Azalea Repotting - Peter Warren Q&A

**apologies for the formatting weirdness. this is the chat transcript where peter answered questions asked during the azalea repotting live stream. the chat is ordered backwards so questions are below the answers :grimacing:

Peter: mike, post flowering repotting is possible, see earlier in the stream, but guessing you are in a hot area,

mike: Would the opening of the first flower (there is only one so far - I think it’s an outlier) be an indication it’s too late to repot? ( large base traditional import Kaho) healthy,

Peter: always water asap with azaleas, then comeback and top dress,

Garry : Do you top dress ?,

Peter: it can be, but the satsuki roots won’t penetrate the DE particles so much,

Leonard: Can this soil be amended with diataemaceous clay?,

Peter: Marsha, depends on the situation/ structure of the roots, if there is a solid root ball and water can penetrate through it then leave the core and add kanuma around it. If not, then try and and replace all soil with the kanuma as much as is possible.,

Peter: not sure on that gary, the only other rhododeron we used for bonsai, would be planted in kanuma,

Peter: vibrating machine and hammering the pot/table would be counterproductive. potentially move the tree.,

Gary: Do all azalea/rhododendron’s like the Kanuma soil, or just the Satsukis?,

Paul: Ryan, doesn’t think using a vibrating machine to settle the soil is valuable. What is your feeling?,

Marsha: what if you are not sure what soil your transplant had prior? bonsai mix vs aka vs kanuma or potting soil. since no longer ground grown…can’t bare root. do you then not plant in kanuma? I hear if not in kanuma prior, then have to bare root or plant in bonsai mix.,

Peter: yes, he was very talented but a lot of the techniques needed aftercare that was beyond the ability of 99% of enthusiasts and professionals,

Peter: but the only issue is that wet kanuma then breaks down even more easily,

Peter: you can do that paul. I would do if it was in a really deep pot,

Paul: Would you wash the percolation layer before the next layer?,

Paul: When I started using the vice grips, my wires were much tighter,

Peter: no never,

Paul: When tightening the tie down wires, have you ever used a vice grips?,

Peter: inside or out, yes. UK, very wet winters, so I barely think of watering over the winter,
CanadianChristopher: lol! well my greenhouse is heated with a ceramic heater, it starts twice/hour so it can get pretty dry in there. but yeah: wow! twice in the winter inside a greenhouse?,

Peter: different climates, different techniques,

Peter: wow…I meant twice in the winter…november and january?,

CanadianChristopher: yes exactly for me its twice a week for the azaleas, while the rest it once a week at most,

Peter: winter I would water once or twice here, but I know in other places it has to be mor eregularly,

Peter: they are taking moisture, ,

CanadianChristopher: in the winter I mean,

CanadianChristopher: do you consider azaleas to be still growing actively in the winter? i have found that my satsuki azaleas take more water than any other variety in my 3°C greenhouse,

Peter: yes, the air is used to clean up if very dusty ,

Peter: thin rooted vaireties,

Adam: Do you tease the rootball with something as you are hitting it with compressed air?,

Peter: so not such a good idea for junipers,

Peter: care must be taken not to dry out roots though,

Peter: the best bare rooting professional uses air rather than water. success rate is way higher.,

Peter: as long as the roots are moist, its fine,

Peter: I use an air compressor to blow away dirt on conifers at home. Also with deciduous,

Peter: but that is a situation to be avoided at all costs,

Peter: although pines and spruce that get bare rooted on importation into the US will survive if given the correct aftercare ,

Peter: yes. indeed,

CanadianChristopher: I guess anything that you have ectomycorhizae like pines, larches & spruces you wanto to avoid washing at all costs,

Peter: if there were some root rot issues/really bad soil, do or die situations for conifers,

Peter: Larches no, ,

Rafi: when would you wash the roots on a conifer Peter?,

David: do you wash larches?,

Peter: with more established trees, it is just to wash off the loose dirt rather than blasting away soil,
Peter: douglas, yes, almost always. I will wash deciduous stuff as well, but very rarely any conifers,
Douglas: Do you always use the water wash when repotting azalea? Deciduous? ,

Peter: proper drainage in the first place. If you have dead roots, then the tree will probably have died or get so weak its useless before they start to rot,

Garry : What is used for root rot ?,

CanadianChristopher: True that Peter! I have lost 2 or 3 azaleas in pots that were too small :-(,

Peter: especially in hot climates,

Peter: that was mentioned at the start, first five minutes. makes for easier cultivation,

