For the average person and garden, Puya Alpestris is the better plant to raise. Berteroniana is a huge plant, probably better on a hillside. Alpestris only gets to about three feet wide and the flowers grow about three to four feet high. The flower display is similar. Photo attached.

Yes, I have drainage holes :) If I am going to the trouble to create a well drained and structured soil, then be sure I make sure the container has drainage holes, covered by a large particle screen.

The current state of my own Puya Alpestris are in the second photo.

They grow them at the Huntington on large mounds above grade amended with a lot of scoria. They happen to be in bloom right now too, from last week.

I have Puya ferruginea on a sandy slope in the ground and in a dry gritty. They need hardly any water. The ones in the ground are in 6" of sand over bedrock on a southwest facing slope. I water once a month in the summer (15%ET0). I had another one that I took off irrigation and hit it with the hose occasionally, but it's overflowing the pot. So hardly anything actually gets in.

I would try it in another type of unglazed terracotta pot. Then it could dry out faster and oxygen permeate the Terracotta to reach the roots. It is hard to tell but it appears your pot has a coating over it.

@harold100 That's an interesting point. My pot does have a painted surface. How does air normally flow into these pots? Isn't it the plant respiring that sucks air in, and if yes wouldn't they be able to grab O2 from the surface soil?

I am not a pro at growing such plants, but I remember a knowledgeable person on here warning against using the glazed pots.

Air gets to the roots when you water. The cascading water draws air down into the medium. Unglazed Terra cotta dries out faster necessitating more frequent watering and thus more air exchange.

Have not had any problem growing P. berteroniana on steep, hot, arid slope. No irrigation. Have not gotten a flower yet, though.