai exhibitions.

Gwendolyn Anley maintained a garden named St Georges, in Woking, about which I found a wealth of information in Graham Stuart Thomas’s book “Recollections of Great Gardeners”. The donor of the bonsai trees indicated that her late aunt could be rather fierce, and this is borne out in Mr Thomas’s book when he mentions approaching the Anley’s gate to find a sign reading “Considerate people will shut this gate; others are requested to do so”. He also mentions another notice over the fireplace in the study reading “if you have nothing to do, please don’t do it here”!

He confirms Gwendolyn’s presence in Japan in the late 1930s, and notes that she “came back with a treasury of Japanese thoughts which altered her outlook in many ways”. Her bonsai are mentioned in passing: “I think it was the discipline and economy of cultivating these characterful pieces that proved the great attraction”. He finishes his article in a more forgiving mode, saying “she enriched my life with much kindness, refuting to the full whatever impression might have been gained by the two notices in early days!”

Following Mrs Anley’s death, her collection of bonsai were distributed amongst her relatives, whereupon most of the trees are assumed to have died. Four of her bonsai are known to have survived until recent times, and three of these trees are now in the collection at Kew Gardens.

- Richard -

As you can see from this selection of photos, autumn colour is starting to appear in the Bonsai House - and it's going to get even more colourful!
 

Front: Acer palmatum, now nearly 100 years old; Centre: Gingko biloba, about 30 years old; Back (not showing autumn colour!): Juniperus chinensis, approx. 80 years old.

 

The Ginkgo biloba bonsai tree has not been in the collection at Kew for very long. I only noticed this year that the yellow autumn colouring starts in the middle of the leaves and spreads out towards the stems and leaf-tips.

 

Gingko biloba leaves starting to show autumn colour.
 

The Acer buergerianum is starting to show autumn colour. With luck the leaves will soon be a stunning fiery red that it has displayed in previous years (image, below right)

 

Acer buergerianum as it looks now (left) and how it looked at its peak last year (right)

Zelkovas seem to vary greatly in their autumn colour, with most of the seedlings I have grown displaying yellows and oranges. I wonder if perhaps this tree was specially selected many years ago by a Japanese nurseryman for its distinctive red colouring?

 

Beautiful red foliage of a Zelkova serrata.

Behind-the-scenes

Behind-the-scenes, many of our Acer palmatum show a variety of seasonal colour. Most of these trees were grown from seed collected in Japan over 40 years ago, and show the variations in leaf colour that occurs when trees are grown from seed.

 

- Richard -
 

The Tools of the Trade

As promised, in this blog I’ll introduce the tools I use in the creation and maintenance of the Kew bonsai collection. As with many specialist hobbies, a grower might end up with a wide and varied collection of tools, not all of which are strictly essential!

It pays to purchase good quality tools a few at a time; a high quality tool can last a lifetime. There are many cheaper tools currently available which can quickly blunt, break, or are badly designed and uncomfortable to use. In several places I have suggested where a cheaper substitution can be made, rather than purchasing purpose built Japanese tools.

I’ve divided the tools into three main groups: repotting, pruning and wiring. Some of the tools “crossover” and are used for different purposes at different times of the year.

Repotting Tools:

Bonsai repotting tools, from left to right: a coir brush, a root hook, a repotting sickle, a miniature trowel, root pruning shears, two chopsticks (steel and wood) and a large pair of rootpruners.

This first group of tools are those which get used earliest in the year, for repotting, from late February through to April.

• Coir brush (left) - a coconut coir brush, usually used for cleaning off the soil surface before a tree is repotted. Far from essential(!), it can be useful for exposing surface roots for examination before they are pruned.
• Root hook (second from left) - the root hook is used for combing out the edges of a rootball before the roots are trimmed. It’s basically a strong metal hook with a comfortable handle; for quite a few years I used an old screwdriver that had been sharpened to a point and bent 90 degrees in a vice! 
• Repotting sickle (third from left) - the repotting sickle is used to cut a bonsai’s rootball loose from its pot so that the roots can be pruned. Some pots have incurving sides, which can hold a bonsai tree in a pot like a cork in a bottle! A strong, short-bladed knife can make a good substitute for a repotting sickle - mind those fingers!
• Scissors (top, third right) - it’s a good policy to set aside a strong set of scissors (or shears) for rootpruning. Not many of the soil mixes that I use contain grit, but some of the trees I look after have been potted into gritty mixes in the past; this can play havoc with nicely sharpened scissors. It’s a good idea to look for repotting scissors at a DIY store; I prefer these to the traditional Japanese rootpruning scissors.
• Mini Trowel (middle) - again, not the most essential of tools (I survived for many years without one of these) but now I have one I have found it surprisingly handy. Used for smoothing over and tamping down the soil surface of a freshly repotted tree before and after a sphagnum moss mulch is applied.
• Chopstick(s) (second right) - a chopstick is most frequently used for working fresh soil back in around the roots of a tree as it is repotted. It also sometimes gets used to comb out roots; it is a less brutal alternative to the root hook.
• Rootpruners (right) -yes, I’ll admit these do look like something the Spanish Inquisition would use to get you talking. Used for removing large roots where necessary.
• Soil scoop (not shown) - soil scoops are very handy for directing soil into difficult corners of a pot, but are not the most essential tool in the world of bonsai. A cheap and serviceable soil scoop can be simply fashioned out of a small, cut-down fizzy drink bottle!

