Bonsai Step Five Transplanting & Root Pruning
All bonsai pots have holes cut in the bottom. These holes are usually about the diameter of a quarter and allow excess moisture to escape from the pot. Plastic screen is used to cover the holes and contain the soil. This screen is held in place by a wire “hairpin” which is passed through the screen and the pushed through the bottom of the hole. The protruding wire is then bent up on the bottom and prevents the screen from moving off of the hole during the potting process. Once this has been done a longer length of wire is cut and bent at two right angles.
This is then passed through the drainage holes from the bottom of the pot and as close to the inside edges of each hole as possible. This “tie down” wire will be used during the potting process to secure the tree in it’s container. The process, thus far, is known as “prepping the pot” and must be done before any work on the plants root system is started. Likewise all necessary soils and components needed in the transplanting process should be ready and immediately available.
The reason for all this advanced preparation is simple. The root system of any tree is it’s most delicate part. Great care must be taken to insure minimal dam- age to it. Unnecessary or prolonged exposure to the air can cause irreparable damage to delicate feeder roots. Therefore, the objective is to complete the root pruning and transplant process in a thorough, but efficient man- ner and minimize the amount of time roots are exposed to the air. Having everything ready and in place will help accomplish this goal. If roots should start drying out, keep a hand mister available and spritz roots with room temperature water as needed.
(The creation of a section of deadwood (jin & shari) near the base of the trunk helps to make this bonsai look more ancient.)
Carefully remove the juniper from its growing con- tainer and take a moment to examine the root mass of the plant. Learning how the plant grows and responds to dif- ferent kinds of outside stimulus is one of the keys to your success in bonsai. Unlike the upper portions of the bonsai, the roots aren’t pretty, but keeping them happy and in good condi- tions is critical to keeping the rest of the bonsai healthy and happy. Most container grown plants produced for the indus- try are planted into a mixture of bark chips and sand gen- erally called “growers mix.” This juniper is no exception. Look for tiny white root tips growing at the bottom and on the sides of the root ball. These white root tips indicate a healthy, happy root system that is actively growing. Next, try smelling the root mass. If healthy, it will have the wonderful odor of fresh turned garden earth after a spring rain. If the root mass has been too wet, it may smell a little like rotten vegetation and you will encounter slimy or decaying roots in the mass. Bad roots should be cut out.
The amount of roots which may be removed during the initial transplant process will vary greatly based on the variety of plant material being used and the time of year in which the transplant takes place. The general bonsai guideline regarding root pruning states that: For temper- ate plant material, transplanted in the springtime, just as the plant is pushing out new buds, it is always safe to remove a third of the root system.
(Begin by gently removing soil from the root mass.)
(Cut out thicker heavy roots and preserve fine feeder root)
It is a good rule, but you will quickly learn certain species will put up with even more drastic pruning if done at the right season. This juniper is a good example. The transplant was made in the springtime, just as the buds were emerging. Junipers are vigorous growers and so there was not hesitation in removing slightly more than 2/3 of the root system. If we had chosen the hotter months for the transplant we might have only taken half of the root system or less. You want to make sure that you don’t remove so much root that the tree will have problems sup- plying water to the foliage.
Using a chopstick, root rake or your hands, begin to gently remove soil from the roots. You will notice that a great number of roots will be located near the edges of the pot and at the bottom, and that the interior of the root mass will contain fewer roots. Water drains towards the bottom of the pot.
(On junipers it is usually safe to remove from one half to two- thirds of the total root mass if done in the springtim)
The roots simply go where the water supply is best.
Remove most, but not all of the soil. Leave some soil in the root mass near the base of the tree. Using a pair of sharp shears, remove about 2/3 to one half of the juniper’s root mass. Examine the roots. You will find two types: 1.) Large heavy roots used to anchor the tree in the earth, and 2.) Fine feeder roots used to take up water and nourishment. Feeder roots are our main con- cern.
You will be tieing the tree into the pot with wire and will not have need for the heavy anchor roots. Remove them. Remember to move swiftly through this process. If fine feeder roots begin to dry out to spray them with a little water.
(Above & left: The tree will be tied into the container during the potting process. This is accomplished by running a copper wire through the drainage holes and up into the inside of the container.)
Soil
The soil into which you will plant your juniper should be of a type generally used for bonsai. To the newcomer, most bonsai potting mixes resemble a composite of rock and gravel with very little organic material. Such a loose composition is critical to the development of fine feeder roots necessary to insure the plant’s survival in the limited space of a bonsai container. You may obtain ready made bonsai soil from deal- ers or you may choose to do a little research and prepare a mix of your own choosing. In no case should you repot it using the growers mix or with the heavy black soils sold by most nursery outlets. The correct mix should be very granular and well draining with particle size ranging from one quarter to one eighth inch in diameter. Place several scoops of bonsai soil into the container, mounding it in a pile near the center. Next take your freshly root pruned juniper, comb out the roots a little, shake off any loose soil chunks that are clinging to it and place it on top of the soil mound in the pot. It is best, for artistic reasons, to plant the tree slightly off of center. Rotate the soil mass left and right and press downward. As you do this, it will force soil up and into the under-
(Position the tree on top of the soil mound and slightly off center.)
(Once the root mass has been snuggled in the soil the root ball is tied into place with the copper wire. )
Soil may now be added to the container. A chopstick is used to work soil in and around the exposed roots side of the root mass. The base of the tree should be just slightly above the top rim of the container. Make sure the tree is positioned at the correct angle and does not look off balance in the container.
(Soil may now be added to the container. A chopstick is used to work soil in and around the exposed roots.)
Next, bring the two ends of the tie down wire across the top of the root mass. Using a pair of pliers, take out any slack in the wire and twist the ends of the wire to- gether securing the root mass in place. Make sure during this process you do not pull the drainage screen off of the holes in the bottom. Clip the ends of the wire off and bend the sharp points into the soil mass. This wire is only necessary to keep the tree from tipping over for the first few months. Once the roots have had the opportunity to establish themselves you may clip the wire at the surface and pull it out through the drainage holes.
Next, comb out the roots a little more and begin adding bonsai soil to the container. The objective here is NOT to make a root sandwich, i.e. - a layer of soil, a layer of root and another layer of soil. Rather, you should use a chopstick or wooden dowel sharpened to a point and work the soil in and around the roots. The soil mix should be bone dry in order to facilitate this process efficiently. Chopsticking soil around roots can be tedious and time consuming, but it is critical to the future health of the plant. There is no room for air holes in a bonsai pot... only roots and soil. Take care to fill all the vacant cavities with bonsai soil. As you wiggle the chopstick back and forth, press down with your finger tips to feel the surface of the soil. You will discover you can feel those areas in the con- tainer that need more soil. Once you feel that all air pockets have been elimi- nated and that soil has been properly worked in between all the roots, you may use a brush to sweep remaining soil down to the edge of the pot. At this point any fine roots which are sticking up out of the pot should be trimmed off with a pair of sharp shears. If not, these roots will expirate water and desic- cate the plant.
( After soil has been thoroughly work around the roots, all excess soil should be removed down to the rim of the container.)
(Any hair roots that protude above the soil mass should be clipped off otherwide the will expirate moisture which the plant needs )
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