Bonsai pots

The rain is falling and the temperatures are finally increasing so it looks like spring is finally here. In the coming weeks once the buds have swollen with all that energy from the roots it will be time to repot some of my trees.

As you may have already seen many of my trees are in deep plastic pots, either because they were brought from a garden centre or because I planted then into these when they were dug from the ground. With some of the trees it takes time to prepare the roots to fit them into a shallow pot.

Once the roots have been prepared to fit into a bonsai style pot then the next step is to find a pot that best suits the size and style of the tree. Unfortunately it isn't so easy here in Finland. There are many places that sell bonsai trees, mainly malsai type in 15-20cm pots, but nothing else is available from these places. The only possibility to obtain different pots is to purchase these online from another country. There are many online shops in many countries supplying pots, tools and other accessories but the biggest problem with this is the high delivery costs when shipping to this part of the world.

With this in mind, and to cater for my own needs, I decided to start an online shop back at the end of November called "Raisio Bonsai and Garden" ("Raision Bonsai ja Puutarha" in Finnish) selling bonsai pots, tools and accessories. I understand that the demand here in Finland is not very high compared to many other European countries, and this has much to do with the population of just over 5 million and the harsh climate we have in this part of the world, but there is still a demand so the company has now become part of my interest in bonsai.

Even though my initial stock wasn't very big I still tried to purchase many different shapes, sizes, styles and colours of pots. I myself was looking for bigger pots than those that come with bonsai trees normally available in garden centres. This meant that most of my pots at the moment are 20cm or bigger, but soon I will be receiving more pots and many of these will be covering the smaller sizes.

Choosing the correct pot for you bonsai

Choosing the correct pot to achieve the maximum effect for your bonsai can be a challenging decision, especially when first starting to make bonsai. The basic guide below is my conclusion from many guides that can be found on the Internet and is what I try to use when choosing the correct pot.

Size of the pot depends on the size of the bonsai tree.

• Pot depth = Trunk diameter
• Pot length = 2/3 the height of the tree (Oval / Rectangle pots)
• Pot diameter = 1/3 the height of the tree (Round pots)

Shape and style of the pot depends on the type and style of the bonsai tree.

• Rectangular pots = Masculine trees such as Pines and big Maple trees.

• Oval pots = Feminine trees such as Maples (Japanese) and flowering trees. Oval pots are also suitable for forests or where the tree has many trunks.

• Round pots = Feminine trees such as Pines and Maples with tall narrow trunks. Style of the tree tends to be literati.

Colour of the pot depends on the class of the tree, masculine or feminine, and the type of the tree.

• Dark brown / Red / Unglazed brown = Pines and other conifers.

• Light brown / Creme = Maples and other similar tree types such as Birch and Oak.

• Green = Maples and other similar tree types.

• Light blue = Flowering species.

• Dark blue = Pines and Maples.

There are many different shapes, sizes, styles and colours of bonsai pots available that means that the mix of pot and tree could potentially be whatever. At the end of the day it is what you feel happy with and what looks pleasing to the eye, but I hope that my basic guide helps to give some ideas.

Still waiting for spring

Last weekend I decided to move my deciduous trees back outside as the night temperature had been only minus 2-3°C for a few days and the day temperatures a couple of degrees above zero. On this basis I got excited at the prospect that spring was finally coming, but sod's law that very evening the night temperature was then back down to minus 15°C.

Fortunately the trees are placed next to the house so I hope it wasn't too cold for them. All winter they have been in the garage and even on the heater bed I made, which was turned on when the temperature inside the garage got close to minus 10°C, and then in one night I could have undone all of my hard work. Even today the snow is still coming but I hope soon that it will change quickly so I can start to do the repotting jobs that I have planned before the buds start to open.

On most of the trees it is clear that the buds are starting to swell, but the buds on the Amur maple (Acer tataricum ginnala) are not yet showing any signs of swelling.

I hope that it is just too cold for them to start appearing yet and not that the tree has died. I like the look of this trunk and it would be a pity to loose it. This tree was repotted last spring so this year I was planning to cut back the long thicker trucks to develop more smaller brackets. I will do this in the next week in readiness for spring when the energy starts to transfer from the roots back to the brackets for generating the new leaves.

First casualty of the winter

This winter has been a very long and cold one this year and we are still waiting for spring to start, but I must confess that I have already had my first casualty of the winter period. Unfortunately this has nothing to do with the 50cm or more snow or even the -15°C that we have had for most of the winter. No this casualty is one of the trees that has been snuggled up nice and warm inside my house. The Fukien Tea tree (Carmona Microphylla) has decided that this was the time to go. I am unsure of the exact reason but my theory is that the untreated cut, which is common for malsai bonsai, was the start of it's decline.

