Japanese maple repotting

It's been a winter with mild temperatures and a lot of rain in southern England. Some of my maples have already started budding so I began to do their repotting sooner than I had planned. These maples seem to begin their summer growing based purely on average temperature.

The inspection of the roots is important. Soils and growing conditions are of great interest to bonsai growers - as you can tell by the number of opinions on soil mixes out there. It is also an opportunity to get hands on and fiddle as opposed to sitting back and watching them grow ever so slowly.

My maples are grown in the classical Japanese method of graded layers of Akadama. A coarse drainage layer topped with finer particles for the roots. This is the technique I have seen in many of the old Bonsai Today magazines which had translated articles from old Japanese nurseries. I am deviating now by using a drainage layer that doesn't degrade and introducing more ingredients into the main body of soil that won't degrade.

I suppose a few hundred years had taught them how to grow maples in an optimum fashion with Akadama. They do write a great deal about how the roots effect the branches of the plant above - so I'm hoping that my root ball full of lovely fine evenly radiating roots is going to give brilliant foliage this year.

Overly strong big thick roots can result in some parts of the foliage getting too vigorous and giving excessive inter-node length.

It seems to me that as the number of buds was increasing that the inter-node length was getting shorter.

They advise adjusting the drainage layer to suit the amount of watering and fertilising - my use of liquid fertilisers will alter this old advice as the soil won't clog up with organic debris. I have also read that some no longer bother with the drainage layer. I am still going with a layer of coarse baked clay on the bottom of all my pots.

Its pot was well shaped internally and after the wire was removed it came out very easily. The condition of the roots on the sides of the pot were not brilliant. This maple had been standing outside in the winter with no protection from frost or rain so this may be the norm.

This one was grown over a coarse drainage layer of Biosorb. The two distinctly different substrates made it easy to cut back the base of the roots to just below their old level.

Once the roots were out of the pot they were untangled and combed out - any crossing or thick roots were trimmed back( there were not many of these ). The roots were now in good condition as they are already been straightened out from previous repottings and were radiating out evenly. A few new surface roots were running circles around the trunk and were removed. The tree had been in this soil for 2 years and was ready for a trim. I did clean the bottom of the root ball as well - happily there was not much there other than lots of fine roots.

Most of the old soil is removed. This was 2 line Akadama after 2 years outdoors - I saw very little degradation of it.

This maple is now coming into its 7th year with me. The trunk is 6cm thick and the roots above ground at 12cm. It is starting to look very attractive. It is also developing a rather nice bark.

I am gradually moving away from Akadama so this is about 50% Akadama and 50% Fuji volcanic grit. I am only using Fuji volcanic grit because its what I have on hand that won't degrade - any other hard modern substrate will suffice. All the substrate is mesh graded and dust free. In addition I have added a large helping of rootgrow to help it along. I have found that this gives the maples a good deal of extra energy.

I will continue to grow these with Canna nutrients. This year I will use the Hydro Vega product which is for run to waste hydroponic systems using inert substrates ( basically what I'm doing with bonsai ). I did also apply Rhizotonic to when I gave it its first watering to help the new roots along.

The first leaves are out ( repotting timed perfectly ) and I expect the maples to be in full leaf by in another few weeks.

Winter repotting observations

This is my first beech. It is pioneering the techniques that I will use on the other bigger ones in years to come.

http://englishbonsai.blogspot.co.uk/2012/04/first-copper-beech.html

In 2012 it was the smallest and least interesting beech - and now it is almost the largest and very interesting - at ground level the trunk is now 5-6 cm diameter. There is a good taper in the trunk and some gentle movement. I have never seen a wild beech tree that looked like a deep fried pigs tail - so the gentle movement is just right.

The difference in growth rate and quality of foliage may be partly due that the big pots being on tap water and cheap bulk fertilser whereas this one has been on rainwater and Canna Bio Vega.

Santa brought me some nice sundries - more soil stuff and some training pots - so that the trees that were in training could be re-potted into bigger and better pots.

This picture as I pulled it out of the pot today (28 Dec) seems to show that the root system is quite busy underground in mid winter. Well it has been a very mild winter so far but I'm still surprised.

This soil mix has worked very well and the tree has really done very well in it. In retrospect adding the bark to the otherwise inorganic growing medium was a good idea.

