Hi friends - hope you are all doing OK during this crazy time wherever you are in the world! (I’m in the UK here) I was wondering whether anyone can give me some advice with a pine I’m struggling with…
I bought a young Miwaka Japanese black pine in January that I want to develop into a neagari (exposed root) style tree. I’ve been doing bonsai for a while but this is the first pine I’ve had, and I have no idea how to treat them. So I bare-rooted it (probably a massive error), planted it in a tall tube filled with pumice and large gravel, and then planted the whole thing in an akadama colander. I also put some of the original compost in the colander to try to keep some beneficial fungi in the mix.
Well, sadly, the tree still hasn’t shown any signs of growth this year. I think it’s still alive (I scratched a branch and the cambium is vivid green under the bark) but the tips of the short needles from last year are yellowish and the tips of older needles are brown. I was wondering whether this could be because the plant is really stressed after bare-rooting and planting in pumice; maybe it’s using all its energy trying to grow them into better soil. Or maybe it’s something totally different, like a nutrient deficiency.
Has anyone had any experience with pines (or other conifers) being mistreated in a similar way and failing to bud out/displaying similar symptoms? Is there anything I can do to help the tree recover? I guess I’m just looking for some reassurance that I haven’t just completely killed it, though I guess it’s all part of the process…
To give some idea about the tree’s environment:
- Based in the UK
- I’ve been feeding the tree quite heavily (a mix of naruko and organic ericaceous food, as well as seaweed extract).
- It is kept in a spot getting a lot of sun. Until recently the weather in the UK has been quite warm and sunny, which I understand is good for healthy pines, but maybe this cooked this poor tree’s roots?
- I’m keeping it damp but not totally soaked. But maybe I really need to let pines get a bit more dry? The water where I live is slightly hard, hence the addition of ericaceous food.
I’ve added a pic showing the terminal buds still looking pretty dormant, and the needle colour. I can’t add more pictures unfortunately as I’m a new user.
Thanks so much for any advice you can give!!! 
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Couple of things to consider here:
- Buds may not be pushing if the tree is using its energy to develop roots post repot. This sometimes happens depending on the severity of the root work and the timing.
- Climate can play a part. We’ve had a unusually cool spring in the SE US this year, so some trees have been a little slower to get going. I’ve heard Peter Warren mention that JBP can be difficult in the UK due to climate. I’d imagine this is more true the farther north you go.
- Yellowing needle tips can be a sign of over-watering. Pumice is water retentive so make sure there’s balance of water/oxygen.
- Bare-rooting is not a best practice. At least you added some of the old soil back to the container. Younger trees can be more tolerant of this than a mature tree.
Good luck! Hopefully it will turn the corner and push with the heat wave that’s in the forecast there.
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You’ve really kicked it in the nuts! I’m also UK based and grow them but also know Peter’s feelings very well. You know what you did wrong with the repot but what is done is done. Stop the 2 main feeds immediately. Naruko contains a touch of chemical anyway so a definite no no at this stage. Never feed a weak tree but concentrate on giving it a healthy environment. Cold pressed seaweed is ok as it’s more of a catalyst to good soil than an actual feed. Don’t keep it damp either as it needs to get fresh oxygen through the soil, be very vigilant with the watering. You need warm roots. Worry about the hardness later if the tree survives by using proper test kits, get it to grow first. My blacks are way behind my Scots and reds in a SE English climate but yours has a marathon to run here… I wold also suggest watching Peter’s new YouTube videos which are just getting off the ground. Already some useful pine advice on there aimed at UK growers.
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Thanks so much for this super advice! I have a couple of extra Qs if that’s OK 
- I’ve taken all the fertiliser off the tree - I think this could be clogging up the air in the soil as well. As someone with black pine experience in the UK should I let the soil get essentially completely dry before watering?
- That’s interesting (and a bit frustrating!) to find out that naruko contains a chemical - I thought it was an organic feed when I bought it. I’ve used it on all my trees this growing season (for the first time), most of which are much more established and in better shape. Does it have its place or would you recommend switching to a completely organic feed?
- Lastly, I don’t have a greenhouse or anything so I might need to get creative warming the roots up. I could bring the tree inside overnight - do you think that would help or just create additional problems?
I’ve enjoyed watching Peter Warren’s lockdown videos too - I watched some of his pine pinching video but not all as it wasn’t really focusing on JBP and I didn’t have any growth to pinch anyway 
Thank you again for your help! I really appreciate it.
Thanks so much for your advice and support! I think one problem is definitely that the tree is too damp, and needs a lot more airflow round the roots. I’ve tried to scrape off the upper layer of pumice to get some more oxygen in there, and I’ll definitely be more frugal with watering. Fingers crossed this little guy will recover
There is nothing wrong with Naruko, many use it and it’s a very small percentage of chemical apparently. With this tree though you need a gentle approach concentrating on getting the soil healthy. I wouldn’t bring it indoors but leave it outside and let the sun warm it. There are so many differing thoughts on feeds but getting a good living soil is I think the key. Watering is a minefield. You need to take it to the point of dryness and then water but too dry and they turn their toes up. I soon came to realise that many said learning watering was the hardest part and they were correct. Once the roots have got going it will drink more but at present look for the soil to start drying at the top and then judge when you are happy to water again… You are on track with the oxygen. When you are ready watch the rest of that video and the Q&A ones as they explain the position of double flush pines in the UK very well.
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You know this now, but you should never bare root a pine. In fact, it’s important to disturb the roots much less than with a juniper, for example. I can’t really give you a percentage, but I usually leave around 50-60% of the root mass on when repotting, always making sure to remove rotted roots and soil that has turned to mush.
Black pines love drying out before they are watered again, but as someone else pointed out, don’t let it stay dry too long. Keeping it continually damp is not correct. It should be in a mix of one part black lava to one part akadama to one part pumice. Particle size should be 1/4" to 1/16", not heavy gravel (sorry, I apologize for not converting to metric).
When it starts reviving, I would suggest a weak, balanced liquid fertilizer such as 3-3-3. While it does need feeding once it recovers, remember that they grow in harsh, nutrient poor environments. It sounds like you’ve been feeding it too much.
Good luck with your pine!
You might even consider doing a partial light, non-aggressive repot. Remember, the three different soils I mentioned need to be mixed together, otherwise you will have a soggy part where the pumice is concentrated and won’t get a good continuous water flow through the container.
Just a suggestion.
Keep the rootball intact when doing so. You just want to get some better soil in the outer ring of the pot.
