- Reaction score
- Vancouver Island, British Columbia
- USDA Zone
It is tempting to give a set of instructions because that is what is expected and it should be simple, right!This is the conundrum I came up against--I know that you're not supposed to bare root conifers because of the micorrhizal relationship, but if you're not supposed to bare root it, and not supposed to leave nursery soil in there, what do you do?
Well it is not always simple and there is no one right way. It depends on the tree's condition, It depends on the condition of the roots, It depends on the current soil and the change you wish to make to the soil.
Re potting is one of the fundamental skills required for successful bonsai care! When you watch a video the steps taken are basically what is applied in those circumstances for that tree, or a demonstration of basic principles that need to be adapted for specific circumstances. Conifers require more care and patience, they do not respond as easily or quickly from root work when compared to deciduous.
Having said that I will give you a general approach to the circumstances you are likely facing.
Acquiring nursery trees that are root bound and have been up potted for several years. They are typically in organic soil with tangled root ball and housed in narrow deep black plastic pots. You have been working with juniper as I understand it from your notes! Juniper react strongly to extra root pruning so it is important to balance your approach. In this case I advise the following.
Organise the following materials. Chopstick, scissors, bonsai soil you wish to use and a variety of pots typically wider and a bit shallower than the nursery pot the tree came in. The exception will be if you wish to grow out the tree and then you may wish a larger container and that is a separate process.
* Misting bottle to hydrate the tree and exposed roots during re potting! ( stop and do this every ten to fifteen minutes)
Adapt you approach if the you observe the following.
A. weak areas of root growth or areas of damaged roots ( in this case deal with this areas first counting the area as part of the allotted amount of work each session)
B. lack of feeder roots, excess strong roots with lots of feeder roots on the ends ( cut fewer strong roots, fold under those possible and wait for the tree to strengthen again before dealing with more stronger roots. If cutting a stronger root leave some side roots on the portion remaining, do not cut all the way to the base. With experience you will adjust your level of comfort and understand how much is too much! In the beginning err on the side of caution.
1. Dig carefully around the base of the tree and remove the soil down to the level of the main lateral roots coming out of the trunk. You are establishing where the base of tree is and exposing the nebari. When you are doing this use a chopstick and pull it outward from the trunk to the edge of the root ball slowly to gradually straighten small roots and remove the soil. Stop when you are at the level of the nebari. This prevents you from removing too much soil from the bottom first when the tree may be buried deeper in the pot.
2. Turn the tree over and using the chopstick carefully work out the bottom roots and soil for the bottom 1/3 of the remaining root ball. cut off the thick downward roots. When cutting the roots go back to side roots on the thick root wherever possible. leaving the side feeder roots intact. Leave finer flexible roots intact and to fold under when repotting. Set the tree back upright!
3. Using the chopstick with a slow outward and downward motion draw out the roots on the outside 1 to 2 inches perimeter. removing the soil and teasing out circular or longer roots. These roots will be cut to fit into the chosen container.
4. So for this first repotting stage you are removing soil down to the nebari. removing soil from 1/3 of the remaining rootball at the bottom and some off the sides.
5. Choose a container to fit the remaining root ball after these steps and prepare it for repotting. You want a reasonable fit with the depth to have some soil below the tree and approximately 1 inch around the perimeter. Tie or wire the tree in firmly when repotting, this is an important step so the new feeder roots are not constantly damaged by movement in the early recovery stages.
5. After repotting thoroughly water the tree until the water runs clear out the bottom, place in partial shade for three or four weeks. water when the tree needs water, but do not let it dry out and protect it from drying winds.
The next two repots will be 1/2 HBR, one side at a time. The process will be completed by the third repot and future repotting will be much simpler and involve different steps as the root ball changes to a more refined mass of feeder roots over time. ( for collected trees or finicky species I often divide this portion into three stages dealing with weak segments first) This is a slow but safer process I prefer for Mountain Hemlock and Shore Pine.
Typically, if the tree responds very well, one can complete this process over a period of twelve to fifteen months. First step in March/April, Second step in August/September and the last step in March/April. However juniper can be finicky and sulk after repotting so the tree may respond slowly and the process could take three years. ONE OF THE MOST IMPORTANT THINGS YOU NEED TO ACCOMPLISH IN BONSAI IS ADAPTING THE ROOTBALL FOR LIFE IN A BONSAI POT, THIS TAKES TIME AND IS THE FOUNDATION FOR A HEALTHY TREE TO DEVELOP AND REFINE OVER TIME.
Please note: I deliberately did not state what soil mix you should use. I am not aware of your climate or watering routine. My personal choice would be APLG. Akadama, Pumice, Lava, Granite. I would vary the percentage of akadama based on the climate. For medium and large trees I use a thin drainage layer of larger pumice one or two particles deep. The particle size of my mix is consistent for all components not that much smaller than the drainage layer so there is no concern over " water table". I prefer the extra air space for gas exchange in the bottom layer and most trees do not like to sit in water. For this reason I also select pots or containers with adequate drainage for healthier trees.
For those inquiring minds I use the granite grit for additional stability as pumice, akadama and lava are lighter components. Organic fertilizer is my go to for this inorganic substrate.