Query about the timing and biology of fall repotting

[Lars Grimm]

Hi All,

I understand the timing and biology of spring repotting for deciduous trees. You wait until the buds start to extend which is usually an indication that the trees resources have transitioned out of the roots and into the tree itself. This allows safe root pruning without depleting resources and the cool Spring weather encourages new root growth.

Several species of deciduous are often recommended for fall repotting, such as japanese quince. I am confused about how best to time this. I would assume immediately after leaf drop would be best. But from a biology standpoint, why does it make sense to repot a tree in fall when the root growth would be less vigorous or would have a more firm end date during deep Winter. Additionally, the new roots would be more likely to freeze over the winter. I understand that root growth is encouraged with cooler weather but not typically during the harder cold of winter.

Thanks,
Lars

 

[just.wing.it]

Interesting....
Where did you see I do about recommended fall repotting?

 

[rockm]

http://www.mortonarb.org/trees-plan...ticulture-care/fall-planting-trees-and-shrubs

 

[Paradox]

http://www.mortonarb.org/trees-plan...ticulture-care/fall-planting-trees-and-shrubs

I read the article, and it seems more geared toward trees planted into the ground where they would be below the frost line and/or covered in an insulating layer of snow. Yes that works and trees live with no issues.

I do question how well this would work with potted plants that might then be subjected to frozen pot/soil. I would be concerned that any new root growth would be killed. If protected from freezing, they should (?) be fine.

 

[Lars Grimm]

[QUOTE="just.wing.it, post: 486313, member: 19277"]Interesting....
Where did you see I do about recommended fall repotting?[/QUOTE]

Bonsai4Me
International Bonsai

 

[0soyoung]

I understand the and biology of spring repotting for deciduous trees. You wait until the buds start to extend which is usually an indication that the trees resources have transitioned out of the roots and into the tree itself. This allows safe root pruning without depleting resources and the cool Spring weather encourages new root growth.

This is not at all what trees really do. They aren't potatoes. Energy is stored though out the tree as starch grains in living cells, but no matter. It all starts with temperatures above roughly 40F after the chilling requirements (hours below roughly 40F) have been satisfied.

Several species of deciduous are often recommended for fall repotting, such as japanese quince. I am confused about how best to time this. I would assume immediately after leaf drop would be best. But from a biology standpoint, why does it make sense to repot a tree in fall when the root growth would be less vigorous or would have a more firm end date during deep Winter. Additionally, the new roots would be more likely to freeze over the winter. I understand that root growth is encouraged with cooler weather but not typically during the harder cold of winter.

Once 'awake' and actively growing, temperate species change the way they grow by detecting the summer solstice. Prior to this, most of the products of photosynthesis are devoted to creating more above ground tissues, so little actually gets to the roots. Following, all that new hardened foliage is available to drive root growth, finish building new tissues, and to be put into storage. So about a month after the summer solstice is a good time to dig/repot conifers and waxy leafed angiosperms like chaenomeles, azaleas, elms, and oaks, to name a few. Even delicate Japanese maples can be repotted whenever new growth is not extending (e.g., May-ish, July-ish). The issue, though, is that moisture is also lost through leaf surfaces, so 'after care' can be very important.

I prefer to repot/dig quince and azaleas after the summer solstice because it is so easy to knock off the flower buds in early spring. Trying to wait until after flowering doesn't work out well because they are extending new growth before the flowers have completely faded.

After leaf fall can be a good time to plant nursery stock with which one just loosens the roots from the outside of the 'root ball'. Similarly, one can 'slip pot' a deciduous tree after leaf fall, but I don't think it a good idea to bare root and/or root prune a leafless tree. And now we're into the whole thing of how can roots grow and be hardened for winter cold as opposed to roots grow and aren't hardened because of late fall and/or early winter root pruning. I imagine this has to do with available sugars (sugars are food and antifreeze) versus the competing process to convert sugars to starch grains for over winter storage. Blah, blah, blah.

 

[M. Frary]

They aren't potatoes

No truer words have been spoken here.

