Late Summer Transplanting-Leap of Faith? Or?

[Leo in N E Illinois]

Warning, your local results may vary.

I live in the midwest, north of Chicago, less than a mile from Lake Michigan. My winters can be brutal, -25 F (-32 C) was the coldest I experienced at my home, Though the last 10 years the coldest has been -17F (roughly - 27 C ) so we get very cold compared to most. Because I live close to ''the Lake'', my spring tends to be cool, some species of trees are very slow to wake up in spring. As a result I have found spring repotting to be damgerous. I've lost many maples and JBP because even though last frost was a month earlier, often, June 1 trees are still struggling to get growing when most of May never got warmer than 65 F (18 C ) because of cold wind off the Lake. Often May temperatures average about 60 F (15 C ) for the daytime high. Spruces & Hemlock love it, JBP hates it. Our summers are not too hot, usually fewer than 10 days with highs over 90F (+32 C ). Because my summers are relatively mild I have found that summer repotting, through into very early autumn have a higher survival rate than spring repotting. People as little as 5 mile further west from Lake Michigan than my location have a normal spring, where May the highs get to the low 80's F (low 28 C) pretty regularly, most ''Chicago area'' growers may not have my problems.

So I repot many things in summer, and I do work the root systems. Now when winter comes, any tree that was repotted is wintered in an unheated well house. It is a concrete vault underneath the patio in my back yard, used to house the pump for a shallow well. It hovers between 32 F to 40 F ( 0 C to 4 C ). I don't leave trees out in our brutal weather if their roots were diturbed. I do winter zone 5, and zone 4 trees outside if they have not been repott.

So for me summer and early autumn repotting works well.

 

[Leo in N E Illinois]

Note: repotting is traumatic to the trees, and there really is no such thing as a ''gentle repot'', Even with experience, regularly, when I am trying to not break up a root ball, it partially falls apart, thus breaking new root tips.. So with this in mind, for most conifers, I do no other work, no pruning, nothing for 12 months after repotting. Give the trees tome to recover. For some trees like collected Ponderosa pines, I give them 2 or more years.

 

[Vance Wood]

Just my opinion: If a root ball is so loose and the roots have not invaded it enough that is falls apart, I would think that the tree probably does not need to be repotted. JMHO.
I think sometimes people are too quick to repot a tree just because of some arbitrary schedule. Think of the Yamadori that lives and grows in a duff pocket for a couple of hundred years and does not get repotted, how do you think that happens? Just asking. Two years is too soon for Pines, I go three at least. Pines can be deceiving. They can start to put on some growth because they want to grow but in fact they may still be weak and inflicting another root disturbance too soon can kill them.

 

[ghues]

Thanks Leo and Vance for contributing to this discussion. As we agree, climatic variances and decades of experience help us mold our own techniques. Here in the PNW (@Giga) we have a mild temperate rain forest climate and thus it provides us with our own set of standards. Our winters can be unpredictable so I now shoot for the worst case scenario.
I do not recommend my late summer transplanting to everyone and only hoped to start a conversation on what variations we share or not.
Cheers Graham

 

[Vance Wood]

Summer and early fall transplanting and repotting for me depends on the species of tree involved. Most trees do best if done in the Spring but some of my favorite trees can be damaged by this scenario.