repotting late summer/early fall?

benw3790

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Haven't been on here in a while, have been moving and have had a lot going on lately! I feel fairly confident, my knowledge for bonsai has grown a lot, since that last time i posted, as i havebeen spending more time with my trees. Letting them teach me and learn from them all summer vs asking questions on the forum. As it gets closer to autumn I see and hear about people repotting trees, now that the worst of summer is over. I've read that there could be a short window in between summer and fall to repot certain species of trees. Species I have in mind are junipers and crepe myrtles. I've always heard to only repot junipers while they are dormant. And I akways ususlly only repot my deciduous trees in early spring, right before bud break but these CMs are really really root.bound. does anybody have any experience with autumn repotting or any comments on this in general? Thanks!
 

jk_lewis

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I've been repotting all summer, but then, until the last 3-4 days it has been a really, really cool summer.
 

Vin

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I'm not sure you'll be accomplishing much by repotting your CM's at this point. Your temperatures will be falling soon and they will go into dormancy naturally. If they have made it through the summer then a few weeks isn't going to hurt them. Why rush it especially if you are going to be doing any heavy pruning or root work; which you will most likely need to do if they are rootbound. Just my opinion though.
 

Eric Group

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Haven't been on here in a while, have been moving and have had a lot going on lately! I feel fairly confident, my knowledge for bonsai has grown a lot, since that last time i posted, as i havebeen spending more time with my trees. Letting them teach me and learn from them all summer vs asking questions on the forum. As it gets closer to autumn I see and hear about people repotting trees, now that the worst of summer is over. I've read that there could be a short window in between summer and fall to repot certain species of trees. Species I have in mind are junipers and crepe myrtles. I've always heard to only repot junipers while they are dormant. And I akways ususlly only repot my deciduous trees in early spring, right before bud break but these CMs are really really root.bound. does anybody have any experience with autumn repotting or any comments on this in general? Thanks!
The answer to your question will vary based off what kind of winters you have. Where in NC do you live?

Here in sunny south Cackalacky I have had some great success repotting deciduous trees in early Fall/ late summer. Depending on how early in the season you do it, you might consider at least a partial defoliation to lessen the strain on the roots after they get worked... I did a late summer repot on a JM I have last year (inspired by a FB post from Walter Paul where he repotted a huge JM Bonsai he has) The concern is that a early freeze might damage newly developing roots. We had one of our coldest winters ever here last year and the Map,e was SUPER happy this Spring!!
CM is a little more cold sensitivity an maples in my experience, so I would encourage you to provide protection over winter during the coldest nights- whether you re pot it in Fall or not.

The benefits are many- you are usually stimulating an end of season growth spurt for your tree (both the roots and the branches) by pruning and getting it into a new pot with more room... My Maple last year shot out a 2 foot shoot between late September and when it started to go dormant (just a couple months). This is good for developing trees obviously not a great asset for more developed/ established trees, but the increased ramification tends to naturally limit the growth... The real benefit for me- again, dealing with trees Iw ant to fatten up and continue to develop- is that you start the next growing season with a tree that has already established itself in the pot! No chopping roots and eliminating all that stored energy from dormancy, no waiting for the tree to bounce back through half the Spring when it should be growing... As soon as the leaves are ready to pop, the tree is going full speed! It is like gaining an extra growing season almost.

The timing is important, but it is best to error on the side of doing it early if you have harsh winters to contend with. WE all think trees are best repotted in the Spring, but the trees don't know that... They respond to good care, and it doesn't really matter when you do it, it is the after care and soil medium you use that is more important than timing. You can repot in mid-winter if you protect the tree, or mid- summer if you give it some shade until it starts growing... The idea that it is best to repot in the early a Spring is- I think- primarily meant to mean that is the easiest time for most people to do it because the temps are moderate, the trees are about to start growing again which quickly reassures us we repotted at the right time... In other words it is a blanket recommendation meant to make it easy especially for beginners. It is not a hard rule based off of biological necessity.
 

Eric Group

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I'm not sure you'll be accomplishing much by repotting your CM's at this point. Your temperatures will be falling soon and they will go into dormancy naturally. If they have made it through the summer then a few weeks isn't going to hurt them. Why rush it especially if you are going to be doing any heavy pruning or root work; which you will most likely need to do if they are rootbound. Just my opinion though.
The roots do grow all through the Fall and even some during the winter (again, depending how cold it gets). I think a tree repotted in September is going to handle a winter better than one that is terribly root bound... But I don't know for sure, we generally have pretty mild winters around here... Not quite as mild as your locale obviously...
 
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is repotting pines sketchy in the early fall? Or could I slip pot my seedlings in the ground?
Thanks.
Porter
 

Vin

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The roots do grow all through the Fall and even some during the winter (again, depending how cold it gets). I think a tree repotted in September is going to handle a winter better than one that is terribly root bound... But I don't know for sure, we generally have pretty mild winters around here... Not quite as mild as your locale obviously...
What would concern me with CM's is how the tree would react to root pruning when most of the energy is focused toward root growth and storing energy. I hard pruned a few of mine late in the spring as the buds were breaking and I thought the they were going to bleed out. For about a week you could actually see the sap oozing from the wounds. You're way more experienced at this than I am so I may try repotting one in November and see how it compares to one I'll repot in March(ish). They have some fairly decent bases so I'd hate to lose one.
 

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Stan Kengai

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The general guidelines I follow, both from teachers and practical experience, is as follows:

Repot conifers in the spring because fall repotting benefit is null.

Early fall repotting, as temperatures begin to cool, of deciduous trees with moderate root pruning is acceptable, and can sometimes be advantageous, so long as you can protect them from significant freezing during the winter. I keep mine in a cool dark garage where temperature fluctuations (this is the biggest concern in the Deep South) are moderated.

