Adapted from Straight-Ahead Organic, by Shepherd Ogden

SIMPLE SOLUTION:  To make your own wire cages for tomatoes, buy concrete reinforcing wire (available from most building supply stores).

• The conventional directions are to cut a six-foot section of the five-foot-wide wire, and bend it around to make a column that surrounds the plant. This should be anchored with a stout stake against wind.
• The Quonset Tomato Trellis Method A better solution, using the same materials, was taught to me by a French seed salesman who visited our garden one summer. Instead of taking the concrete wire and making a column, you cut the wire to any manageable length and then bend it lengthwise, over the rows, in an arch. This way, as the plants grow they will pass up through the mesh and rest on top of it, safely off the ground, but absolutely certain not to blow over.
  -- Whatever kind of wire you use, and however you use it, though, make sure that the mesh is a minimum of five inches square so you can reach through to harvest any fruit growing inside.
  --These wire Quonsets are widely adaptable to a number of smaller crops as well. A five-foot section does an excellent job supporting peppers and eggplants (as well as annuals grown for cut flowers!), and a four-foot section, spanning a row of snap beans, will keep even a full crop of pods up off the ground, thus preventing losses to rot.
  --An added benefit is that you can drape plastic or fabric covers over these makeshift "Quonset" trellises for the first few weeks to encourage early plant growth.
  
• Tall Crop Systems For taller crops, one adaptable system is made from vertical wooden posts with lengths of electrical conduit running horizontally between them. All that is required for this kind of trellis is a collection of electrical conduit sections of convenient length and solid, sharpened 2x2-inch wooden poles—two, four, and eight feet long—that can be strung up with untreated garden twine in various configurations.

HELPFUL HINTS: 

• I use untreated twine so that, once the crop is harvested, I can simply cut down the lines, with the plants still attached, roll up the whole affair, and throw it on the compost pile. Treated twine will not rot as fast, and puts biocides in the compost.
• It is particularly important to stake tomatoes. While many garden centers sell inexpensive conical wire tomato cages, most are way too small for an indeterminate tomato, and any tomato plant that is small enough for them probably doesn’t need the support. You can make better wire cages easily and inexpensively.