Scots pine pot move

[Brian Van Fleet]

Not that it matters much but I have been telling you guys for years that it is better to repot both Scotts and Mugos in the summer.

Vance, I've been thinking about this. It may be wise to put a finer point on that advice; such as:

"I repot Scots and Mugos when new growth looks like this {insert photo}."

A couple failures reported here could be related to the differences in growing season. Mugos in July in MI may have elongated candles, but not fully extended needles(?), while mugos in July in TX likely have opened candles, needles hardened off and in are high transpiration mode.

If this is the case, jkd may have missed the repotting window by as much as 6-8 weeks, following the blanket advice of repotting in summer. Similarly, my repotting season starts around March 10 here, but I suspect you would have lots of dead trees if you repotted everything in Mid-March in MI.

 

[Vance Wood]

Vance, I've been thinking about this. It may be wise to put a finer point on that advice; such as:

"I repot Scots and Mugos when new growth looks like this {insert photo}."

A couple failures reported here could be related to the differences in growing season. Mugos in July in MI may have elongated candles, but not fully extended needles(?), while mugos in July in TX likely have opened candles, needles hardened off and in are high transpiration mode.

If this is the case, jkd may have missed the repotting window by as much as 6-8 weeks, following the blanket advice of repotting in summer. Similarly, my repotting season starts around March 10 here, but I suspect you would have lots of dead trees if you repotted everything in Mid-March in MI.

When I repot the needles have opened, but not necessarily fully extended. I have repotted from the last of June through to the end of August. I suspect, but have no way of knowing, that maybe the roots have been brutalized too much to the point that maybe the tree would not have survived no matter what happened or when.

Nursery trees have to be approached from the point of view that it is going to be necessary to completely replace the root system. Usually, the better the quality of the stock from the point of view of bonsai potential, the worse and more difficult the root system is going to be. The same conditions that exist in nature that restrict the growth of a tree are things that restrict the outward expansion of the root system. When this happens in the nursery with a tree that has been in a container way too long the root system will grow in on itself and wrap around the inside of the container.

When this happens the tree above ground starts to take on the appearance of an older tree. Bark starts to form, the needles reduce, the internodes shrink and often the trunk thickens. When the bonsai grower finds the tree the state of the root system may or may not be understood. Teaching that the tree can be done in the summer it should also be understood that this does not mean to tear the existing root system apart any more aggressively than you would at any other time, which is what seems to be going on from what I have been hearing.

This is totally my fault for not making sure people understood this point. I may have also indicated the use of wedge cuts too aggressively in the beginning. I should have also made it more clear that I almost always put the tree which, I have started dismantling the root system, into a screen sided container to develop fine feeder roots. I usually do not put it directly into a bonsai pot until it has had a season or two to adapt to a more shallow development. It is on the subsequent repot that I start cutting into the core of the soil mass.

 

[0soyoung]

... A couple failures reported here could be related to the differences in growing season. Mugos in July in MI may have elongated candles, but not fully extended needles(?), while mugos in July in TX likely have opened candles, needles hardened off and in are high transpiration mode.

When I repot the needles have opened, but not necessarily fully extended. I have repotted from the last of June through to the end of August. I suspect, but have no way of knowing, that maybe the roots have been brutalized too much to the point that maybe the tree would not have survived no matter what happened or when.

I've followed Vance's advice for many years now. IIRC I've have had 7 different mugos that were repotted at least twice. I killed one with its third repotting and I'm reasonably certain it was because I was overly agressive with my root work. I've also killed other species by brutalizing the roots in the spring - it is indeed just as easy to kill a tree in the spring as in the fall by brutalizing the roots.

I believe that the key signal is a cessation in elongation. Extending shoots are heavy consumers of photosynthates and water (new cells are inflated by osmosis of water to expand the walls to the full cell size). Root growth surges after the rate of shoot extension has come to a halt (because photosynthates are now available for the roots?) - hence roots can quickly recover from pruning/combing damage.