Peter: satsuki love a big pot,

Peter: Garry, yes, but is less water absorbent, therefore less suitable for water loving azalea,
David: is it me or does the pot seem a bit big,

Garry : Can lava rock be used with azalea ?,

Peter: diane, no pumice,

Peter: with azaleas, similar, but if vigorous, if there isn’t any green on it, it will still grow top and bottom,

Diane: is the dark pieces in soil mix charcoal?,

Peter: gary yes,

Peter: Beth, what is important is the consistency of it,

Gary: Thank you Peter. Just to clarify - is your last answer for the scenario where we leave the folliage and reduce the roots during the repot?,

Lynn: where do you get those sieves?,

Peter: Beth…err…big, medium and small,

Peter: Gary, sorry, didn’t read the question properly, its 3 am. it may struggle to get going, but eventually get back to heath. apologies,

Douglas: Should the roots be washed on deciduous trees when repotted? ,

Beth: What sieve sizes were you using?,

Peter: brad, its hard to be specific, but I am always a fan of leaving things to grow when trying to build up vigour,


Gary: So what made you recommend proportional reduction of the root ball/folliage earlier? ,

Peter: gary it should bounce back fairly quickly. start growing well,

Gary: Would the extra folliage help rebuild the rootball faster?,

Brad: thanks can we use Motobadome (cut leaf at the petiole to encourage new leaves/shoots) instead to encourage rejuvenation?,

Gary: What would happen to a nursery stock Azalea if we repoted/reduced the root ball a lot but didn’t trim the folliage and then had good after-care (e.g. misting, keeping out of strong wind/sun)?,

Peter: Tom, sometimes you may want to, but just to wash the dirt off rather than be agressive and remove soil,

Peter: brad, sounds familiar when standard bonsai approach is applied to azalea,

Tom: Peter did you wash the underside of the rootball with the pressure washer?,

Peter: ok. tree has to be vigorous to cut back really hard. ,

Brad: Sorry: cutting back into hard wood to invigorate new shoots… We haven’t really been trained too well on rejuvenation techniques. b,

Peter: This work here is super delicate,

Peter: kojikukiri ?,

Peter: wayne, no major experience with kurume, but they are similar. Except you never cut kurume back really hard,

Brad: Thanks Peter, we’ve been watching specimens depart now for about 7 years like this and finally we sent trees to pathology departments. I’m beginning to think we don’t kojikukiri often enough and the trees weaken enough for the fungus to find warm moist southern temps + weak tree= opportunity to run. Often once the first branch is seen weeping but leaves remain on, it’s already running the live vein several branches higher and lower. awful…B,

Peter: will make it easier to back bud,

Wayne: how applicable is all this to kurume?,

Peter: Aesthetic and health reasons,

Peter: as long as neither is so strong it will take the bark off,

Peter: david, it was a water pump. you can use standard water pressure with a jet attachment,

Attila: Is the brushing the trunk for aesthetic reasons?,

Kim: would the two color be a chimera,

David: is this standard water pressure ,

Peter: Take a cutting from the pink/white area,

Peter: Wayne. Just go straight to it.,

Peter: grow it up as much as you can, wait for the "muscles" to develop on the live vein and then take it from there,

CanadianChristopher: i have a friend who has a 3 color satsuki azalea: pink flowers, white flowers and pink&white flowers. I’d like to take some cuttings and preserve the 3 colors on the future plant. is it true that only cuttings taken from pink&white colors will work or i can take any branch on the tree?,

Wayne: how would you transition a satsuki to kanuma (or kanuma & pumice, 4:1),

Peter: Paul, I would grow the top as much as possible . There will be some live vein dieback I am sure,

Peter: Brad…nothing I have much experience of at all I am afraid. will look into it. ,

Paul: After last repot three years ago, I lost a major branch and the top. Apex is coming back but how replace lost branch. Diagnosis: isolated poor soil chop sticking. Treatment: thread graft?,

Peter: more vigorous, the tree, the higher the "sap pressure" will be and, it will burst out all over the place. kind of like a water pipe, with weak points. The higher the vigour, the more likely it is to burst through the trunks and branches,

Brad: Peter, just an fyi on fungal diseases several of us in Atlanta are struggling with Phomopsis/Botryospheria azalea canker diseases (opportunistic fungus arriving in heavy cuts like field cuts). Several imported collection pieces are now gone as it ultimately kills the tree one branch at a time. According to two pathology departments we’ve used to diagnos this, in Miss & Georgis, there is no treatment. Trying to cut it out usually kills the patient. Would enjoy a further discussion on this in the future,

