My citrus trees are thriving in the greenhouse with temps just above freezing.

Ellie:

Your summer weather is perfect for citrus. So I won't want a solid roof overhead in summer. Citrus needs full sunlight to be really productive. Build something that you can close on cold winter nights and heat to 28-32F. That's all that is needed. Otherwise allow full exposure to outside temperatures and sunlight at all other times.

A big problem for me with my potted citrus (after building a greenhouse for them) was that they grew really big. They wear out soil pretty fast so it seems they need repotting about every year and a half. No one wants to help me wrestle these guys out of their pots and into new ones since a lot of them are thorny. I solved the problem somewhat by building what I call "cage pots" using wire mesh (often sold as hardware cloth) and landscape fabric. My pots don't have bottoms so you can't move them around once they are full of media. I estimate they hold 45 gallons of home made growing media (bark chips, gravel, potting soil, etc.). Now the trees can get as big as they want.

To change the soil I can dig down from the top and scoop out sections or I can snip the zip ties that hold the whole thing together and open up the wire mesh and change out the soil. Being tall and made of wire mesh means that I will probably never over water them and cause root rot.

I only say all this because it never occurred to me when I originally got them. Their pots got bigger and bigger over the years. My citrus seem to like gravel-y soils best which tend to weigh a lot making it very difficult to re-pot them as often as they like.

What I'd do in a 16F zone near Redding is plant in the ground under a high tunnel with roll up sides. Put the sides down on cold nights and heat to 32F. During the summer I'd either have it uncovered or use a 30-40% shade cloth. With that system you could grow any citrus that can be grown anywhere in CA.

Thank you so much for the tips. I see that you agree that mostly the issue is the dang cold winter nights. Doesn't seem to bother them in the 112 degree heat, though nothing likes that.

I may just put them outside in the summers and bring in during the winter. This thing should be pretty nice looking, they are even going to finish it on the inside. Much different from my greenhouse.

Ellie