Beech trees in their native forest habitat are dependant on mycorrhizal fungus for their nutrition. Their metabolism seems to be set up that way - so I am doing it in miniature in pots. This beech has had several flushes of growth this year and needed a lot of cutting back - especially the apex - the other beech trees just give me a single flush.

This is the growth medium I am using this time. 3 parts of biosorb + 3 parts supalite + 2 parts bark - none of which were filtered or graded. The biosorb particles are a bit coarse so the smaller supalite particles bring down the average. As you can see in a later image the roots have done very well in this fine average particle size medium.

And the pink soil is ugly. In retrospect the bark addition is the important bit as it gives the natural fungi something organic to cling to. And as I have been exclusively using organic fertilisers for the last few years it is vital to have all the soil micro organisms present to get the nutrition to the plant.

I am lining all my pots with these coarse clay pebbles as a drainage layer. These big plastic training pots are 32x45x16 cm. I fill them to within about 1 inch of the top to make them nice and easy to water.

I was very happy when I saw these roots. Lots of fine roots. All I did was work the edges of the pot loose and trim some thick roots out. There wasn't much to do as I had a pot full of lovely fine roots.

Here it is back out on the bench. It's going to spend another 2 years in that pot.

While I was out there I decided to re-pot another of the trees. It's a field maple that I collected several years ago. I had been ignoring it as they seem to have a strange growth habit - and I was trying to understand it - there were odd bursts of growth and then long periods of dormancy. It was potted in pure biosorb.

It was in an old ceramic pot that was slowly disintegrating in the winters here. The most important thing here is what is living in the bottom of the pot. It is teaming with fungus gnat larvae - alive and wriggling in mid winter and weakening the tree for the spring. I am certain that this is the reason for the odd growth habit - it was under constant attack from pests in the soil. It also wanted more food - and it had quite a good year because I put it on the same feeding rotation as the big pine trees.

This is the field maple with all the thick roots removed and trimmed back to the coarse drainage layer. Nothing to complain about here. I'm hoping that next year I will do a lot better as the feeding will be right and the pests will be removed.

Not a great image - and it's over potted - but I'm hoping for 3 years in that pot and then a decision on its future. It will be pest free and very well fed. I'm thinking that the trunk will at least double in diameter over that time. As I hadn't cut it back much its branch structure is full of strange tapers and odd shapes.

The important observations from this session of re-potting are.

Natives grow very well in a finer particle inorganic mix.
Adding an organic particle to the substrate is important - especially with organic fertilisers.
Pest prevention in the pot is essential - fungus gnats are a real problem and difficult to cure.
Trees in a sterile substrate need a surprising amount of feeding to thrive.
Trees in training must be groomed constantly.

Big pot growing experiment

In early April I planted a few trees into giant pots, as an alternative to field growing as I don't have my own garden to dig up and experiment in. This is the result after the first year. 

http://englishbonsai.blogspot.co.uk/2013/04/move-on-up.html

I have been putting wire around the trunks as a Dendrometer so that I could have a good idea of the growth. Next year when they are settled I will be more scientific in my observations and keep more regular measurements.

It seems that the strong growth of wood begins in early April and ends in early September - before and after that there is still a lot of vegetative growth. This is outdoors and will be different under glass - early budding maples in cold shelters will have their major expansion earlier in the year.

Next year I will be sure to regularly water and fertilise during this critical period of growth (March to May). On established bonsai this is the time to go easy on the feeding to avoid big leaves and fat shoots.

This is an early August picture of the base of the oak tree. There is some good expansion already.

It already has a nice taper and a little movement in the trunk so it's not like a lamp post. I don't see many oaks with much movement in the trunk growing in the fields around home so I see no point in an oak bonsai that looks likes a pig's tail.

This picture was taken in early December after the leaves had dropped. I used a match box for scale (which is 5.5cm wide). There seems to have been another bit of growth since the previous picture. This is no surprise as it had been very active above ground.

The beech expansion was less impressive but still good. Its already quite a lot bigger than the oak - I think its a year older.

The beech does seem to want a little time to settle into its new home before it really gets going so I hope for a strong showing next year. My previously repotted beech trees have shown a pattern of growing a lot better in their second year. I suspect that this is due to the fact that the beech root system begins its growing after the budding - so potentially the new growth is a bit starved in its first year.

Given the behaviour of the root systems it is my opinion the trees must be potted and settled by mid March.

On both of these trees (especially the oak) I have been constantly pruning to keep their apical dominance at bay. I am specifically encouraging the lower side branches on both.

So far it all seems to be working.