Making a gill net:
http://www.aircav.com/survival/asch08/asch08p11.html
One could make a rectangular structure on the sides of the
garden area, shaped like soccer goal posts, anchor it upright
with a cable guy wire and bag of concrete with an eyebolt in it
at the corners, or use those screw-in type pet anchors to anchor
the guy wires, and then run the top suspension lines for the
mesh between the horizontal top poles of the rectangles.
The challenge would be anchoring the bottoms of the mesh
to get that goat fence angle that dcarch showed. Screw-in
anchors would work for that, too, but then you would need
a pair for each row. Maybe a heavy 4x6 post or old railroad
tie at ground level with a series of eyebolts in it for anchoring
lines across the bottoms of the mesh would be cheaper.
They do not need to come all the way to the ground, either.
(The plant is not going to need support until it gets more than
a foot tall.)
One does need a cheap source of lots of parachute chord or
something similarly sized that is pliable enough to tie the
pictured knots with. If you mis-estimate how long your verticals
are, it is easy to just tie on another piece and keep going.
(Vinyl mesh or polyester mesh may be a lot cheaper and not
require the work. Just attach it to the horizontal top and bottom
lines with electrical wire ties or whatever.)
The mesh does not have to be the size that one would see in
a commercial gill net, of course. One could make the spacing
between verticals at the top wider, for example, maybe 8-12
inches.