Repotting Aftercare

[zeejet]

I’ve received some conflicting information about repotting and wanted to get some clarity as I’ve kind of put myself in a corner with a recent coast redwood repot:

• Recently repotted a coast redwood prebonsai during conifer repot season (late spring)
• It’s almost an inch in trunk caliper but came in only a 1-gallon nursery pot and was rootbound with thick roots encircling.
• I remembered the guideline regarding removal of no more than ⅓ of the root mass incorrectly and thought I should remove until ⅓ was remaining. I ended up removing slightly more than half the roots.

The aggressive root-prune has got me wondering about best practices around aftercare.

For repot/root-pruning aftercare, the conventional wisdom is to stick in shade and don't do anything else to the tree. However, I’ve attended two workshops this year with a prominent local bonsai practitioner where he had us prune and partially defoliate in order to reduce the amount of foliage that needed to be supported by the roots. Both the trees I worked on with this strategy did great (one conifer and one deciduous).

At this juncture, I’m not sure if I should defoliate some of the fronds and new tips or if I’m screwed either way. Should I keep this in shade if temperatures are only around 70F and partly cloudy? Any other aftercare strategies to improve my chances?

Any feedback would be appreciated!

 

[dbonsaiw]

Please share some pics of the tree. I've never worked with coast redwood but dawn redwoods (albeit different) would be fine. Of course, you may not want to leave a 10 foot tree on a substantially reduced root mass, but as they say in bonsai "it depends".

Here's some pics of serious root work I did on a JM this spring. I ended up cutting back the branches at the same-ish time as I cut off well over 50% of the roots (probably more like 90%). And JMs can be a bit pooky. Granted, I'm in 7b but it's in basically full sun and seems to be doing fine (and I also drilled holes in the trunk for 2 thread grafts). Not sure I would recommend this to others, but my way of trying to give comfort that your tree should probably be fine.

 

[zeejet]

You'll have to excuse the amateur guy-wiring, but here's the tree currently. The top is only about another 6 inches from where the photo cuts off.

 

[dbonsaiw]

Looks good to me. Let's see if folks with more coast redwood experience chime in. But I think 50% root reduction should be fine.

 

[Shibui]

I'm another with no direct coast redwood experience but, in general, I work on 50% root reduction being 'light', up to 75% is 'moderate' and, 'aggressive' root reduction is around 80%-90% reduction.
Almost all species can cope with light root work. Most can cope with moderate. Some tough species have no problem with aggressive root reduction - trident maple, olive, ginkgo, zelkova, many elms, Banksia, many ficus sp. Tolerance to root reduction does seem to change with age as well as species. Seedlings can easily recover from 90% root reduction but need to be more conservative with much older trees.
With respect to your prominent local practitioner, foliage reduction is something that was taught many years ago and some of us have never questioned or tested to see if it is the only or best method. I still find it hard to disregard the early lessons I was taught, even though I know some are not based on fact. Reducing foliage post root reduction does seem to work in most cases but we have discovered that there are viable alternatives.
I find that most trees can self regulate so there's no need to reduce foliage. Most trees will shed any excess foliage if required and maintain enough to stay alive.
In most cases I don't even bother to keep trees in the shade after root reduction. Usually root pruning happens early when the sun is not strong or too hot so not necessary. Deciduous have no leaves when repotted so don't need shade. By the time the leaves open, the tree has already adjusted to the new level of roots v leaf so shade seems redundant for deciduous. I repot a number of native Aussie species (all evergreens) through our hot summer and even they seem to manage going directly back to the full sun, even though temps can be close to 40C.

Also be aware that leaves that open in shade will be adapted to shade and can burn when the trees is moved back to full sun.
There is some evidence that shade and reduced foliage reduces the tree's ability to produce food which, in turn, inhibits new root growth. Reducing foliage and keeping recently repotted trees in shade does not usually kill them but may slow recovery.

 

[Dabbler]

Looks like you can remove the wire going up the trunk as it's not doing anything - but I think your fine

 

[zeejet]

Looks like you can remove the wire going up the trunk as it's not doing anything - but I think your fine

Yea, I've been meaning to remove it - I initially thought I would add some subtle movement with this, but that would require more dramatic bending with thicker wire I do not have.

