My property has over 100 joshuas on it. This is my opinion, but I'm not a horticulturist or anything. If one of them weighs in, please go by their recommendation!

I would mist it once a week in the morning -- I think they get the majority of their water through dew. It really only rains here between October and April and we only get 5 to 7 inches total a year. Their roots rot very quickly.

Morning sun. They do better here when they have a nurse plant -- something that blocks the sun during heat of the day. But it's going to be 95 today here and the humidity is 14 percent. In Wisconsin, maybe stick it in a sunny window all day with something to block the late afternoon sun.

If you don't already have it in sand, you might want to consider that. They don't like nutritious dirt. I can send you some genuine Mojave Desert sand if you pay the postage. But I'd think sandbox sand would probably work. And you may want to put it in a big pot. Their roots like to spread out a lot.

Good luck! It's difficult in the Midwest. Even the joshua in the Morton Arboretum in Chicago looked unhappy when I visited last.

We keep ours in containers, and just water them like anything else--let the soil dry out a couple of inches down before watering. We found they are easiest to kill by keeping them moist while stored in the garage for the winter. I started some more this year that I plan to try planting out in the garden next spring.