It is hysterical that folks think they can straighten trees this way–simply not possible! Those t-posts are too weak and that tree would need massive 4 x 4 posts planted at least 2 ft into the ground. Heavy gauge wires would be required, too. Save yourself the trouble. Save yourself from looking like an idiot!
It drives me nuts at how many new landscape plantings have leaning or crooked trees, but I know why it’s happening, for two reasons. First, in commercial plantings, where big landscape installers do the planting, they use heavy equipment with huge augers, and the root ball has “way too much room” in that hole. Then their workers backfill the holes without tamping/firming the soil around the root ball. Thus, the tree is free to flop around in the wind. It is especially bad with evergreens because they present considerably greater wind resistance than deciduous trees.
Now you’re thinking, “OK, Jeff, what should I do if my tree is leaning?” Well, first of all, when you plant a new deciduous tree or evergreen, DO NOT use “great soil” to backfill the hole. Use your native soil, or amend it just slightly to improve it; avoid using that fabulous “bagged dirt” with peat, compost, vermiculite, etc. That stuff won’t compact and your tree will flop in the wind. If you have nothing but rocky soil, just use plain ‘ole bagged topsoil as backfill but use as many of the clay crumbs as you can.
Reason 2 for crooked trees, for the average Joe. What I will say next is sure to piss off the PROS, like the university extension folks, the master gardeners at MoBot, and the published authors–DO NOT make your hole “twice as wide” as the root ball. This will give you a floppy tree for sure. Dig the hole about 1 to 2 inches more shallow than the root ball because you do not want the crown of the plant to be lower than grade (potential rotting issues). Dig the hole only 6 to 8 inches wider than the root ball, just wide enough to use your foot on all sides to tamp the soil back into the bottom third to half of the root ball. As you backfill the hole, continually insure that your tree is straight on ALL views. Make sure the more critical spouse is present during planting, so that the new tree is perfectly straight. I’ve planted hundreds of trees this way and seldom had a crooked tree! If your tree does lean, you’ll need to fix it ASAP. Don’t just push on the tree trunk, though, and for goodness sakes, DON’T STAKE like this photo. For example, if the tree is leaning 10 degrees due north, you’ll have to dig up some soil on the outside of the root ball on the north and the south sides. For this example, use a spade on the north side to pry the root ball sufficiently so as to level the tree trunk. Then tamp the soil EXTRA firm with your foot. Digging on the opposite side (south in this example) facilitates repositioning the root ball. Tamp the soil back in on the opposite side, too.
SIDEBAR: don’t remove the burlap from the root ball, or the wire basket (if present). Cut the twine off of the tree trunk, to avoid girdling the trunk. Make sure that burlap is not exposed, because it will wick water from the root ball. I recommend cutting the top of the burlap off AFTER the tree is planted.
And oh, by the way…cut that ugly tree down!