It seems that each year since I started this column, over six years ago, that I have written about repotting in the Spring. Since repotting is such an essential part of our bonsai regimen, I thought that I would recap a few things and maybe pass on a few new tips. I just finished teaching several workshops specifically on repotting, with one more to go. Seeing a few common misconceptions, and some really good practices brought a few things to the forefront of my mind. I am sure that you are well into your repotting season by the time you read this. I started just last week – about March 1 on my trees.
The first point to consider that this is the only time that you get to work on the roots for at least two years. That is for deciduous. For conifers it might be 5 years. The work that you do now has to last the tree for that period of time. We have several times to correct branch structure by pruning, wiring, etc… during any one season. However, this is the only opportunity that we have work on the roots, correcting flaws, changing the soil or container and setting up the health and growth of the tree for the next several years. It’s worth getting it right, to the best of our ability and knowledge.
First and foremost is the aftercare, so I am starting at the end, rather than the beginning. Make sure that you can keep any tree that was repotted this season from freezing, or at least the root portions. It’s also best to be able to keep them out of the rain for several weeks until you see the tree starting to use up the moisture in the container. That means that it has recovered and is ready for the transition to our great Pacific Northwest spring weather. Rain.
For the first time in 30 years of bonsai, I built a heat bed to facilitate the recovery of plants after repotting. I mention the 30 years, because it is not in any way essential – I have made it fine this far. However, I can tackle the aging and declining root balls of some very old, collected trees with confidence. I started that process last year with great success and am now moving onto harder specimens That may be the subject of a future article. What makes my heat bed a little different is the fact that it is not in a greenhouse, but just out in the open on my patio. I love it already after just one week.
Next up is, have a plan. Do you have all of your soil components sifted and/or mixed and ready to go. Do you have the pots? More importantly, do you have the time? I am finding that just taking a pine from a six-inch pot up to an eight inch, with pruning, etc… is taking me about half an hour at cruising speed. I can’t seem to do a medium size tree in less than two hours. And since most of my trees are larger, you can do the math.
If you run short on time, wrap the root ball in a wet towel and finish it later – within a day. Or you can heal it into a mound of something you might have, like old soil, bark dust, etc… Just make sure that it’s moist. Once you have the tree popped out of the old container, work on the new one before you start on the root ball. The less time your tree is out in the air, the better.
If it is going back into the same container, take time now to rinse it out and let it drain and dry. If you know what pot you are going to use, put the drain screen in. The point really is to be looking ahead at what you are going to need to do to finish the repotting. Do you need to sift more top dressing? Do I need chopsticks of a different size? You get the idea.
My next point is to be gentle. Use a root hook only when necessary and with great care. Slow going with chopsticks or angled tweezers is much easier on the tree. The soil should be moist but not wet. Handle roots with care. You can decide later what to cut off, but if you mangle them, the choice is made for you. And remember that we don’t want to bare root a conifer. It’s chances of surviving, let alone thriving, go down really fast. Also remember that you don’t necessarily have to cut roots to fit them into the pot. If you feel that you need to keep more roots for the health and vigor of a tree, you can simply fold them gently into the pot and address them in another few years when you have more root mass to utilize.
What soil you use is quite the conundrum and I am always seeking to improve what I have for each tree. There is no doubt of the effectiveness of Boon mix for bonsai, a 1:1:1 mix of Lava, Pumice, and Akadama screened to between 1/16 and ¼ inch particle size. But it can be tweaked. And a lot. Take out the 1/8-1/4 for shohin, or the 1/16-1/8 for trees that like it a little drier, like mountain pines. But there’s more. I have mentioned in the past that we can to use up to 100% Akadama on deciduous trees. I am getting mostly favorable results with that – better than the standard mix.
But then there is Michael Hagedorn who favors just Pumice and Akadama, and our own Dennis Vojtilla that uses Lava and Akadama. They are leaving one component out and you can hardly argue their practice, looking at their trees. So, experiment on what works for you. I just had a workshop with the Eugene club, and their president, Tom Fincel (An outstanding bonsai artist and even better person to get to know) had a large container each of sifted Pumice and Akadama (A student of Michael’s) with which he could easy mix up whatever proportions he likes for any particular tree and I really feel myself gravitating to that approach.
The last thought that I leave you with is what was hammered into me (albeit it gently) by Boon. Neatness counts. It carries through the whole process. It starts with the preparation of the pot. Make sure the screens are fastened neatly into a clean pot. My screen clips are always oriented perpendicular to the front of the pot to offer the lowest profile, so no one sees them hanging down in a show. The tie down wires likewise, running front to back instead of side to side, which uses less wire and is usually hidden by the pot’s feet. I have to do all of this anyway, so it really is not any more time to make it tidy. Why would you tie a crooked tie, or leave your shoes half tied?
On a finishing note, make sure that you do not mound the soil too much. This is a consistent trait with beginners. Level off the soil where the roots start and taper it down to where you have a good ¼ inch lip around the edge of the pot. This not only looks good, but makes it so that the water stays in the pot when you water.
Happy repotting. Scott Elser
