a bit more ambitious endeavor, running water too

There will be no running water in mine. I will heat with light bulb and a Pelonis disc heater.

Steve

bklyn - are you going to do anything to secure that window up on the top of the structure (a weight or strap)? Also is it semi-deciduous in there during winter? Was looking at some info on those (and other trifoliates) and that is what has been noted. I have also seen that flying dragon will be deciduous in cold winter areas. I have 2 non-citrus shrubs - an itea that is semi-deciduous and a honeysuckle that is semi-evergreen, so it's sortof an interesting characteristic in any case.

No, that window wont go anywhere, always could put a brick on top. It did not drop leaves last time I had it out 2 years ago, I've heard they do drop leaves and that they don't. I won't cover until its dormant.

silicone caulk will hold better than a brick and won't block light.

Steve

Okay cool bklyn. And Steve - silicone caulk is a good idea. Have used my share of it!

In my climate (zone 8a, south of Seattle), cold-hardy citrus (like citrangequat) can survive over the Winter in just a frame wrapped in clear plastic sheeting, if it's in a sunny location. Especially if you keep several large containers of water inside to help regulate heat between day/night. I know the East Coast climate is very different but this might work in your zone 7b if you are in an urban location and feel the planting spot will not be quite as cold as its surroundings. I'm talking about in-ground citrus, and it's important to point out that in-container citrus does not have as much hardiness. This is because growth is less vigorous because the root system has a limited area, and also there's less insulation between the roots and the outside, so the vulnerable root system is more likely to freeze if it gets cold.

The Pacific Northwest has an unusual climate and it is sometimes possible for the cold-hardy varieties of citrus to be able to survive outside completely unprotected (on the border of zone 8b/8a, and sometimes zone 8a, usually if located in a good spot, and the plant has had a chance to grow out a bit before going in the ground).

There might be that rare Winter that comes along every so many years where they will need some light protection though.

I'll skip the caulk in case I more easily want to dismantle or remove it, I had a similar setup last time. This is a sunny location especially in winter, Southeast/west during afternoon. This very same tree did survive in that same location (I pulled and potted in Spring) in a plastic only wrapped frame when it was 2 years younger, pruned shorted and planted in ground in Fall, this was put in ground in Spring, I will frost cloth it. In any event, I have a top cutting that's coming in (Citrangequats root readily BTW) thereby shaving 42" of height off a seedling tree. They have a very upright growth habit and I got that thing to grow a good 16-18" indoors over winter.