In zone 8, I would put it in the ground and mulch it heavily. If it was growing in your area I'll assume that its hardy there. Let the cold kill the leaves back and then use them as natural insulation around the trunk (bend them after they freeze back) then wrap frost cloth or a blanket around the trunk if there is going to be a freeze. If the trunk gets hit by a freeze (turns to mush) cut the mushy part off and continue wrapping. Your main goal is to protect the trunk as much as possible, if you don't cut the mushy part of the trunk off it will spread down and rot more of the trunk. I have photos I could email you of mine and what I'm doing with them (I have about 50 in the ground) I am in the same zone as you.

the only problem with buried rotting wood.. is that the rotting process ... requires water.. and it can cause dryness in the surrounding area.. all you need do.. is insure PROPER WATER.. which means insert finger and water when dry or hot under the mulch [which means it will soon be dry] ... water deeply.. thru the root mass .. and then dont water again until it nearly dries... now.. presuming you did not plant right next to 6 inch roots.. i really dont think that is relevant .. for the general area ... rotting can also rob the soil of nitrogen.. but again.. how close could you have planted ... if and WHEN you get a plethora of shrooms.. from the rooting process.. enjoy them for the show ... they are just part of the decomposition process ... IMHO.. in any average soil.. trees/conifers. never.. ever NEED anything ... though a little of this or that probably wont hurt ... chams in my z5.. are VERY slow.. all things considered ... and it probably has a lot to do with the frozen ground for 4 to 5 months ... ken

1. If you can stand it and have some patience, repot your clematis in a next size pot for this year. Clematis need to establish really good root systems and it sometimes takes anywhere from 2-3 years. Growing it in a pot the first year encourages the roots to grow. 2. Clematis likes cool roots, so much it very well. 3. Fertilizer: I've used tomatoe fertilizer (most popular a few years ago), chicken manure (contains more phosphorous than steer manure, and feeds your soil), and the new thing is alfalfa fertilizer. 4. Know your clematis group - there are 3 groups, and you can check them out by googling "clematis groups". I checked and yours is a Group II - repeat bloomers; prune immediately after flowering to the next good node. 5. Support: I have planting mine against my chain link fence; by my deck to which I stapled some fencing for climbing; and by use of trellising. They climb by "twining" so you may have to give them a little help with "stray" stems. I saw some humongous pots of this clematis (with humongous flowers) at Horn's this week. I don't know how much they were - they probably wanted my first born child for them. But they really are gorgeous! Congratulations. It's easy to get hooked on them. I have a few - 'Nelly Moser', 'Dr. Ruppel', Jackmanii (a very good grower even in partial shade), 'Polish Spirit'. I used to have C. tangutica because I wanted a yellow flowering clemmie. It was just too rampant and I pulled it out. However, there are some cultivars of tangutica that aren't probably as rampant as the species. I love some of the "bell-shaped" flowering clems, like Rogoochi. And there are also some beautiful "shrub" clematis as well. The possibilities are endless if you fall in love with these guys. Susan

how big are these trees?? it is said the root mass.. in the shape of a flat pancake can be twice as big as the tree you see above the ground ... the feeder roots may not even be in your yard ... which is how big??? .. break down 1800 sq feet ... its too early for me to figure that out ... im presuming.. you did not shave off the lawn.. just killed it and then mulched?? well established trees should not need any water ... so your lawn watering was just a bonus.. of course.. there might be.. in tree time.. some years of adjusting to the new circ's .... but im not sure there is anything you need to worry about .. maybe in severe drought.. give them a decent drink ... cant hurt .. but do keep in mind.. you did mulch ... and that should help retain moisture in the soil ... what did you mulch with ... and i presume no landscape fabric was used?? ken