Those of you who have been with us for a while know I love to slip-pot trees. Why? Well, I guess the biggest reason is I’m impatient to see a tree progress toward its best self. Another reason is that a lot of trees pass through my hands, and often it’s just time to go ahead and get a tree into a bonsai pot and move on to others. Slip-potting usually saves at least half a season in terms of getting a tree to a good showable state. So there you go.

With that said, however, there are some rules that have to be followed if you want to see your trees progress faster to your ultimate goal (meaning the slip-potting has a positive rather than negative outcome). Here are some I adhere to, in no particular order:

1. The tree must be healthy with good vigor. I know, this goes without saying but it never hurts to bear it in mind.

2. The tree either has to have a complete trunk line, or be vigorous enough so that you can complete your trunk line in a bonsai pot. Shallow pots slow growth, always.

3. You need good roots. Foliar vigor isn’t always reflected below the soil, and this is especially true for species that don’t grow roots quickly (such as hollies).

4. The pot your pre-bonsai is growing in should be very similar in size and configuration to the bonsai pot you intend it to go in. Which is another way of saying you want to avoid removing any roots, to the greatest extent you can.

5. Only slip-pot when there’s time in the growing season for the tree to recover from the move. Or, put another way, don’t slip-pot in winter. That leaves three whole other seasons, so you should be able to get your fill of slip-potting while it’s warm.

My first step was to do some light trimming. I pruned the lower branches pretty hard – they’ll push some more growth in the next four to six weeks, which I want. I also pruned the crown more or less to shape; again, light trimming.
Now let’s look at some numbers. First of all, this specimen has a 2.5″ trunk base and is 33″ tall. This is a good ratio for a flat-top BC, because they look best with tall slender trunks in the “tall tree” form. The 33″ height gives us the guidance we need for a suitable bonsai pot. You don’t want the pot to be longer (or, if a round, larger in diameter) than about 40% of the height. The diameter of the nursery pot is 13″. My bonsai pot needs to be that length or slightly longer. This is good, because I won’t have to cut any root to make the tree fit. The depth of the soil mass is about 3″. This too is good, because I want my bonsai pot to have a profile depth roughly similar to the diameter of the trunk at the base. This means I don’t have to cut any root off the bottom of the tree.
Here’s how the slip-potting turned out. I had a very nice Byron Myrick oval on hand. The length is 14″ (outside edge to outside edge), and it’s 11″ wide. I was able to easily fit the tree into this pot, meaning no significant disturbance to the roots. And finally, the pot is just over 3″ deep in profile, which was the depth of the soil mass. It was very easy to get the tree into this pot and fill in with bonsai soil. With four to six weeks left in the growing season, this tree should continue to thrive. I anticipate seeing some nice fall color, which should go well with the pot. Let me know what you think about today’s work.