Summer repottimg. You know it is listed in many books as the ''second season'' for repotting, usually noting that for what ever reason it is not as good as early spring, but it is not an ''unheard of'' time for repotting.
I have too many trees, and not enough time. As a result I loose several every year for one bone head reason or another. Sometimes I can identify the cause, sometimes not.
My ''Mugo Train'' ticket tree is my 3rd mugo. My 2 earlier mugos perished, long before I ever saw or rather seriously read Vance's posts on mugo. I no longer recall the why for them, most likely too many things done without allowing enought time to pass. For my new mugo, it was a tree picked up from a bonsai club member, and I am taking my time with it. Apparently it was repotted last year, and had all the year's new growth removed sometime in that same summer. So this year it has new buds all over. I'm going to let it grow. I won't repot for several years as it is in a suiable training pot, and the mix is very similar to my own, draining well. I will re-read Vance's directions, but likely I won't de-candle until summer 2017, and won't restyle it until it is bushy, and I have lots of branches to choose from.
But Vance's ideas on summer repotting do echo my experience with cork bark JBP. I have been dabbling with bonsai and cork bark JBP for 35 to 40 years. Over this time I have owned over 30 different cork bark JBP. The longest I kept one going was 18 years, got over excited with how great its bark was becoming and did too much to it in one year, repotting, styling, and candle pruning all in rapid succession.RIP. I line north of Chicago, south of Milwaukee, in a climate that is too cold for normal JBP to be reliably hardy. Cork barked JBP seem to be much less vigorous, less cold tolerant, and much less reliable than regular JBP. The mutation really does leave the tree with issues that make it much more succeptible to ''sudden death syndrom''.
I live close to Lake Michigan and often have long, cold springs, where temps never get above 60 F for any length of time until after first of June. Cork bark JBP need heat to wake up and grow. The 7 corkers I have, that are still alive, are just pushing new growth now, the last week of May.
I found over the years that I can loose a pine after a spring repot, and after a summer repot, but for my cork bark JBP, in my climate, a summer repot seems to have a greater degree of success. I definitely have fewer issues if I hold off and don't repot until late June, or early July. It is important to note that I on the average I have fewer than 10 days a year above 90 F. So trees can grow all summer long without serious heat stress. In autumn I do bring newly repotted trees in before temps drop below 28 F after repotting, as I fear the new root system may be more touchy about cold that an already normally touchy cork bark JBP would be. I had started over (again) with cork barks, and my oldest is only about 5 years in my care, but since moving to summer repots, I have stopped loosing so many right after repotting. I have one that is old enough to have fully developed cork on the trunk, but not the branches. The other 6 are young, grafted trees, all picked up within the last 5 years. Maybe before I'm crippled and crazy I will have a ''corker'' with actual cork, and enough green needles that I would not be embarrassed to show it.
Key is, technique and timing should be adjusted to how a tree responds in your own climate. Living north of ideal JBP climate, I have found summer repotting is on the average ''less risky'' than early spring repotting. If you live in Atlanta area, or other more ideal JBP territory, or an area with brutally hot summers, you might not get the results I'm seeing. But my cool springs, with trees that ''wake up'' late, summer repotting works for me.
Slippoted to the ground.
