Training Pot Rule of Thumb

kompik

Many things I've read suggest using a training pot as an intermediate step between the tree from growing in the earth or in a nursery pot and the tree's "final" bonsai pot. Since I've got some time before spring rolls around and I start root pruning, I'm doing some shopping for suitable pots for potential bonsai material I've collected over the past year and I'm wondering...

Is there a rule of thumb about how to size a training pot in comparison to the tree's root ball or nursery pot?

For example, I have a nice-sized juniper that's currently in a 1-gal. plastic nursery pot. Approximately what size training pot should I be looking for?

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Globalist1789

Basically, the bigger the better. But it also depends on how long you hope to take before it is "finished" and ready for a small pot. If you are only planning to train your juniper for another year, perhaps two, before moving to a smaller pot then planting it into a larger pot would be a counter-productive. Junipers are tough. One the other hand, if you are training a something that is going to take much longer, then planting into a very large pot and not needing to repot it for 4-5 years might be just the ticket.

rockm

The bigger the better is not better . Using a training pot that is huge compared to the root ball can make for soggy soil and waterlogged roots and root rot. The roots can't colonize the huge volume of soil in a huge container, leaving excess water. This is especially true for conifers, since they don't push massive amounts of roots as some deciduous species do, so that space will be vacant for some time.

My rule of thumb for training pots is to go about a third larger (maximum) than the rootball. There really shouldn't be more than couple of inches of room on the sides and on the bottom. An inch would be great, for your juniper, I'd think.

Colin Lewis

One of the most important considerations of a training pot is the shape. Remember you are training the roots as well as the branches.

I use plastic terracotta colored bowls - the kind that garden centers use for pre-planted hanging baskets. It's easy to drill a few half-inch drainage holes and the lipped rim is handy for tie-downs. The wide surface area means that fertilizer favors surface roots and watering is easy, while the bowl shape ensures all excess water is channeled straight to the drainage holes.

Japanese growers use similar shaped containers, but ceramic, naturally!

Now's a good time to shop around for these while demand is low and they're cheap. If you wait until spring to buy them, the price will skyrocket! Bowls that I spent $16 each for last May are now priced at $3.50.

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