Yes, that's exactly what you should do. Make sure you're using an "in use" cover that allows it to remain waterproof while the cord is plugged in.

That's what I'd do. Keep in mind that you need to use PVC conduit where it runs underground, and the PVC cannot be "exposed to physical damage." This means you need to run EMT above ground, anyplace where you can see it. inside the wall in the garage however, you can use PVC because it's not exposed to physical damage. Alternately, you could run type UF romex, rated for direct burial. But same rules apply, it cannot be exposed to physical damage. so it can be directly buried, but you need to use EMT where it comes above the ground. It would need to be buried I think 18-20 inches, and you need to have some additional barrier to protect the cable. some cheap cedar fence slats buried on top of it would work great.

Some things to know about conduit: EMT and PVC alike need to be supported within 3' of a box, and every 10' thereafter. You may NOT exceed 360 degrees of total bends between boxes. if you do you'll have a hell of a time pulling the wires. Lastly, you can't pull romex in a conduit. you need to use type THHN or THWN copper.
Hope this helps. I can tell you the articles in the NEC if you'd like.
One last thing, don't waste your money on expensive pre bent PVC fittings, just heat a piece of straight PVC with a propane torch or something hot. (go slowly and don't burn it!) it'll look nicer and be all around better quality.

Most of the above post is wrong.

There's no reason it has to be PVC, though that's what I'd use. There are lots of metal conduits that are permitted or can be listed for underground burial. Yes, you can't use EMT for that, but that's not the only metal conduit out there.

Sched 80 PVC can be used for protection from physical damage.

There's no earthly good reason to use EMT at all here. The support requirements for PVC aren't "every 10 feet" it depends on the conduit size (and sometimes other issues). That is the requirement for EMT.

UF is not "romex" but it is permitted for direct burial. The problem is it still needs to be sleeved when it comes out of the ground and you can't USE EMT for this (sched 80 PVC would be OK). Yes you should not be pulling cable in the conduit (except when necessary for the physical damage protection).

You can't use THHN for this at all either (although you typically will not find THHN that's not also rated THWN).

Speed freak is right about the number of bends. Not only does it make things difficult, it's not permitted by the code.

Using a torch to bend PVC is also illegal. It requires the equipment to be identified for this use and to make sure the inside diameter isn't reduced.

Cedar shakes are not a way of protecting ANYTHING. The only protection that reduces the requirement is 2" of concrete on TOP.

In the general case, cable (UF or whatever) has to be 24" down, but in a special case that probably applies here, if you have a GFCI protection on it and it's a 20A or less circuit, you are allowed to only go down 12.

If you use PVC you have to go to 18". Other conduits have requirements for between 6-18 depending.

If you go for rigid or intermediate metallic you only need to have 6 inches of cover.

That alone make it a decent option many times.

If you go for rigid or intermediate metallic you only need to have 6 inches of cover.

That's mighty shallow. Even 12" is close enough to the surface that it can get in the way when the homeower is digging a garden. But at least the raceway will protect it, which is not the case with 12" buried, GFI protected UF.

As I see it, the code depth requirement is a minimum. The pros will probably bury it that deep, which is fine. But as the homeowner who might want to dig up that area someday, I prefer to bury at least 18".

There is not a lot that is going to damage rigid or intermediate conduit.

The are about the same as steel water pipe in thickness and strength.

If you hit it with a tiller you are going to damage the tiller and bring it to a very quick halt.

This is the stuff used in explosion proof systems.
Even if a mixture is ignited inside the conduit it will contain any flash and blast.

There is no practical need to put it more than 6 inches in a residential yard setting.

Thanks for all the input. Although all the input was useful, I always hope to get input from "brickeyee". For several years I have read his inputs and he/she seems to have it all together.

Anyway, I ended up using PVC (grey stuff) and buried it 18/20 inches. All of the above ground is metal. I have installed a GFCI in a waterproof box with an "in-use" waterproof cover.

Presumably the metal is either not in contact with the earth or is rated for it. Speedfreaks suggestion of using EMT for that is outright illegal and dangerous.

While I agree with brick that rigid should be fine as far as protection from tillers and digging, my wife would be way pissed if I put things at 6" through places in the yard she is landscaping (which is all of it).

"wife would be way pissed if I put things at 6" through places in the yard she is landscaping (which is all of it). "

She is going to be even more pissed at the damage from digging 16-18-24 inches deep, even with a ditch witch.