 This is a Japanese sieve with three interchangeable screens. Using these I can produce the different grades (grain sizes) of soil I need to repot different species and sizes of bonsai.
 

Pruning Tools:

Bonsai pruning tools, from left to right: A small folding pruning saw, branch pruners, spherical knob cutters, fine branch pruners, fine pruning scissors, tweezers and leaf shears.

• Folding pruning saw (left) - a small pruning saw for removing branches and large roots. Not used very often, but it is indispensible for removing thick roots and the occasional branch.
• Branch pruners (second left) - these are used for pruning off branches, and make a flat cut. I’d expect these to be able to remove branches up to 15mm thick. A good set of branch cutters are one of the most indispensible of all bonsai tools.
• Spherical knob cutters (third left) - for removing branches, and occasionally roots. These are designed to make a concave cut, or take a “bite” out of a tree. As the cut heals over the bark rolls into the concave recess and the resulting scar is less visible.
• Fine branch pruners (middle) - a daintier version of the standard branch pruners, I’d expect these to be able to cope with branches up to about the thickness of a pencil. Mostly used for thinning out twiggy growth, these are quite slender and thus easier to insert into bushy canopy areas.
• Fine pruning scissors (third right) - another one of the more indispensible tools, these long-handled scissors can be used for cutting small twigs, leaf stems, needles and buds.
• Tweezers (second right) - another indispensible tool, and one of the most commonly used. Ideal for removing dead foliage or needles, weeding, fine wiring or just poking bugs. Never more than arms reach away...
• Leaf pruning shears (right) - occasionally it is necessary to defoliate, or partially defoliate, a bonsai tree (I’ll add a note to my “blogs to do” list to mention more about this later). These little spring-loaded “snippy” shears are by far the fastest tool for the job.

Wiring:

A selection of bonsai wiring tools, from left to right: Wire cutting scissors, heavy duty wire pruners, strong tweezers and wiring pliers.

Wiring is most commonly done in the late autumn, with the wires being left on through the winter and removed in the early spring. Again, I’ll add a full “how to” guide in a later blog.

• Wire cutting scissors (left) - these are easier to handle than the wire cutters, and will cope with wire up to about 3mm thick. The blunt ends make it easier to remove wire from the tree without damaging the bark.
• Wire cutters (second left) - these wire cutters were manufactured by the iconic Japanese Masakuni tool companyand are probably older than I am! These are a very sturdy pair of cutters and will cope with the thickest wire that is used on bonsai trees.
• Sturdy tweezers (second right) - another appearance of tweezers, this slightly sturdier pair often get used to manipulate fine wires when I am wiring twigs right to the tip.
• Pliers (right) - another tool it should be possible to get from a DIY store, I suspect these are of Chinese manufacture and didn’t cost me a great deal. These are used to manipulate the thicker grades of wire during the initial styling of bonsai trees.

A variety of different gauges of anodised aluminium wire; these run from 0.8mm through to 6mm. I most commonly use the smaller gauges up to 3mm, with the thicker gauges only usually being used when a tree is being styled for the first time.

- Richard -

Hi, my name is Richard Kernick and I am Kew’s bonsai specialist. I’ve been working at Kew Gardens for seven years, caring for Kew’s bonsai collection and also working part-time in the Alpine unit. In this first blog, I’ll introduce the Kew bonsai collection and provide a short history of how the trees ended up here.
 

Bonsai trees in the public display house showing autumn colour. Acer palmatum (approx 100 years old) in the foreground.

In the great scheme of things, bonsai have been a relatively recent venture for Kew. We currently hold about sixty mature trees, ten of which are on display at a time in a glasshouse situated near to the School of Horticulture and the student vegetable plots. I aim to display whichever bonsai are looking at their seasonal best, and those which have flowers, fruit or autumn colour might only be on show for a few weeks each year. The bonsai display house is open all year round with conifers and evergreens being shown in winter, alongside their leafless deciduous cousins. I work on the rest of the collection “behind the scenes” throughout the year, preparing them for their moment of glory!
 

A view of some of the bonsai trees kept "behind the scenes". Rhododendron 'Haka tahaku' in the foreground.
 

The core of the Kew collection of bonsai trees is based around the kind donation of Ruth Stafford-Jones. Ruth initially loaned a group of her trees to Kew during the 2001 Japan festival, and afterwards decided that she wanted them to be housed somewhere where they would be regularly seen by the public. In 2002 she donated fifty bonsai trees to Kew which were initially cared for by the Alpine unit. Sadly, Ruth passed away last year.

Since Ruth’s initial donation, other trees have been added to the collection. In 2005, three historic bonsai once owned by the famous iris grower Gwendolyn Anley were added to the collection. I'll talk more about this in a future blog post! Following Kew’s assistance with the Japan Car exhibition at the Science Museum 2008/09, we received a gift of a camellia bonsai, and were able to purchase four other bonsai trees from Windybank bonsai.

Thanks for your interest. In my next blog I’ll introduce the “tools of the trade”.
 

- Richard -