Peter: Gary on both, dependent on the vigour of the tree,

Peter: but satsuki are semi-deciduous so they will have lost some leaves,

Gary: Do Azaleas back-bud on new wood or old wood?,

Peter: clean it up a little, remove some larger leaves,

Peter: Jonathan you can do some pruning, and that will be done at the end of the stream,

Jonathan: and clear the foliage? or dont touch it?,

Peter: Jonathan. no. no defoliation required unless you go super crazy on it,

Peter: Attila, was using scissors earlier, will use them later,

Peter: Gary, not really too sure of nursery stock and varieties available, ,

Jonathan: it is necessary defoliate the tree with transplant???,

Attila: Peter, not to jump forward too much, but you are only scraping the rootball, so far. Are you ever using scissors, to cut around the root ball, or scraping is all that you will be doing?,

Peter: bonsaiguy, but try and get the majority of it off so that you have consistency throughout the pot,

Gary: Thank you Peter. Do you know of others that are easily available in the US that make good bonsai? Would looking for dwarf varieties be good because of small leaves?,

Peter: there are lots of different types, Satsuki azaleas, are just one type.,

Peter: rhododendron is a massive family of plants,

Peter: bonsai guy, if the tree looks like it is strong enough, get rid of it and then really take care afterwards, if it isn’t then try and water/ care carefully and build up the strength,

Diane: I have 40-50 feet of Azalea hedge that is 4-5 ft tall in front of my Florida home. Going to try using some of the info from this vid and previous one and see what happens.,

Gary: When I look at nursery material in the US and some are labeled ‘Azalea’ and some ‘Rhodo’, what (if anything) are the major differences?,

BonsaiGuy: Do I remove all the field soil when I repot or repot like a yamadori repot, keeping some field soil working in Kanuma?,

Peter: if you can figure that one out then let me know gary. Build up the vigour and it will burst out in lots of places, then you can decide on which to keep,

Gary: If I have nursery stock and all the ramification is too high up (but I like the nebari/trunk movement), would taking out all the upper branches going to be just a crapshoot, or is it possible to guess where the new branches will come out?,

Attila: Good point, Ryan: peat moss to kanuma transition!,

Peter: the more vigorous the tree the more it willback bud. When taken from field, at their most vigorous, they are cut hard to nothing,

Peter: GAry depends on the vigour of the tree,

Peter: you don’t repot to schedule, but you can be pretty certain that the kanuma breakdown will happen on that type of time scale,

Gary: Are there any rules of thumb for how Azaleas back-bud when pruned? Especially if heavily-pruning to main branches/trunk?,

Peter: generally look on a three to four year cycle, less if it is on shallower / smaller pot,

Peter: lots of factors,

Peter: its a soil breakdown thing, slightly variety based, cultivation based, quality of kanuma ,

Peter: it may be mentioned later.,

Grayson: Or is it just a soil break down thing?,

Peter: Rafi, not really showing issues, last repotted…quite a long time ago I think,

Grayson: Yes would also like the signs of this tree needing a repot,

Peter: linda, just azaleas, but some delicate deciduous you may want to err on the side of caution,

Rafi: and when was it last repotted?,

Rafi: was this tree already showing problems of water percolation and balance H2O/O2?,

Peter: david yes,

Gary: so the leaves still being a dull red - what does that say about where the tree is at this point?,

David: would this advice apply to kusiatum azalea?,

Linda: Is the two finger depth from pot edge to root typical for most bonsai or just azalea?,

Peter: bonsaiguy so its in field soil?,

Peter: with nursery stock though it should be vigorous as hell,

Brian: What other species would/could you use Kanuma on?,

BonsaiGuy: Hi Peter…i got an Azalea last Spring thinking at the same time I was getting Kanuma. Now that I think it survived the winter, i am wanting ti repot it, now that I will be receiving Kanuma. It is in the field soil it came in.,

eter: yes,

Gary: when you say leaf/root balance, do you mean that you would try to be proportional as to how much roots/folliage you remove?,

Peter: Kanuma has big positives and negatives. As long as you understand the negatives and work around those, then you can mitigate them and use the positives,

Gary: The leaves are still dull red/brown - does that mean it’s too early to repot?,

, and live in a cave in the high sierras now :),

Peter: pruning dependent on foliage to root ratio, and vigour of tree,

Rafi: seems crazy to me to use this Kanuma soil. Turns into a mud wall,

Peter: you can bare root if the nursery stock is super strong, ,

Gary: Would you bare root? prune and repot at the same time, or repot, leave folliage and then prune when there are signs of new growth?,

Gary: How differently would you approach repotting a nursery stock Azalea from the US?,
, British Columbia). It came from Nakayama’s nursery, Japan. It was in kanuma. It died a year later. When I tried to save it, the kanuma was completely broken down. A lot of mud at the bottom of the pot. It was a very old tree, and I never got over the los, even after 15 years.

