Nuances of first repotting of nursery stock junipers

Here is a piece of nuanced information that I am starting to distil from the numerous nursery stock junipers that I got to perform the first repot from nursery container and field soil (among rocks, styrofoam, etc) to a bonsai container. What I’ve been noticing is that most root growth happens around the edges of the plastic container, perhaps because there’s better water flow and consequently balance of water and oxygen there than in the middle. If you go about cutting bottom, sides, etc just to cut the root mass to a size that fits into a pot you’ll be cutting most of what is worthwhile keeping. In the middle you’ll find among other surprises very little viable roots. Of course several of the roots growing on the edges originate in the center. So it pays to take the time and go slowly teasing away soil, rocks, styrofoam and the matted dead roots that make up a lot of the stuff there while gently maneuvering around, under, over the viable roots. In doing so, when it came the time to cut one or two thick roots, I knew exactly what I was removing. Of course I left a section intact and whereas I didn’t bare root it (i.e., I didn’t wash it off the soil), in this case I don’t think it would have been detrimental (see below the photo for the reason why). However, I think it is better to not do it even in a nursery juniper. In terms of tools, for 95% of the work, only patience and a single small pointy wood chopstick so you have the ability to go between roots on the edges and tease them away or the soil behind. At the end scissors/root pruners if/when needed.

As a result I managed to put the tree in a very small pot. I was lucky that there weren’t any major points of limitation. There was one thick root that I wasn’t comfortable cutting but I managed to bend it sideways.

As a side note, last year I experimented on a nursery stock juniper in which I fully washed the roots and in doing so I managed to do the first repot with minimal damage to the roots and the tree didn’t skip a beat. It is healthy, and growing.

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Good idea posting this. Others will find the tip “be patient” most useful when attempting to repot these sometimes frustrating pieces of material. I have a medium sized Sabine Juniper that I am waiting on. It is barely starting to show needles emerging. The weather here isn’t warm enough I don’t think.

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I was just given a persimmons juniper in nursery pot and soil last week that I’ll be repotting next spring, I definitely follow this advice. Thank you!

Good info, rafi…thanks. I have several to repot soon, so this will be helpful at that time. I’m curious about what mix you use. I seem to recall Ryan using a 1/16-1/4" mix of 2:1:1. Approximately how much can you reduce the root mass after you have combed it out in this way?
I do have a juniper with what seems to be a very dense root/soil ball, that I haven’t yet done anything to. Have you run into this type of situation, and can you make recommendations on how to handle?

I am not Rafi but…

I have a lot of experience with junipers that are root bound in a nursery pot. It is a difficult problem and as Rafi says use a lot of patience. Some examples I have seen on vids show people just taking a saw to the root ball. I do not advise this because as Rafi says most of the good living roots are near the edge of the pot.

In my experiments, the best way to handle a root bound juniper, or any conifer, is to go up the middle of the root ball from the bottom leaving a 1 - 2 inch shell. Most of the roots in the middle will be dead because of lack of oxygen and water penetration. Scrape the side of the roots to be sure they are dead. This can take a while. I use a chop stick and a hose with a trigger spray attachment. You can cut away anything that is dead. When that is done, I tease just enough to splay out the shell so I can get it in a shallow(er) pot. The outer 2 -4 inches of the splayed out root mass can have the soil teased out too. It is not advisable to reduce root mass in any significant way in this situation. Another important thing is to not cut any foliage away until the tree shows through growth and color that it has recovered.

There is one time I had a juniper so rootbound that the shell would not splay out. In that case I put it in a slightly wider pot and made holes through the top so I could get better soil down in the hole. I also put good soil around the sides. It took 4 years to get that one in a shallow pot.

For conifers, in general you want to fit the root mass you have into an as small a pot as the roots allow. Reducing root mass is mostly for deciduous trees. There are times it is done to conifers but it is much more rare and the reduction is selective to what an individual root is doing for the plant. Ryan has touched on this and Walter Paul says, in most cases, to find a way to make the roots fit in the pot.

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Thanks, ren_man. Two of these came from bonsai nurseries, so maybe they won’t be as compacted as they appear, but the more I can learn now, before the time comes, the better the process may go. I made the mistake this spring of picking a pot that appeared to be the correct size, and then trying to force the roots into it. I will probably lose that tree, and it is a yamadori from Todd, so an especially hurtful loss. I think maybe I’ll just have some lumber ready, and build a box as soon as I can tell what size it will need.
The tree you had that was so compacted it took 4 years to get into a shallow pot…how often did you repot?

thanks

In 2 year increments but the health was good each time. I did it in a very special way by cutting away half the pot so the 1/2 I did not work on remained fully undisturbed. I then used wire to hold the pot together. The first side I worked on, I did my best to choose the strongest side with the most roots. It lived and is still alive.

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Cool idea to cut the pot in half…I’ll file that away for future use! Thanks

Most of my material comes from “reduced for a quick sale” benches at regular nurserys. I like to get the trees out of the multi perpous compost in the spring and into a training pot of usually about the same size. This is because usually I need to heal a trunk chop, encouraged vigorous growth to get back budding or thicken the trunk. This half way house re-potting also gives me a better idea of what the tree will eventually end up in, as well as sorting the roots out. I have definitely fallen into the trap of forcing trees into tiny pots, just so I can call them “bonsai”.

I’m curious about the comment you made about not reducing root mass on conifers. I have a jbp in a grow box but have since decided that it would make a better literati than standard informal upright. But I’m trying to figure out the correct way to go about getting the root mass from the grow box to literati (very shallow) pot. Do you have any recommendations for how to go about doing that or does this mean it’s a no go to make it a literati?

Absolutely you can make a literati from it. Two ways to go about this.

  1. Put it in a pot that will fit the roots that you have. Not a loose fit, but a firm fit. Let it recover, then style it. The plant will not keep roots that the foliage can not support and then repot after it has adjusted to its’ new form. The plant decides what roots it wants to keep. Be careful reducing foliage, make sure there is a balanced amount of foliage on each branch so it has good reason to keep everything you want to keep. If anything, you want to keep more foliage toward bottom. Do not expect a couple of weak buds on a lower branch (or any branch) to sustain the branch. Make sure anything you want to keep is not shaded.

  2. You decide…get the back budding you want now by letting it grow then reduce foliage where it is now…it will get very vigorous but keep it in check. With good health, repot the next energy positive season and eliminate roots that do not have any or few fine roots first. The risk is you cut something the plant needed to sustain the foliage it has. Remember, a pine’s strength is in its’ roots. When reducing, I never take more than a third each repot. With pines, only one major procedure per energy positive season.

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