Colin - if it's already in a pot, then anytime will do. Pick a pot at least 2 in. wider in diameter than the pot it is in, and a couple of inches deeper. You can also go with a bigger pot than that, just be sure that whatever pot you shift it into, it won't stay too soggy - wet roots will rot and kill it off as fast as anything else. If you want to plant it into the ground - while it will live and grow in a pot, it will do a LOT better in the ground - as long as you are prepared and willing to water it at least an inch of water per week, maybe more, depending on how it looks and how hot it gets - then any time will do for a potted plant. If you have really hot summers, you might do better keeping it in a pot, in a slightly shady spot, over the summer, and plant it in the ground as the weather cools off in the fall. Gorick, I would agree with the two posters above - moving any tree that large is a job for professionals with heavy equipment, never mind moving 5. You might well be better to start over again with smaller trees, rather than stress these, and your budget, trying to move them. If nothing else, they will take a LOT of watering over the summer for them to settle in and to survive. I'm not saying it can't be done, but this time of the year is a bit late, and it WILL cost. You might call around and get estimates from a couple of tree services. Try to get those who are certified - their will be more reliable. And, of course, check on references, insurance, that they OWN the equipment, not rent it, so there is a likelihood that they have done a number of BIG jobs, etc., etc. You know all the questions, I am sure, it's all the usual part of doing business. The other thing to think about is whether there would be access to the site the trees are on for the necessary equipment - there would have to be a big tree spade machine, a crane to lift the trees (also large), a large flatbed truck or two, and a Bobcat or dozer to fill in the holes, plus its transport, at a bare minimum. You would also need access to the site where you want to plant the trees for most of the equipment. People have been moving large trees for hundreds of years - I have seen photos from the late 1800s of men with shovels and several 4-horse teams of horses, moving an oak tree that dwarfed them, in the middle of the winter. I am sure it cost big bucks then, too, but it IS doable.

Nope, as far as vents, I don't recall seeing any windows either. I do believe if you click and see the pic I posted a link to, that there is one more pic of the tree/house in my photo library. I walked through it, and it is very tight quarters, and was built in the 50's or 60's. A Logger lived in it for several years. I'll post the other pic, which will be kinda the same as the 1st pic, no vents shown etc. Here it is: Other Sequoia house No new fangled stuff on this 50+ year old Sequoia trunk house.

I'd agree with smivies and kentrees that they probably won't be very happy at the OP's location, or in much of the eastern US. See the last 2 posts by sam_md in this thread: http://forums2.gardenweb.com/discussions/1736468/baby-giant-sequoia-in-winter?n=30 The tree pictured in the link below is growing near the Lake Michigan shoreline, and it seems to be doing well. It apparently benefits from the lake effect snows (and moderated temps) at that location. 95' tall, planted in 1948: http://midmichigannatureandscience.blogspot.com/2015/08/field-trip-michigans-largest-giant.html

Dawns grow to 100' height in 30 years, Giant Sequoya 250' and about 2"/year increases in trunk diameter. While you can enjoy them in pots for some time, they eventually will outgrow them. The fine feeder roots are sensitive and break easily, so it's best to always avoid disturbing them when transplanting to a larger pot which you may have to do at least every two years. Fertilize only during spring and summer, but not immediately after transplanting, fertilizer should not be applied while the tree is stressed.