A friend of mine planted about 100 Green Giants about three years ago. They were about 18-24" tall when he planted them. Green Giants are pretty deer resistant, but where my friend and I live there are just too many deer in a small area (island) for that to mean much. The first year he planted these 100 Green Giants, the deer destroyed about 25 of them. After he replaced them, I recommended that he start using Milorganite fertilizer around the trees to keep the deer away. (It's an unadvertized fact that Milorganite acts as a deer repellent.) He started dumping Milorganite around the base of the trees on the perimeter of his property and the following year those were nearly 2ft. taller than the other trees (same growing conditions). Needless to say he started using it around all the Green Giants and this year some of the ones that he started using it on first are taller than me (6ft.). I started using Milorganite on my lawn a few years ago to keep the deer away that were eating my plants and it did wonders for my lawn. I started dumping it around all my perennials, mixing it in with the potting soil for my annuals, and tilling it into my vegetable garden. Everything improved! The stuff is like the Frank's Red Hot commercial... I put that s*#& on everything! I'm not sure it's the "best" fertilizer for your Green Giants, but it's definitely good. In the past I was always afraid to fertilize because I'd overdone it too many times and killed/burned too many plants and lawn. Milorganite is organic, so you can't really use too muich... it will just sit there on/in the soil until the soil microorganisms can consume it. Good luck!

go out there... pull back the mulch.. and use a hand trowel ... and at about 2 feet out.. dig a 6 inch hole ... AND FIND OUT IF ITS MOIST DOWN THERE ... it sounds like your dude is guessing ... the root ball planted should stay moist for about two years ... because of the large size ... so find that root ball .. and find out ... then water accordingly ... with that thick mulch.. once you find out how the water is working you your soil ... water deeply .. and then dont water again .. until the soil is near drying ... again.. dig some holes .. never the same one ... it would not surprise me.. if that was once every other week for a couple hours ... but the problem is.. if your dude guaranteed them .. and after all.. he is local ... you should err towards doing what he said ... based on the warranty ... but i would still dig a few holes ... and FIND OUT... so you can have an informed discussion with him ... ken ps: if i ripped your roots from the earth.. trucked them across the area ... dragged them across the yard.. and planted them ... i would expect some stress ... like browning of some of the tips ... dont try to love them to death ... just water properly ... see link for a discussion ... and for sure.. they are NOT hungry ... no fert . and seeing that lawn. once they get roots out there.. they will get all the fert they need ... https://sites.google.com/site/tnarboretum/Home/planting-a-tree-or-shrub

I love walls of emerald green arborvitae, especially their texture, color, and fullness/density. Here is a pic I took about an hour ago at Muirfield golf course(Memorial tournament). Love the wider spacing, this is gonna be a killer wall in 10+ years(road is to left of bike path, need to focus on putt). Looks like they disregarded the internet, which generally suggests 2’-3’ spacing for wall, when deciding on spacing(check out the dead one). If Jack Nicklaus approves Thuja Occidentalis Smaragd as a privacy screen, then they must be good lol. Id say 21, 5-6 footers for 850 is a good deal. Still small enough to “become one with the ground/established” rather quickly. Even the 10+ footer I planted 5 years ago did good, though the smaller the tree, the quicker they get established. I have seen tiny tots outgrow larger trees on more than one occasion. I didnt believe what people were telling me until I witnessed it. All the $5, 1.5-2 foot Smaragd I planted 4-5 years ago are gettin close to 5’, some might be more. In looking at the pic, and knowing that there are lots of deer here, (some of) these may be getting deer pruned, though just a bit. The right two perhaps.

when the goal is sight block.. you plant them to achieve your goal ... when you are planting individual specimens ... then you plant them further apart ... if the former.. you want them to grow together asap ... in the latter ... you plant them so they maintain.. to some extent .. their individuality ... 8 foot on center.. means that each tree need only grow 4 feet toward the other ... and that isnt much.. for these... GIANTS ... and frankly.. imo.. there is little difference between 5 or 8 feet .... 2.5 feet each vs 4 feet ... and with these GIANTS ... once established.. that might be not much more than a year or 3 ... depending where you are ... the length of growing season ... frankly ... you are over engineering the concept ... rather than gardening the concept ... when it all boils down ... lol .. you might be better going off with what wifey said .... this probably isnt where you should draw some line in the sand ... and keep in mind.. with trees.. we think in tree time .. which is counted in decades ... it will take them a year or 2 to settle in from transplant shock ... and then a few years to start putting on the height you want ... which is the norm .. just dont go all instant gratification on them.. and it should all work out ... ken