I'm in Cali also...
I'm thinking either add some peat moss(holds moisture) to the soil or maybe something more technical.Like a buried resevour...or a resivour up in the trees camo from down below.That drips down from gravity.Not to savy with physics but I'm sure something like that should work.Up there watering will probably only need to be done every couple days...or have a light constant drip ? Just thinking out loud.