As normal for this time of year the inside of modern homes are quite dry when there are freezing temperatures outside and this dryness means that there is very little humidity in the air. This, I believe, has resulted in this untreated cut drying out and then slowing working itself down the tree. The leaves from the higher brackets fell from the tree first and the lowest branch was last to loose its leaves.

I have a cutting of the Fukien Tea tree taken a couple of years ago from another tree that also died, but fortunately this is still growing well leading me to believe it died because of the untreated cut and not the dry air during the winter months. If anybody as any other reasons why my Fukien Tea tree died in this way then I would be grateful for the information.

More snow

This is the winter holiday (talviloma) week here in Finland and is traditionally the coldest week of the year. In the past few years this has not been the case but this year this has come back with a vengeance. We have had temperatures of minus 17°C for the past few days and more of the same is expected for the coming week. Along with the cold temperatures has come some more snow. We had already quite a lot and are now struggling to find a place to put it all.

At least the more snow helps to cover my Pine trees. I have not completely covered them because they are also positioned close to my house, even though I could easy do so with the amount of snow that we have had.

The deciduous trees are still in my garage on the heater bed. I have had this on a couple of times to relieve the temperature a little, but the good thing is that the garage is keeping the temperature some 8-10°C warmer than the outside temperature. As you can see I have placed some snow on the pots which will slowly melt into the soil to prevent the soil from drying out.

Winter protection

As mentioned in my earlier post the winter can get quite cold in Finland. We have recently experienced temperatures of -25°c only last Saturday. My bonsai (potensai) collection at the moment is quite small so I am able to offer more protection for the deciduous trees by placing them in my garage and on the heater bed I made, but the two pine trees I have left outside.

The pines, as with all evergreen species, require some light during the winter period as photosynthesis still takes place. I moved the pines closer to the house to get some protection from any strong winds, we could get during the winter, and to remove them from the direct sunlight that we can easily get on a nice winter's day. Exposure to direct sunlight during periods of sub-zero temperatures can cause damage.

When the first heavy snow fell I covered the boxes that the trees are planted in with the snow. This helps to keep the temperature under the snow a little higher than the actual outside temperature and protect the trees from any heavy frost. Now we wait patiently for spring to see if all of these various techniques for protecting the trees during the winter period have paid off.

Heater Bed

Winter in Finland can be quite cold with temperatures going down to minus 25-30°c. In the south of Finland where I live the temperature tends not to be so cold but can still easily be more than -15°c. These low temperatures mean that protecting the outdoor bonsai during this period can be a challenge.

I have a garage where I place the deciduous trees that will protect them from the frost and the cold wind, which is one of the main culprits for killing the tree because the wind can dehydrate the tree during this period of dormancy, but this does not protect them from the really cold temperatures. The garage already keeps the temperature a few degrees higher than the outside temperature and in general temperatures down to -10°c are ok but anything more than -10°c it is advisable to provide some extra protection. The garage has electric floor heating installed but this costs a fortune to keep on, as I found out to my horror last year when the electric bill arrived, so this year I thought I would build a small heater bed for the trees to sit on that I can put on when needed without costing a fortune.

The heater bed consists of a wooden frame with a thermal insulation base on top of which are two layers of sand. Sandwiched between the layers of sand is a heater cable attached to a metal grid.

The following photos show the step by step build of the heater bed.

Step 1. Wooden frame
A wooden frame was made as shown in the image below. The size of the frame was approx 120x60cm. The width of the frame matched the width of the thermal insulation material I would use. I attached a large sheet of plastic to the sides and bottom to help to retain the sand from falling through.

Step 2. Thermal insulation material
On top of the sheet of plastic I placed a piece of thermal insulation material. This material is about 4cm thick and very stiff. I could of used some type of board to form a firm base to hold the sand but this is what I had available and I thought it would help in maintaining some of the heat.

Step 3. Heating cable
The heating cable, which can be obtained from a local electrical shop, is specially designed to be used outside and for keeping things warm. Normal use of this cable is to warm water pipes, either the main water coming into a house or attached to drain pipes to prevent the water from freezing during the winter. The temperature output of the cable is approximately 10°c and uses 10 watts per metre. The length of cable I have used is 10m meaning that the power consumption is 100 watts. The cable is attached to a metal grid the size of the area with cable ties. I attached the cable on both sides of the metal grid at equal distances to try to get an even distribution of the heat. The cable is already fitted with a standard electrical plug as seen in the bottom of the image.

