I recently bought 2, 7 gallon Robelini Palms to plant in my back yard in Las Vegas, NV. I've never planted Palms before. Can anyone tell me how deep and wide the hole should be and what kind of soil prep I should do? I am planting them in an area which currently has grass. They will be getting a lot of sun as the back yard faces west. How much water do I need to provide (I have a bubbler system). Thanks for any and all help!