I have had a Mexican Fan palm almost 20 years. It should probably be about 30 feet tall now. After a year of being in a pot, I took it out and cut back all the roots leaving a smaller ball of roots under the trunk. I thought it would die but it didn't.

I think the effect it had was to turn it into a sort of bonsai palm. It still looks like a Mexican Fan Palm, it just doesn't get very tall. It's about 3 feet tall now. The trunk is about a foot and a half tall.

I don't know if that would even work for a windmill palm but it worked for mine.

One of the problems I had with my windmill palm was too much moisture. I don't know for sure that that was the cause but we got a lot of rain one summer and I had it outside in a pot and the spear rotted. Maybe someone else on here can tell you if they are susceptible to crown rot from too much rain. It seems like that was the death of mine.

Trachy can be kept in pots forever. They will also make bonsai like palms. If you notice one of the best potted palms- the Rhapsis palms,look very much like clumping Trachys.

I have a Butia in a 14" pot. Been in it ten years..never did anything but water it and toss on the root ball a few handfuls of soils as the old gets washed out over the years. I like the recurved fronds without having a big palm.

Interesting. I wonder if that would work with a date palm?

I kept a trachy in a 15 gallon pot for several years. I also kept it on the dry side - just enough water so the leaves would not brown. It stayed under 3' and barely grew. Later, after I planted it in the ground and watered it generously, it shot up to about 15' in eight years. So yes you can stunt a trachy by keeping it in a smallish pot and keeping it on the dry side.

Trachys will not grow very fast in pots (in the ground they are fast growing under great conditions but pretty average growing palms normally). I have seen trachys do beautifully in pots for their entire lives. Eventually it will get bigger than 3-4 feet but my best advice is to keep it in sun (once the plant is well adapted to sun). The fronds will grow shorter in sun than in shade so it will look much more compact but not stiff like wagnerianus.

Good luck!