In my experience, Washintonias need lots of room for their roots to get to any decent size, otherwise they seem not to grow much at all. I would think you could limit it's growth by limiting pot size. But with a 15 gallon pot, it probably won't get much taller than 6 feet.

Interesting. Do they have strong roots that can crack the pot? I really don't mind to 'stun' the poor palm (please forgive me, palm lovers) if this is what it takes to slow down it's growth.

Excuse me Im just still drooling at the thought of a 6 foot Calif fan for 20 bucks.

Same here, I am buying a couple unless this guys grow 2 ft or so every year. Do they grow that fast in pots but under ideal climate?