Species Specific > Japanese Black Pine Bonsai Discussion

Twin Trunk JBP -- Raw stock

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Adair M:
If your tree is sick, and you suspect poor drainage, I would remove the surface moss.  Thick moss looks good, but it doesn't do anything for the health of the tree.  I know we see pictures of beautiful trees at the shows with a thick layer of green moss, but that's for show.

If you think you need something to keep the soil from moving around when you water, use chopped spaghnum moss.


--- Quote from: Adair M on March 06, 2013, 07:16 AM ---If your tree is sick, and you suspect poor drainage, ...If you think you need something to keep the soil from moving around when you water, use chopped spaghnum moss.

--- End quote ---

should have specified, that is what i did use, chopped sphagnum. The tree did have poor drainage but also pretty exposed roots, so i did very light root work and repotted it. it was still planted a little high in the pot so i put some moss around the base at the roots                                                   

Leo in NE Illinois:
Wayne - to my eye, the twin trunk tree is not looking vigorous, but it doesn't look like it is in 'crisis' mode. If the soil is not real bad, gently combing out the roots on the outer margins, knocking off the underside soil where there are few fine roots and then potting up into a much larger pot for development and growing out would be what I would do. This may mean you replace 70 to 90% of the old soil. Do it  in spring and don't worry about it.

More generally,

I would not worry about the often touted but really not science based 'rule' about only removing 50% of the soil. It is based on gardening myth. When a tree is in crisis due to bad soil, and only 50% of the soil is replaced, you are guaranteeing that the roots in the remaining 50% will continue to die. For a tree who's health is on the decline, making sure half its roots die while waiting for another re-potting simply does not make sense. Where this rule came from does not seem to be based in logic.

Trees with healthy micorrhizae have fungi that has penetrated the outer protective layers of the older roots. You can bare root these and quickly the mycorrhizae will recolonize the soil. Using a spore innoculant can also make available micorrhizae. Keeping a small part of the old soil, as little as 1 to 5 % also supplies plenty of mycorrhizae. So the micorrhizae is not a justification for keeping bad soil. Where a pot has visible mycorrhizal mats, just peel a few off the old soil mass and work them into the new soil.

You do want to preserve what healthy root tips you have, so when you repot, don't knock all the old soil off, leave the soil particles firmly attached to the fine feeder roots you have. Comb out soil from the interior of the root ball where there are no fine feeder roots, this area can be cleaned fairly completely. Then replace as much of the bad soil as possible with good soil. As long as you keep as many as possible of the fine feeder roots undamaged, you can get rid of as much bad soil as possible, and if this works out to a 80% or 90% bare root, the tree will thank you for getting rid of the bad soil.

If the soil is not bad, then you don't have to get rid of as much. The only time I would leave 50% of the old soil would be if the old soil was in good condition, and the tree was healthy and vigorously growing. You would have to ask yourself 'Why repot if the soil is good and the tree is growing vigorously?" If re-potting at this time, it most likely would be for design reasons, to put the tree in a better pot for exhibition. This is the only time I would leave 50% of the old soil. Otherwise I would either put off re-potting and let the tree grow until the soil is starting to break down and the tree's grow rate starts slowing. Then it is time for a repot and a 70% to 100% soil change.

Colin Lewis and some others recommend not re-potting pines every year. The most frequent you would want to repot is every 2nd year if there was a lot of vigorous growth. Most pines once every 3 years should be the shortest re-potting interval for fast growing trees like black pines.

Colin recommends repotting only once every 5 to 10 years for slower growing pines like mature ponderosa pines. The tree in discussion was over 100 years old, so that particular old Ponderosa pine should only be repotted once a decade, or whenever the soil no longer allowed water to penetrate, which ever comes first.

Key is that soil condition drives repotting interval. If your soil becomes compacted and no longer allows water to penetrate in less than 5 years, you need to change the mix used for soil. You don't want to have to repot pines too often. They need 3 to 5 years in a pot to get some development time in. Most pines do little the year following a repotting. They only pick up growth the second and 3rd years. If you repot before growth has picked up you are missing out on growth and slowing down the development of the tree, annual repotting could possibly endanger the health of the tree.

These are my thoughts. You may or may not see it my way. I do grow in zone 5b, so I don't have as long a growing season as you do, so I need to get the most out of my growing season as I can.

John Kirby:
Leo, you do this? I realize it us uncomfortable for some folks, but repotting this tree now is one of the few things that can save it. Youd advice us of limited utility. If you live in Scotland, or in Maine, you can wait ten years on JBP. If you live where they grow well, this won't work. Repot trees in development moderately frequently, old established trees, less frequently.

Leo in NE Illinois:

--- Quote from: John Kirby on March 07, 2013, 09:01 PM ---Leo, you do this? I realize it us uncomfortable for some folks, but repotting this tree now is one of the few things that can save it. Youd advice us of limited utility. If you live in Scotland, or in Maine, you can wait ten years on JBP. If you live where they grow well, this won't work. Repot trees in development moderately frequently, old established trees, less frequently.

