I have a Phoenix canariensis that sits on my patio from late april til' halloween or just before. Would your tree spend some time outside?

Washingtonia Robusta has to have sun or it will
eventually die.

These are fast growing large palms. Keep it in direct sun if you can and move it outside when the threat of frost has passed. Over pot it. Increase the pot size it is in 50% each summer until it gets too big to move.

They make for great patio palms! They love all the sun you can give them and a well drained soil. If you can swing it, they would also appreciate a nice cool location over winter. (Mine are overwintered in range of 40-60 degrees in a sunny, attached garage). My summer climate can be very wet (monsoon-like) so I don't increase pot size too dramatically as I want the surface to dry somewhat between waterings. Why do I love them? A few years back, I ordered a large variety of bare-rooted palms. All kinds of exotics from all over the world. Only, the seller didn't have any robusta in stock, so he kindly included a weed he had growing beside his house. It looked like a single blade of grass. All the bare-rooted exotics eventual died; the washingtonia is pushing five feet with enormously wide leaves.