I had a Ponytail Palm for 40 years. When I moved to Reno, it went to live with my daughter.
Anyway, mine spent summers outside and winters in my greenhouse. I watered it maybe 6 times a year. It was extremely rootbound but looked great.
I was using palmbob as my source (along with personal experience):
Baja, I will agree to disagree with you but still don't think they are native to the forest.
When I got mine, they were becoming endangered in the wild. I saw photos of them being hacked with machetes, slung on burrows and hauled out of the desert to be sold across the border. My attitude was that we should stop this kind of butchery but my mother had a different approach. She bought a couple of these black market babies (and gave one to me). Her thought was they were already 'harvested' so we should save them. Me arguing that they would not be taken out of the desert if no one bought them fell on deaf ears.
In 40 years, its probably tripled in width and my care has undoubtedly stunted its growth. But, as someone pointed out, do you really want them in a pot and 20 feet tall?
On the other hand, how fast do they (or any plant that naturally occurs in a less than ideal circumstance) grow in their native habitat? By taking any plant out of that sort of environment and giving it better care, better soil, more water and fertilizer once in a while, they will grow bigger faster. The only limiting factor at that point is genetics.
