Repotting Pines in Summer


In a blog post from July 10 on Jonas repotted a JBP and did minor root work in summer. In a reply to a comment he stated repotting at decandlig time was an option. So I have two questions:

  1. for young pines (2-3 year JBP in my case) is repotting in summer ok? The pines I’m thinking of are healthy but not in the best container nor are they in a ideal soil. I’d like to transition them to some better soil in a bigger container but would not be barerooting. I’m thinking of doing this now but I won’t be removing any foliage. I did the same thing to some plants from the same batch last fall and they did fine although their growth this spring seemed to lag a bit behind those that were not repotted.

  2. if repotting now will work for JBP, what time of year is better for repotting in general? Why would spring be better than decandling time for repotting or vice versa?

Curious to hear Jonas and everyone’s thoughts. Thanks.

(Jonas Dupuich) #2

One way to think about it is that repotting always slows a tree down to some extent. Depending on when we repot, we can slow down the tree a lot or a little.

In early spring, many trees begin to send out new roots. If we repot as this process begins, the new roots will emerge in new soil. If we wait until many new roots have grown, we’re asking the tree to produce new roots again which can be stressful. And if it’s warm out and the tree is active, we’re reducing the tree’s ability to take up water that it uses to cool itself down and move nutrition around.

Depending on your climate, I’d expect 2-3 year-old pines to respond well to repotting as long as the root work isn’t extensive. I’ll be repotting a few trees around this age in the coming weeks because the soil is a solid block that it hard to water, but I won’t be cutting many roots as I don’t want the trees to slow down much. If it were really hot where I live, regularly over 95, I’d proceed with caution as I don’t know how the trees would respond.

Sometimes I want trees to slow down, especially when making the transition from trunk growth to branch refinement. Repotting out of season may be useful at this stage, but I have yet to experiment a lot with the approach and tend to repot at the normal time, November through February where I live, and just cut a few more roots than I might otherwise cut.

Will be curious to hear others’ experience and to see how your trees do after this repotting!


In case anyone is interested here are some pictures of the repotting of one of the pines I was mentioning. I bought these last year. The soil is predominantly Turface which is how they came to me. I was as gentle as I could be with the rootball but a lot of the soil just fell away. I didn’t see any visual indication of the presence of mychorrhiza. Hopefully my horticultural practices aren’t responsible for that. I plan to put some more wire on it in the fall. Otherwise it will just get acclimated to it’s new home which is a terracotta bulb pan with Jonas’ ready mix for the soil. I’ll probably top it with some shredded sphagnum to help with moisture retention after it spends a couple weeks in the shade:

(Frank Corrigan) #4

I do not generally choose to repot during the growing season. My reasoning includes the increased risk as well as the interference with the growth pattern. For my trees in the nursery and on the benches the growing season is crucial to development and refinement. I have very few trees that are strictly speaking just in show maintenance mode.
That said, my experience is that young tree’s are much more forgiving and resilient. Also, i believe that as ones training and experience moves along adjusting technique and aftercare make a lot of things possible that are not generally advisable or the very best timing.
In this case you are improving the tree’s conditions and setting it up for the future. However if you do just a partial switch out then the process will have to be repeated sooner rather than later. So it depends on how much you do versus how much is required. And that leads to the question, really when is the best time for the stage and objectives for the tree?
My approach is generally to make the repot one of the first things i do when the time is appropriate. That leaves me longer periods of time to work on development or refinement between successive repotting.

(Jonas Dupuich) #5

Thanks for sharing the photos. It looks like the tree was growing well in its current mix. When young trees are growing well, I tend to leave them alone. Trees growing in the “wrong” soil isn’t necessarily a problem, especially in the short term.

The root work was also a little more than expected. As long as the tree continues to do well this year, you’ll get a better idea about the effect of this repotting had next spring and summer. With pines, the size and number of new buds and needles are the best signs as to tree health.


Thank you for the comments and feedback. So are you saying that in your opinion I might have been better served by waiting until spring and getting more aggressive with removing the soil and transitioning to the soil that I want long term?


Hi Jonas,
Thanks for your thoughts, feedback, and advice. It’s so helpful for someone like me who still has a lot to learn.

You are right, the tree was growing well. The soil just wasn’t ideal in my opinion nor was the container. The pines have reached a height where they tip over if the wind blows. I don’t like keeping them close together in order to allow light to hit the whole plant. Also, the containers were black which heats up quite a bit in the sun. I’m sure it would have been just fine in the soil mix for longer but I’m essentially trying to get the painful part out of the way, while the pines are young and resilient. However, I do realize there is still some of that old soil in there which I will have to deal with at some point.

The root work was (or at least appears) more than I wanted. This was both intentional and unintentional. The pictures don’t do it justice but for starters the container was less than 2/3 full of soil. Furthermore, the bottom half of the soil was really not occupied with any roots aside from roots than came down on the sides. I did trim some roots that were excessively long on the sides. The bottom of the soil container was covered in a very thin flexible screen material and the roots that came down the sides were kind of attached to that. I did not want the screen in the new soil so I had to remove it. Careful as I was there was just no integrity to the rootball and basically that bottom half of the soil kind of just fell off.

I tend to be pretty conservative but I only have $10, plus some wire, and some fertilizer tied up in this plant so not a huge investment. That’s not to say that I was reckless but I certainly was more aggressive here than I would have been with a tree of any significant value, like the one in your blog post. Also, this is an experiment for me. I have 8 other pines just like it. I intend to compare how those fare with this one and hopefully learn something. I’ve got 2 repotted last fall which are doing fine, this one repotted now, and 6 more. I may repot one more now, and then repot the rest in the late winter/early spring. It won’t be a controlled experiment or anything but hopefully i can glean something from this.

Please let me know if my thinking is sound or if I missed something of importance. Thanks again


(Jonas Dupuich) #8

That all sounds good to me Erin. It didn’t look like there were a lot of roots to start with so I’m not too surprised by the reduction of the rootball. And trying one of nine is a great way to start - that’s a much better data point than zero of nine. Do keep up the experimenting :slight_smile: