It’s been a couple of years since I repotted my big Willow oak, Quercus phellos. Last year I named him Rip Van Winkle, because he waited until May to finally bud out. (I was afraid he was R.I.P. Van Winkle.) Anyway, when I did the repotting back in 2016 I tried something different when I went back into the pot, namely, I added a drainage layer of pea gravel to the bottom of the pot. I didn’t have any firsthand experience to know if this actually does any good for bonsai – after all, we need to prepare soil that’s free-draining before we even consider potting up a tree. But I was willing to give it a try.

Willow Oak - Quercus phellos

The first question you may be asking is, Was it really necessary to repot this tree after two years? The best answer I can give is that what goes on below the surface of the soil is more important than what goes on above. Don’t forget, we’re expecting trees used to growing in open ground to survive and thrive in a small, shallow space. This means their roots cannot travel where they need to go to gather water and nutrients. We provide an environment in the pot designed to give oxygen, water and those needed nutrients as best we can. When the tree grows roots, the spaces that allow for sufficient water and oxygen get filled with roots. Eventually, there’s just little to no soil left and the tree won’t stay alive under those circumstances. Now, does this happen after two years? For most species, no. But there’s no reason not to pull a tree of this age (40+ years), especially considering how late it came out last year. Plus I know from the last repotting that Mr. Van Winkle grows a lot of roots in a short amount of time.

Willow Oak - Quercus phellos

My first step was to loosen the securing wire, remove the training wire from one of the branches and clean the trunk with vinegar-water (white household vinegar and water mixed 50:50) and a toothbrush.

The bark on this tree is very tough, so I was able to give it a good scrub. I also have done some light pruning, being careful not to trim the lower branches too much as they still need to gain heft.

Willow Oak - Quercus phellos

Here’s the tree after I pulled it and removed the pea gravel that was in the bottom of the root mass.

Note: I didn’t see any indications that would suggest a drainage layer improved the growing environment of this tree. There were roots in among the gravel, which is exactly what you would expect. As for drainage, a shallow pot like this one can only produce so much hydraulic head to cause the water to drain; a drainage layer of less than 1/2 inch doesn’t really change this significantly.

Willow Oak - Quercus phellos

Here are the roots, combed out and trimmed. You can see the really nice radial roots.e.

Willow Oak - Quercus phellos

Going back into the pot. One thing I’m doing at this repotting is to raise the tree slightly in order to better display the nebari. This is one of the key things to bear in mind when you work with collected trees (those you get from me, for sure). It’s always best to bury the radial roots, as this will keep them from drying out as the tree recovers. To be sure, you want to display nice roots on your trees, but from a practical standpoint it’s more important to keep them alive in the beginning than to be able to see them. In time they’ll be revealed, as in this case.

Willow Oak - Quercus phellos

The dry soil has been worked around the roots using a chopstick, to fill any gaps. Gaps in the root zone = dead roots in that area.

Willow Oak - Quercus phellos

This is the same picture as the very first one you saw in this article..

I’ve placed it here for you so you can have a birds-eye comparison of how it looked when I started and how it looks afterwards (that’s the photo to your immediate right).

Willow Oak - Quercus phellos

The final result for today, after a thorough watering.

If you compare this photo with the first one (to the left) you can see that I’ve revealed a little more of the nebari, making the tree look even more impressive than before.

Now I’ll wait for it to leaf out, so I can continue its development.

Let me know what you think of today’s work.

Note:

Comments are closed. Remember to use the new Insider’s Club Form to post your questions and comments. This helps everybody learn and help and this is where I am now posting responses to your inquires and comments. (You’ll find the forum by scrolling up; it’s on your right.)

6 Comments

robert gardner on April 6, 2018 at 9:32 PM

Zach,
What a remarkable tree to work on. As for the pea gravel I do believe that you were quite correct to use it. I don’t use pea gravel for my drainage but a lot of Pumice as it drains well and holds moisture. All my Ponderosa pines and JBP all seem to love it.
Right now I am going to start re potting a rocky mountain oak I hope to find some good
size roots to bring to the surface. Never worked with these or any oaks for Bonsai.
This oak is about 10 years old and it is in a 1 gal\. nursery pot.
Any ideas.
- Zach Smith on April 7, 2018 at 7:44 AM
  
  Thanks, Bob. As I said, I was not able to ascertain any difference using the drainage layer. But that’s hardly science. To test the theory would take a properly sized sample population of trees as close to exactly the same as possible, grown side by side with a control group (no drainage layer). Otherwise it’s just empirical observation.
Pierre Kaufke on April 6, 2018 at 4:34 PM

That will be a master bonsai in very little time. pk
- Zach Smith on April 6, 2018 at 4:35 PM
  
  Thank you, Pierre. It is probably in the top five pieces of material I’ve collected in 30 years. A remarkable specimen.
Mac McAtee on April 6, 2018 at 4:01 PM

Quite a nice prize you got there Zach! I think next year you can raise it another 1/2″ or so when you repot.
- Zach Smith on April 6, 2018 at 4:02 PM
  
  I think you’re right, Mac. Step by step.

Repotting Mr. Van Winkle

Willow Oak - Quercus phellos

Willow Oak - Quercus phellos

Willow Oak - Quercus phellos

Willow Oak - Quercus phellos

Willow Oak - Quercus phellos

Willow Oak - Quercus phellos

Willow Oak - Quercus phellos

Willow Oak - Quercus phellos

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