Heavy root pruning should wait until late winter/early fall.
 
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benw3790

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The answer to your question will vary based off what kind of winters you have. Where in NC do you live?

Here in sunny south Cackalacky I have had some great success repotting deciduous trees in early Fall/ late summer. Depending on how early in the season you do it, you might consider at least a partial defoliation to lessen the strain on the roots after they get worked... I did a late summer repot on a JM I have last year (inspired by a FB post from Walter Paul where he repotted a huge JM Bonsai he has) The concern is that a early freeze might damage newly developing roots. We had one of our coldest winters ever here last year and the Map,e was SUPER happy this Spring!!
CM is a little more cold sensitivity an maples in my experience, so I would encourage you to provide protection over winter during the coldest nights- whether you re pot it in Fall or not.

The benefits are many- you are usually stimulating an end of season growth spurt for your tree (both the roots and the branches) by pruning and getting it into a new pot with more room... My Maple last year shot out a 2 foot shoot between late September and when it started to go dormant (just a couple months). This is good for developing trees obviously not a great asset for more developed/ established trees, but the increased ramification tends to naturally limit the growth... The real benefit for me- again, dealing with trees Iw ant to fatten up and continue to develop- is that you start the next growing season with a tree that has already established itself in the pot! No chopping roots and eliminating all that stored energy from dormancy, no waiting for the tree to bounce back through half the Spring when it should be growing... As soon as the leaves are ready to pop, the tree is going full speed! It is like gaining an extra growing season almost.

The timing is important, but it is best to error on the side of doing it early if you have harsh winters to contend with. WE all think trees are best repotted in the Spring, but the trees don't know that... They respond to good care, and it doesn't really matter when you do it, it is the after care and soil medium you use that is more important than timing. You can repot in mid-winter if you protect the tree, or mid- summer if you give it some shade until it starts growing... The idea that it is best to repot in the early a Spring is- I think- primarily meant to mean that is the easiest time for most people to do it because the temps are moderate, the trees are about to start growing again which quickly reassures us we repotted at the right time... In other words it is a blanket recommendation meant to make it easy especially for beginners. It is not a hard rule based off of biological necessity.

Yeah my only concern was that, if I did root work this late in.the season it might take away the energy that they will need to get through winter. Our winter this past year wasn't too bad and I have an unheated garage for over wintering. The CMs in question are so rootbound, that there is hardly even.any soil in the nursery containers that they are still in. Its ALL roots and they are matting up underneath the pot through the drain.holes. so you don't think doing root work to them now wouldnt take the energy they need store for.winter? Im not worried about being able to protext them from cold temps just was worried about making them weak right beforewinter. We still have 3 months to go tho! And the junipers in question are.extremely rootbound too. There are wayy too many roots vs foliage. Also I might add that these CMs are very ypung, still in nursery containers and have fairly small trunks. I bought them like they sit. Just chopped the trunks back to shape and am working with all new shoots/branches from this growing season. Most of the shoots haven't even hardened off yet completely. And I am in south western NC 45 minutes north of charlotte.
 
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Based on Brent Walston's 'principles of growth', I often repotted in the early fall and would suggests slip potting the pines into the ground in order to over winter them. My standard over wintering process is to dig out some trenches in the garden.. Put down a gritty drainage layer and then your pots, deep until nearly the rim and refill with a mix of mulch and/or black cow, and something cheap and granular. You would have to be carefull with the roots but might risk spreading the roots over rocks or tiles.
Brent later ammended his fall repotting article to warn for extra cold protection, but I have found no need to keep it warmer than the ambient soil temperature in my climate. Some yamadori collectors will bury pipe heating cables (so they don't burst) into their beds for extra protection from the low end temperatures if that is a concern. Many club members in my area lost trees this winter attributing the losses to the cold, but were keeping them in their garage, which just sounds tricky to keep the humidity and temperature correct, while the trees have been doing it for quite a while in the ground on their own. Assuming your stock is hardy to your area... I do keep tropicals in my basement here, and they are a lot of fun despite their challenges.

David
 
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And to the original responder, CM should be fine to repot now for both our areas, but it is slightly dependent on which variety of CM since Lagerstroemia indica does rapidly hybridize with more tropical varieties. Mine has been slower to come out of dormancy after late season root work, winterized as described above, but it was in a shady spot back then and bounced back quick. I like the idea of repotting prior to leave fall so that I can pretend the leaf juices are withdrawn from the leaves and push back down in the form of fine feeder roots.
I would read Vance Wood's recommendations for repotting mugos from the nursery.. It would also apply to a super root bound crape. Depending on what it looks like, there may just be a layer of spiral roots on the bottom, which should be removed. Or if the whole pot is really full, take the bottom 10% off the bottom and score the sides in a few places to discourage spiraling. Maybe work some holes in if the soil is really compacted.
 

Vin

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And to the original responder, CM should be fine to repot now for both our areas, but it is slightly dependent on which variety of CM since Lagerstroemia indica does rapidly hybridize with more tropical varieties.
I must have misunderstood what the OP was trying to accomplish with his CM. Slip potting into the ground and/or removing 10% of the root ball is something I wouldn't have a problem doing if I was going to repot in the fall. I'm still going to wait until spring to work on mine as I plan to do major root work and heavy pruning. The one I posted a photo of was pruned to a stump in April I believe. I also removed about 60% of the root ball. If I didn't keep pruning it through the summer it would probably have branches no less than six feet. I'm just learning here to though. Thanks for the info.
 
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oops, I didn't mean to, i just wanted a quick answer so they could get back to their convo.
Thank you though.
 

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