Step 4. Sand
The finished cable was taken out of the frame and a layer of sand approximately 2-3cm deep was added on top of the thermal insulation material. I then placed the cable on top of the sand and then proceeded to add more sand to cover the cable. I was not sure how much sand I needed so I started with another 2-3cm. The reason I wasn’t sure how much sand to add on top of cable was because I didn’t know how warm the sand would get when there was power to the cable. I wanted the sand to get warm but not to too warm and even though the temperature output was only 10°c the fact that I had looped the cable close together meant that the combined temperature could be more than that. As it turned out the difference between the ambient temperature and the temperature at the top of the sand was about 10°c. Because I am planning to use this heater bed only when the temperature is really cold the sand will never get above the magic temperature of +10°c, temperature that would start to represent that spring was here, so this difference is fine. If the temperature had been too high I would have simply added more sand to absorb more of the heat. In the image below you can see a thermostat to the left hand side. The thermostat takes the ambient temperature and a sensor, normally used to take the outside temperature, is inserted at the top of the sand to give some indication of the temperature of the sand.

Step 5. Placing the trees
We have been blessed that during November and the beginning of December the temperature had been quite warm for this time of year with temperatures even reaching +8°c on some days. But as can easily be the case here in Finland the winds change direction and we go from +2°c to –12°c overnight. This happen one night a couple of weeks ago and then that was the time to move the trees inside the garage and on to the heater bed. I didn’t actually turn the heater bed on because the garage was protecting the trees from the frost and the ambient temperature was only -6°c. Winter really started to come after this day with daily temperatures of –10°c to –16°c. During one of these days I turned on the heater bed as the temperature inside the garage was now –9°c. The out come was that the sand warmed to a nice temperature of +2°c. Perfect to keep the toes (roots) warm of my small collection of bonsai (potensai).

Cat litter as inorganic soil alternative

I mentioned earlier about my own bonsai soil mix. This isn’t as scientific as it first sounds. As many of you may already know bonsai enthusiasts throughout the world have been turning to cat litter (kissanhiekka) as an inorganic soil alternative to Akadama. Akadama is expensive and can be difficult to obtain here in Finland, often only available by mail order from another country. Cat litter is of course much cheaper and can be purchased from any supermarket. I have tested a couple of brands to establish if it retains its shape when wet and frozen and found that the brand ‘Rainbow Kevyt Kissanhiekka’ is the best cat litter that I have come across at the moment. I have used this cat litter for over a year for all my bonsai, indoor and outdoor, without any problems. The soil mix can be 100% cat litter if you require, but you can also mix it with other ingredients for specific tree types or to suit your own personal preferences. For example you can add some grit for a drier mix used on pines, junipers etc. or some pine bark to retain more water.

When using any material for bonsai soils it is important to remove the small particles and this is also the case with the cat litter. I have found with the brand that I am using that the largest particles are ok and remain in my mix but I sieve out the smaller particles less than 2mm. These small particles are not needed in the mix, as they will not allow the water to run through as easy.

My own bonsai soil mix has been made up of roughly 50% cat litter and 50% pine bark. The pine bark is also purchased from any local garden centre and then I run this through an old food processor to cut into smaller pieces. Again, as with the cat litter, I sieve out the smaller pieces and this time also remove the larger pieces that are bigger than 5-6mm. This bonsai soil mix I have used especially on my indoor bonsai because it helps to extend the time between watering that can be problem if using 100% cat litter.

Two of the most important tasks that need to be performed correctly for your bonsai to grow, watering and feeding, have been made easier by using cat litter.

Watering

Watering of my bonsai was a job that was a little difficult to understand in the beginning with questions like How often should I water? and What different watering schedules are needed for different trees? All this is now history when using cat litter. If required I could water my bonsai everyday, this can easy be the case in the summer, without any problems because any excess water not retained by the cat litter simply runs out the holes in the bottom of the pot or container.

Feeding

The use of cat litter has also changed how I feed my bonsai. As with the watering I was constantly reading about different feeding systems for different types of trees, but now I feed during the growing season every 10-14 days with a balanced feed knowing that the daily watering regime during this period will wash away any excess fertilizer before the next dose.

Conclusion

Cat litter is a cheap, easily obtainable alternative bonsai soil that will help to keep your bonsai growing vigorously with regular watering and feeding regimes.