 

[zeejet]

I'm another with no direct coast redwood experience but, in general, I work on 50% root reduction being 'light', up to 75% is 'moderate' and, 'aggressive' root reduction is around 80%-90% reduction.
Almost all species can cope with light root work. Most can cope with moderate. Some tough species have no problem with aggressive root reduction - trident maple, olive, ginkgo, zelkova, many elms, Banksia, many ficus sp. Tolerance to root reduction does seem to change with age as well as species. Seedlings can easily recover from 90% root reduction but need to be more conservative with much older trees.

Thanks for the insight - this is helpful in setting expectations and guiding future root work for me!

With respect to your prominent local practitioner, foliage reduction is something that was taught many years ago and some of us have never questioned or tested to see if it is the only or best method. I still find it hard to disregard the early lessons I was taught, even though I know some are not based on fact. Reducing foliage post root reduction does seem to work in most cases but we have discovered that there are viable alternatives.
I find that most trees can self regulate so there's no need to reduce foliage. Most trees will shed any excess foliage if required and maintain enough to stay alive.

I did not know about the history of this piece of advice. I will say though that a lot of foliage reduction came in the form of pushing back new growth to promote back budding and some initial styling as these were part of species-specific workshops where we took prebonsai material and worked them from stock. Reduction of foliage from direct removal from the petioles was not what were were aiming for.

In most cases I don't even bother to keep trees in the shade after root reduction. Usually root pruning happens early when the sun is not strong or too hot so not necessary. Deciduous have no leaves when repotted so don't need shade. By the time the leaves open, the tree has already adjusted to the new level of roots v leaf so shade seems redundant for deciduous. I repot a number of native Aussie species (all evergreens) through our hot summer and even they seem to manage going directly back to the full sun, even though temps can be close to 40C.

This was my intuition as well - the shade advice seems to center around water resource management when temperatures are hot and the added stress from cooling needs become a factor.

 

[dbonsaiw]

Ended up looking into coast redwoods a bit and they (as well as sequoia) seem to be sufficiently different from dawn redwoods to warrant different treatment (or at least more research). DRs are "deciduous conifers" and I basically treat them the same as bald cypress - which is to say like a Sherman tank. Coast redwoods and sequoias appear to be true conifers. Maybe a more conifer-friendly approach is needed for this species. Nothing to do at this point other than care for the tree and report back so we can learn too.

 

[zeejet]

Ended up looking into coast redwoods a bit and they (as well as sequoia) seem to be sufficiently different from dawn redwoods to warrant different treatment (or at least more research). DRs are "deciduous conifers" and I basically treat them the same as bald cypress - which is to say like a Sherman tank. Coast redwoods and sequoias appear to be true conifers. Maybe a more conifer-friendly approach is needed for this species. Nothing to do at this point other than care for the tree and report back so we can learn too.

That's my impression as well - although they do prefer cool climates with high humidity and lean toward water in the water-oxygen balance. The tricky part for me is the humidity and moisture while also maintaining full-sun to part shade.

I'm currently splitting the difference and keeping it under shade cloth and giving it some sun, but not full. I have a SW facing covered balcony which means only afternoon sun so 40% shade is being applied.

 

[n8]

I've gone very hard on root reduction of coastal redwoods (aggressive by Shibui's percentages). They can handle a lot.

I wouldn't worry about shade. I leave mine out in full sun for most of the summer and we're much hotter in the Sacramento Valley than SD.

I would not defoliate. (When you are ready to develop foliage pads for your redwood, look up how to pinch tips. This is also where full sun will help with tight pads.)

My only concern is the pond basket as they prefer to stay moist. Probably OK in your location, but I'd water often as it will dry quick on warm or windy days.

 

[zeejet]

My only concern is the pond basket as they prefer to stay moist. Probably OK in your location, but I'd water often as it will dry quick on warm or windy days.

Noted - I don't currently have extra grow boxes (need to build some) and I have extra 10x10x6" pond baskets. I did wrap the outside in plastic wrap though so it's effectively just a 2-gallon square container with a lot of bottom drainage at this point.