You can do what Marc said, but you can go to Home Depot or any place like it and buy a bundle of stakes that already have the v-point cut on it (their about 2-3' long). They are basically the same as what is used in the silt fences. Anyways, pre-drill a hole in the center about an inch from the top. I can't recall the diameter of the wire, but you buy it by the roll and can usually find it at farm supply, retail store, co-op, etc. Like marc said, electrical fence wire is about the same diameter. I call it "Bailing wire" as it is similar to what they used to use for straw bales before string. Anyways... you are going to use 3 stakes in a triangular pattern with the tree being the center. On a Maple or normal tree, you would go to the first set of branches and place your hoses around the collar, but in your case try to find a spot about 1/2 way up on the smaller trees and about 5' on the taller ones. Using black soaker hoses is sometimes less noticable, but it's still the same principle. Once you run one wire thru the hose, take both ends and go to the stake and wrap it around it making sure it is tied up tight, like you would your loaf of bread. (2-3 times around and twisted together) Your stake will be placed at the edge of your tree ring or in your case the dripline. This will essentially be 10-12' of wire since it is wrapped up to the base and back to the stake. You may want to place it before you cut it, just to make sure. Once you hammer the stake in the ground (at a 45 degree angle towards the center of the tree), you can take another stake or a screwdriver, your hammer, pruner... whatever, and place it between the wires. Then start turning it like you are raising or lowering your trailer jack(over and under). Once it starts to twist, this will increase the tension on the wire.
It's really hard to describe the process via typing... and I am sure it is hard to understand without seeing. I will try to find a site that it is used on and take a picture either post it or email it to you..... will that help? By the way, I am not saying my way is the best procedure, I have just seen it done time and time again. Marc said the same thing , and he sounds like he came from the same gang.