I'm from the Antelope Valley. Fruitless mulberries get huge..fast. I hope you have a lot of room. I see people with the trees out here along the sidewalk(between the side walk and street) they are tearing up the sidewalks! If it is next to any structure there will probably be damage. Anyway, very fast growing trees take up a LOT of water. I don't know what's on your tree's leaves but it's probably signs of stress. They need to be deep watered once a week at least. Shallow infrequent waterings(sprinkler only etc....)lead to a very weak tree. I'd also cover the base with 2 inches of compost and 2 inches of mulch to add nutrition and hold in water. Do not make a "hill" around the base of the tree. Spread the mulch evenly in a circle the at least 4ft out. The high desert here starts at 2,000ft. We have 40 degree fluctuations in temps. in one day.a good way to test for watering is a piece of rebar. If it's muddy and wet 1 1/2 ft down you're good. If it's dry deep water. Don't plant any plants around the base...it will weaken the trees. Hope this helps.PJ