 

[MrFancyPlants]

Brent Wallston has a great article on it: https://www.evergreengardenworks.com/fallpot.htm


I am going to reread https://www.evergreengardenworks.com/growprin.htm to see if I can glean any other nuggets.

 

[Stan Kengai]

I just repotted Japanese quince this evening. In my climate, they go through a semi-dormant period from mid-July to the end of August. Temperatures are starting to drop, and rain is forecast for the next 3 days. The quince will begin another short growing period that lasts through mid-October. I'll also repot apples, Chinese quince, roses in the next week or two. Our average first frost is mid-November, so there is plenty of time for roots to grow and harden.

I couldn't tell you the exact science behind it, but I know it works. I would guess it is akin to a minor spring after the semi-dormant summer period.

 

[twisted trees]

At the International Bonsai Arboretum we've been reporting almost all season. It depends on the health of the tree and how vigorous a treatment and aftercare.

 

[0soyoung]

To note the words of @jkl, who passed on a little while ago and was a friend of Bret Walston's,

you can repot most any time, if you know what you are doing

Or words to that effect, were a favorite reply of his to repot timing questions.

 

[Soldano666]

Ive been digging and bare rooting larch for the past week. That articles says larch isnt good for fall planting. Nick lenzs book says they are.... l dont know what to believe anymore. Proof is in what you can do

 

[0soyoung]

Proof is in what you can do

As long as you can do it more than just once.
Science, I love it.

 

[Lars Grimm]

I just repotted Japanese quince this evening. In my climate, they go through a semi-dormant period from mid-July to the end of August. Temperatures are starting to drop, and rain is forecast for the next 3 days. The quince will begin another short growing period that lasts through mid-October. I'll also repot apples, Chinese quince, roses in the next week or two. Our average first frost is mid-November, so there is plenty of time for roots to grow and harden.

I couldn't tell you the exact science behind it, but I know it works. I would guess it is akin to a minor spring after the semi-dormant summer period.

Your climate is probably not that different from mine in NC. We have still had 85 degree days though with some short stretches in the 70s. What type of aftercare do you provide your bare rooted plants then besides shade?

 

[rockm]

I read the article, and it seems more geared toward trees planted into the ground where they would be below the frost line and/or covered in an insulating layer of snow. Yes that works and trees live with no issues.

I do question how well this would work with potted plants that might then be subjected to frozen pot/soil. I would be concerned that any new root growth would be killed. If protected from freezing, they should (?) be fine.

Well, yeah, new growth will be killed if the tree is repotted too late and isn't insulated from deep cold. That's a risk with fall repotting.

 

[my nellie]

... ...but I don't think it a good idea to bare root and/or root prune a leafless tree... ...

In accordance with this, how would you treat a nursery deciduous tree if you were to root prune for the very first time and repot it into a shallower pot ?

 

[Waltron]

one thing that I have just recently noticed, the tree's friend the mushroom is fruiting right about now. some mushrooms fruit in spring, some in fall. (white, michigan) spruce, jack pine and larch's mushroom friends are actively growing, and fruiting right now. id call this late summer rather than fall. the sphag moss and mushrooms grow together with the tree roots. the tree's roots, the moss, and mushrooms are all very active right now. Therefore I think that late summer, early fall is a great time to collect, or repot certain species. of course every situation needs unique considerations, health etc, all depends on how aggressive work you plan to do and what you are trying to accomplish. But also it has started to rain a lot more now, and there is plenty of time before we get an actual worrisome freese in my opinion. I've collected several larch in August.

 

[Stan Kengai]

Your climate is probably not that different from mine in NC. We have still had 85 degree days though with some short stretches in the 70s. What type of aftercare do you provide your bare rooted plants then besides shade?

I don't give them any special treatment, not even shade. They go right back on the bench.

 

[BeebsBonsai]

I don't have much to share, as this is such a highly debated topic, but I will say one thing. I don't believe it would ever be a good idea to damage the roots of a tree when it didn't have leaves to help generate the carbs that repair the damage.

 

[Waltron]

beeb's.. how long you been doin bonsai?