I trunk chopped a Chinese elm and in another year or so, I'm hoping it is ready to go into a training pot with the roots tied to a rock and once they are ready to be above the soil, I will put it in this pot. The dimensions I don't know exactly, but it is about 18 inches wide and about 2.5 inches deep and about 9 or 10 wide the other way.
Nice. I almost bought an elm when I was on vacation...one of these days.
This is what I think Rock was talking about
Plastic like, but similar size 18" long and 2.25" tall with shallow feet.
It was manufactured with 5 drainage holes, I added probably 8 more for wire.
If you were only hand watering your tree, and not in a rain prone area
a single hole just may be what the conditions need. If you ever were to drill this,
it would be best to have the underside perfectly supported with an even drillable wood base
to support a glass drilling bit like a circle with diamond tip is good. The wood will still support
the pressure of the edge as it comes through. A light continuous flush would be beneficial too. Clean.
I believe these 2 pots are similar to yours but rather small so a single hole it is.
The oval had a black olive in it at one point in my past. If they had stickers on them, they're long gone,
but no stamps on either style. They would not do well outdoors here if in use.
The oval, why I pictured it, though only 8.5" L, has 2 drainage holes. I hope to have a maple in it one day.
Oh, and the in turned lip is definitely not good for freezing either.