How to protect tropical trees? (Webster: house, live, fence)

[Dopo]

In spring, I planted 5 small trees (about 4' tall)
2 date palm trees, 1 mandarin, 1 orange, 1 lemon.
All of them are about 10' away from my back fence that is 6' tall (hopefully that helps to block the wind).

What do I need to do for my plants to survive winters?

[TexasRedneck]

You might protect them a season or two, but long-term chances are you'll lose them. They're tropicals, and as such don't tolerate colder climates. About the only chance you'd have is by building a heatable structure around them that can be erected in the winter. A good calm freeze and you're gonna be in trouble.
Personally, I'd transplant 'em ASAP into movable (very large) containers. My folks did that, kept a number of tropicals alive that way for decades - when a freeze was immenent they'd move the plants into the barn with a heater.

[Proffer]

How do kumquat trees and magnolia trees survive in SA winters? I think that sago palms seem to survive, too. Are they less tropical or something?

[Bo]

Bob Webster says that you can make tender plants more cold tolerant by regularly spraying their foliage with a diluted solution of liquid seaweed. It toughens the leaves. This needs to be done for weeks before the cold weather hits.

[Mom2Feebs]

Lemon trees can be protected easily. Wrap the base with a sheet, then cover plant itself with a tarp or sheet. If you can put a light on it (not LED) that will help, but it isn't necessary to keep from killing it. Expect damage, not necessarily death though, if we go below 25 for too long like we did last year.

We lost one tropical last year: a beautiful hibiscus that had grown into a tree. It got down into the teens at our house and was below 32*F for more than a few hours.

[RGJ]

I've seen where people have placed those portable propane patio heaters. Depending on the size of the tree and the wind factor, it seemed to work for them. But it's an expensive proposition.

[Dopo]

I'm seriously thinking about building something like this but a much simpler removable version for the 3 tropical trees.
They are only about 7' apart... should be a total of about 15'-20' long.

If necessary, I'll run electrical power (underground) and install a couple of lights next to each one of them. (Not likely, but a possibility).

[HillCountryHotRodMan]

Hey Dopo do you have the link to the website where you got that photo from? That looks like a pretty good idea.

[Dopo]

Just do a google image search for "mini greenhouse"

I really like this one that was done with PVC piping (it's actually for tomatoes)

I'm seriously thinking about doing this last one.
FYI, I would just put some rebar in the ground so I can easily put it in and take it off.

[HillCountryHotRodMan]

I need something to fend off the leaf footed bugs from my tomatoes next year and that first picture looks like the answer.