--- End quote ---

I thought I did say the tree looks like it needs to be repotted. I thought I also said I thought it was a bad idea to keep 50% of the old soil. The tree should have the majority of its soil replaced. The confusion may have come from akward phrasing, I was trying to say that I am looking at a photo and really can't tell how bad the soil is from a photo.

Yes, if this tree were mine, and I were certain that bad soil, decomposed, compacted soil that was no longer allowing air to penetrate was the cause of the poor root health, I would repot the tree and I would replace the bulk of the soil. I would work slow and try to not disturb areas where there appeared to be live and growing root tips. But everywhere else I would remove the bad soil. It does not make sense to me to deliberately leave bad soil on the root ball just because of some 50% rule. If I could do it without breaking too many root tips, I would bare root the tree, but generally it is better to leave a little around clumps of healthy root tips, but I would not leave more than maybe 10% old soil.

That would be my solution for a tree in crisis. For a healthy tree, I would delay repotting until after I start to notice that the pot is not draining as fast as it used to, or other signs that the soil is beginning to break down. If the soil remained in good shape for 5 years or longer, then I would not repot the tree for 5 years or longer unless the tree was clearly out growing the pot or a design reason required repotting sooner. If the soil stayed in good shape longer, and the tree has not outgrown the pot, I would leave it alone. One 'design reason' for repotting is to correct issues with the nebari, another is to change planting angle, another is to put it in a better pot. So I am not saying the rule is a rigid, never repot in less than x number of years, but I am saying, if you don't have a reason to repot, then don't repot just because the books say repot every year or repot every other year.

If the soil deteriorated some, I would repot right away at the next acceptable time period for repotting in my local growing conditions. If the soil has deteriorated badly, threatening the health of the tree, then do an emergency out of season repot if it were truly an emergency.

The tree Wayne posted images of does not look like it is in great shape, but it does not look to me like it is in catastrophic crisis. Without the tree in front of me I am only guessing, only Wayne or someone who has had 'eyes on & hands on" the tree can really make a firm statement about what should or should not be done with Wayne's tree. So I advise Wayne to not accept my advice blindly. He needs to decide what advice really applies to the problem tree in front of him. We are all commenting about impressions from an image and description of a tree, which is not the same as seeing the tree in person.

3rd point. The discussion about repotting pines too often comes from a discussion with Colin Lewis. Colin grows in Maine, I grow at the Illinois-Wisconsin border. Our climates are much more similar to each other's than to your climate. The tree that brought about the discussion was a 150+ year old Ponderosa Pine. But Colin extended the discussion to pines in general, and my group (as this was an 8 person workshop session with fellow Wisconsinites) was in general agreement that JBP in our experience did not need the frequent repotting often described by others. Here Japanese Black Pine is not the vigorous rapid growing tree that more southern growers describe. Up here JBP grows only slightly faster than Scotts pine. So this is the source of the advise I thought I would pass along.

The Ponderosa that Colin Lewis and I were discussing had last been repotted 6 years ago, and he and I felt comfortable with putting off repotting until next year, 7 years in the same, mostly inorganic soil. The potting mix was still draining well enough, it had not broken down. The tree was still showing good health, back budding and other signs of vigor. So no need to disturb it this year. So yes, I am extending the amount of time between repotting, as I offered in the part of my advice that was in reference to healthy trees.

While I have dabbled with bonsai for nearly 40 years, my first 25 or so years I was self taught and of course that means I never really learned much.  ::) In the last ten years or so I have learned a lot from teachers like Ted Matson, Colin Lewis, Marty Schmalenburg, Jack Douthitt and others. The JBP I have had the longest has been in my care about 18 years. This tree did suffer when I repotted it yearly. It did best when the interval was longer, about every 5 years seemed right in my situation, and I might see if it works letting it go longer. But I am growing MUCH further north than you are. My growing season is at least 40 to 50 days shorter than yours. Right now I get about 170 days frost free. Because I am close to Lake Michigan, some years my spring is very late due to cold winds off the lake. Last frost may be as early as April 25th, but I might not have a daytime high temperature above 50 F until middle of May. My redbud tree, which is a landscape tree,  has held onto flowers as late as May 25th, because the cold wind off the lake will both protect me from late frosts and also hold temperatures down, 10 to 20 degrees colder than a mile or two inland. Trees don't leaf out quick & candles don't elongate quick when daytime highs stay at or below 50 F. So perhaps I should not have offered any advice due to my somewhat unique micro climate.

I offered my comments about extending the time between repotting as an attempt to pass along an 'aha' moment, when the advice from Colin Lewis about not repotting pines too often 'clicked' with my experience.  I neglected in my passing this along to temper the comment with "from one northern grower to another northern grower".

But yes, I am following my own advice, and so far so good. But I also acknowledge that I do not have any trees of quality to point to. I am not an expert. Perhaps contact Colin and see what his comments are directly. He at least has some high quality trees that he has turned out as proof of his success.

Re-reading what I have typed, I am afraid I come off as being defensive. Not really the way I would like to sound. On the other hand, the above is my thought process behind my earlier post. I think in the future I will try to remind myself to step away from the keyboard. In person I am not as cranky as I might sound in this post, ..... really.  ;D


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