Step 1: Go to any camera processing shop and get as many used disposable cameras as you can. (100 should do the trick
)
Step 2: take them apart keeping the chips in tact.
step 3: snip off the caps and hook them up in parallel
step 4: hook the charge circuit (depending on the brand it will vary) and put them in parallel
step 5: hook up a fuck load of AA batteries in parallel so you get alot of juice but low voltage (do not exceed 3volts so to banks in series would give 3volts)
step 6: put batteries to a switch to the charge circuit to the caps
step 7: put some mesh around the seedlings but insulate it from the ground.
step 8: hook up your batt/charger/caps to said mesh
step 9: DON"T FUCKING TOUCH THE MESH NOW
400volts at only 1 farad caines like a mofo.
How do i know this?.....experimented with homemade tazer and coil guns which essentially use the same principle as an electric fence. A SINGLE fully charged disposable camera will leave a burn mark on your skin. 5 will leave a substatinal burn mark. 10 starts to cause perm scaring.
What does this have to do with your problem?....any fucker who is dumb enough to touch the mesh will get a nice surprise
Best part is its essentially free to make this. Minus the couple $$ for the switch and some wire and solder.
EDIT: Make sure you hook your switch up BEFORE the charge circuit. Failing to do so and as a result using a switch AFTER the charge will result in a fucked switch. Most switches cant handle the voltage and therefore fuse together. If you want to have a switch AFTER the charge bank you would need to use a relay as they the only things that would take it.