You need to long slow water that tree. 7 minutes is not nearly enough time. The best thing you can do for the long term on this tree is very very slow drip for 24 hours. I mean very slow. Barely trickling. and move the hose from time to time. You want those roots to reach deep deep into the ground so the tree does not blow over in a monsoon wind 2 years from now.

I planted two chilean mesquites in spring 2008. They are now about 30' tall with a very wide canopy, probably 30'. To me, that's a fast growing tree but when we planted them, hubby drilled holes around the tree's drip line, shoved pvc pipe with lots of holes into the drilled holes, he then filled liter soda bottles with water, screwed them into the pvc and let 'em go. Those are some very strong trees today. One of them lost ALL its branches about 5 years ago in a monsoon. Thought it was a goner but it came back, looks funny and is not as full as the other one but my point here is that all the branches were ripped off and the tree still stood.

Wow, great idea, thanks!!! When should I take the support pole out?

That's a tough one. Some folks say you should not use one at all but I'm pretty sure we did. Keep the lines loose though, if tied too tightly the tree won't move enough to build its core 'muscles'. If you don't use a stake at all, imo anyway, the tree may not be strong enough to keep itself upright. I would at least wait for this one monsoon season to pass. Pad the ties with something like old garden hose pieces or carpet scraps.

Those holes hubby dug were probably 3' - 4' deep. It's a lot of work. You can really just water carefully - deeply.

Water deeply, slowly, and not too often.Probably not at all after the first year. Mesquite will grow quickly if it gets a lot of water, but you will have a weak tree that will break in storms.

The big problem with forcing fast growth is that the canopy gets too big for its roots and the tree blows over.

You need to thoroughly SOAK the entire area under the canopy when you water, getting water down below the root ball, and 7 minutes with a dripper is not going to do it.

Make a basin that extends out slightly past the canopy and fill it with water, slowly and let it drain.

1 - Once a day for the first couple of weeks

2 - Twice a week for the first summer

3 - Twice a month for the first fall ... stop when the first frost hits.

Then it should be OK on its own, although if you want to speed up the growth, one thorough soaking of the entire area under the canopy and a bit beyond it (spiral a soaker hose and let it run 12-24 hours) after the leaves appear and about once a month until the monsoons start does wonders.

You are going to hate his next advice, but PRUNE the tree to shape and thin the canopy starting about now ... Leave the lowest branches, but cut them shorter to encourage branching ans more leaves closer to the trunk. Eventually you will prune them off to raise the canopy

Don't let it get long floppy branches ... they make for a weak tree.

Yup, I agree about deep, infrequent water, and about them growing too fast with too much water. I'd give a youngster a good deep soak every week or two the first year, then maybe once a month the second year. I've been blessed/cursed with large mesquites at both of my Phoenix area gardens, LOL. My current tree is one of the largest I've seen and I eased it off of any supplemental water during my first two years here. Now six years later with no water other than rain it still looks great, grows nicely, but doesn't make that lanky growth that required frequent pruning early on. Love yours, Mary! So great. They are actually pretty decent trees when not grown too quickly or over watered. Happy gardening all!