The Catalpa will need its own pot, as will the Empress.
The Empress may grow slightly faster, but the Catalpa is a better-looking tree and a fast grower in its own right.
You may want to be careful about planting an Empress tree in Florida. Several southern states are listing them as invasive species not recommended for planting.

Coyle mentioned growing these as container trees. As such, assuming the trees will not be allowed grow too large, it would be a fairly easy annual project to deadhead, or remove seed pods (if indeed they ever flower at all!), thus avoiding the invasive issue. Indeed, with some methods of pruning, they may never bloom. Paulownia can be managed this way as foliage plants; ie, severely pruned annually, allowed to grow really huge leaves on juvenile stems, and never allowed to flower.

I grow Catalpa in containers as foliage plants. They will tolerate severe pruning, including pollarding and coppicing. I believe Paulownia will tolerate the same treatment.

Cheers.

Does the Catalpa tree flower when grown in a container?

Thanks redneck grower; nice to know they can be grown as container trees as that's what I want. The empress, well since they are coming up if they survive this summer (which they seem well on their way to doing) I will give them their own pots. The catalpas are my babies though. I don't care if they flower, I just like the foliage.

"Does the Catalpa tree flower when grown in a container?"

Only if the container is absolutely huge (containing several tonnes of soil).

Resin

No, I don't expect it to flower but it sure is taking off.
If your results are like mine the first year it will just hang in there but after cutting it back to the ground, the second year it should really explode! I'm getting growth daily now. The empress trees are in their first year but are also getting daily growth. I can't imagine what to see from them next season. I will transplant this fall and give some away and maybe make 2 more pots of each. Plenty of time to decide.

pineresin wrote:

"Does the Catalpa tree flower when grown in a container?
Only if the container is absolutely huge (containing several tonnes of soil)."

Yeah, I'm not sure either if a containerized Catalpa will ever flower. Mine never have, though they are only 3-4 years old now (and I believe Catalpa's only flower after many years? Correct me if I'm wrong). However, we know that normally-large trees that are trained as bonsai can eventually flower, so I guess it is possible that a containerized Catalpa may flower also.

But, don't take this to mean that you CAN'T grow a Catalpa for many years in a container. One simply needs to adopt some of the principles of bonsai culture to "train" a normally-large tree to grow in a relatively small container. Containerized Catalpa will need regular top AND root pruning to keep it in scale, and keep it healthy.

When I do the root pruning will the leaves get smaller like a bonsai? Because the reason I picked the northern catalpa is for the attractive larger leaves or I could have just grown southern catalpa which do nothing for me. Mine are really taking off and I'm thinking of transplanting soon & giving my neighbors some of them; especially the empress trees; should I wait until fall (when they will assuredly be rootbound) or can I do it now with summer pretty much here?

giving my neighbors some of them; especially the empress trees

Please don't give your neighbors empress trees unless they are also going to be treating them as bonsai/potted plants and therefore not allowing them to grow large and set seed and contribute to the problem in the South.

Here is an earlier thread about bonsai and leaves being smaller.

Here is a link that might be useful: Bonsai thread

"When I do the root pruning will the leaves get smaller like a bonsai?"

I'm no expert at bonsai, but I don't believe by root pruning you will reduce leaf size. If I understand plant physiology correctly, your leaf size may reduce if you DON'T root prune; ie, constrict the root zone, as in bonsai. Root pruning will keep the plant vigorous with big leaves.

Having said that, I've heard that Catalpa and Paulownia don't make good bonsai candidates because you CAN'T reduce leaf size very easily.

Somebody chime in if my suppositions are incorrect.

Cool, I hope that the leaves stay large! I just pruned the roots of 2 catalpas and put them in smaller pots. I still have 2 unpruned ones in a larger pot too.
(Both the catalpas and empress trees are only for containers.)