Peter: Edgardo, yes, absolutely,

Peter: you can do it at most points, depending on how harsh it is. the harsher the repot is likely to be, the sooner in the season you should do it,

Edgardo: is it ok to mist the foliage several times a day after repotting?,

david: I missed the earlier discussion. Did you mention how frequently azaleas need to be repotted?,

Gary: What are the signs that it’s too late to repot? Is it flowering, or just new green leaf growth?,
Peter: anything weaker in the shade,

Peter: otherwise full sun is ok,

Peter: depends where you are. Any where up to say 30 C / 85 F then keep in shade in the heat of the summer,

Rafi: Peter, azaleas prefer partial shade being a shrub instead of full sun?,

Peter: shallow pots are possible for some species, but watering will be much more difficult, and would be not a good idea in anywhere hot,

Peter: that was mentioned at the start of the stream. Ideally a slightly deeper pot should be used as they do better in it, the depth acts as a water reservoir / heat sink,

Grayson: @Kendall question for Peter, this seems like a very deep pot for that tree. Is there a reason for that specifically for Azaleas or can you use much shallower ones? Does this affect repotting frequency?,

eter: Mike, no I have never seen it. what would be best and this will come up is to use a larger hole sized drainage mesh,

mike: No - just picture a small inverted cone of mesh over the drainage hole inside the pot. No big deal if it’s never done. Misinformation I’ve picked up along the way most likely. ,

Peter: mike, is that external to the pot? Seems a bit convoluted.,

mike: Yeah - like an inverted cone of mesh over the drainage holes - or something larger - so the surface which is facing air is larger.

Peter: Wayne yes, with any metal tool you have to be careful not to damage the pot,

Mel: @Rafi it’s fine kanuma,

Rafi: is that osmocote mixed in with the substrate?,

Wayne: Is there any concern for the pot with the root saw?,

Peter: inverted mesh cages?,

mike: I’ve heard that in an effort to improve air in the roots, inverted mesh cages are sometimes used to increase the air space under the tree - is this done in current practice anywhere?,

Peter: 100% pure Kanuma is also not an issue, but I have found it helpful to put a bit in,

Peter: so that the subsequent repotting is easier,

Peter: akadama could break down and the idea is to try and keep something intact,

Peter: I will keep it on top of other bags, pumice and lava on the bottom, akadama and kanuma on top,

Rafi: why not Akadama instead of Pumice for the 20%?,

Peter: it doesn’t store well ,

Peter: most commercial nurseries will do the same. Also a tonne of peat moss is probably the same price as a bag of kanuma,

Isaac: do you recommend stockpiling kanuma if i can find it for a good price or does it not store well?,

Peter: our bonsai are designed for long term cultivation in a confined environment with different drainage and heat characteristics ,

Peter: their plants are designed to go in landscapes,

Peter: then their objectives are slightly different to ours, and so using peat moss is good for their objectives,

Attila: No, just nursery pots. Second generation azalea guy, Tom Nuccio. Tremendous knowledge of azaleas, but not in bonsai culture. His dad brought the original satsukis from Japan.,

Peter: is it a bonsai azalea nursery?,

Peter: yes, but ideally try and get something that is particle sized rather than mud,

eter: edgardo, pure pumice would be very difficult to grow into. Akadama is also possible. I would go for something organic if no kanuma or Akadama ,

Edgardo: Hi Peter, Can we use Pomice if we can´t get Kanuma Soil? Thank You,

Peter: no dave, remove the flowers once they start to fade, a bit earlier,

Peter: Yes Jeff,

david: If you repot before shoot growth, do you remove the flower buds that year?,

Minnesota Jeff: Would removal from a nursery container be somewhat equal to removal from the field?,

This is very cool. If you tag someone during the chat and your username is the same in the live stream and the forum then the mention works…