Trellises are an integral part of garden equipment. Many crops are not only more productive, but more resistant to disease when grown on supports, whether it’s something as simple as a stake in the ground, or expensive store-bought pipe-and-mesh trellises for trailing and climbing plants. Note the interplanting of spinach between the pea trellises above; we’re just about ready to “string” this trellis, and the spinach will benefit from the shade of the peas as warm weather approaches.
While many garden centers sell inexpensive conical wire cages. you can make better wire cages from concrete reinforcing wire (available from most building supply stores). The conventional way is 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 (we use a six foot piece of reinforcing bar) against wind. Then sow pole beans around the perimeter, or set a couple of cucumber or melon plants just inside; a single indeterminate tomato plant in the center will fill the entire cage in short order.
For lower growing plants better solution, using the same materials, was taught me by a French seed salesman who visited our garden one summer to see the vegetable trial plantings (for which he had supplied the seed). 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. 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. 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 far 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. The plants grow up through the support, eventually all but hiding it, and—with its help—hold their stems straight (in the case of cutflowers) and helping keep field mice, moles, and other crawling pests from bothering the harvest.
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 2×2 inch wooden poles—two, four, and eight feet long—that can be strung up with untreated garden twine in various configurations. You can also use green metal fence posts from the hardware or farm supply store, bend the ends of the conduit 90° and then fasten the conduit to the stakes with a hose clamp.
Electrical conduit is available in ten-foot lengths at hardware and building supply stores and is a relatively inexpensive material for trellises. In my own garden I make trellises of two lengths: five and ten feet. This allows efficient use of the conduit, given the size of our beds, but there are innumerable other possibilities that might be more applicable to your own garden. The conduit can be cut with a tube cutter or hacksaw. I buy the 3/4-inch-diameter size, flatten three inches or so at each end with a hammer, and then drill a 1/4-inch hole an inch in from the end.
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. And if you choose to use treated wood, keep it to a minimum. When you buy treated wood, or treat it yourself—even by painting—you not only expose yourself to the chemicals involved, but you create demand for them, which means pollution being created somewhere else, in the place where they are manufactured. Use treated wood only where absolutely necessary, use as little as possible, and make sure it lasts as long as possible.
To erect this kind of trellis is simple. Set the first stake and gently pound it into the ground to a depth of eighteen inches or so. Lay the conduit next to it, running along the row; its length will determine the spot to erect the second post. Set the second post so that the top is generally level with the first, then lay up the conduit so that the flattened ends are on top of the stakes and screw down through the holes into the top of the stakes. We use black drywall screws, which go in easily and hold well. the weakness of this system is that it is not suited to windy locations unless the end posts are very well anchored. This is because wind blowing at an angle to the run of the trellis can twist it around; with diagonal braces at the top it may resist that, but it will still be prone to blowing over in a storm.
Of all the systems I tried over the years, some store-bought and some homemade, I become convinced that the cheapest, most adaptable, least troublesome to store, and easiest to maintain is bamboo, and I now use it almost exclusively for our tall crops. By using only four sizes of canes (four-, six-, eight-, and twelve-foot lengths) we are, nonetheless, able to construct equivalents to any of the post and bar trellises described above, precisely sized to our beds. Using a teepee system, the resulting trellises are much more wind-resistant as well.
The basic unit consists of two sets of four 8-foot canes and one 12-footer. Set the first four canes 2 feet apart each way in a square at one end of a 12-foot row (any lesser length will work just as well, using a shorter top cane), and repeat this at the other end of the row. Then cinch the tops of the canes together with untreated twine 8 to 12 inches down from the top to make two four-legged teepees, lay the 12-foot cane across the two tops, and cinch it down. This makes a very stable, wind-resistant structure functionally similar to the pole-and-conduit trellis described earlier, but capable of handling two rows of plants. You can also use bungee cords or very large cable ties to bind the four canes together
Regardless of which materials and method you use to build the trellis, you should rig it with untreated twine. The first step is to tie a taut line from upright to upright an inch or so off the ground. (Make sure it doesn’t touch the ground, or it will rot prematurely.)
From this point the method of rigging will differ according to the crop being grown. For tomatoes and large vining crops like cucumbers, melons or pole beans, run a single line down from the top bar, cinch it to the bottom cross line, then tie it around the base of the plant with an oversized non-slip knot. (A slip knot will tighten up over the course of the season and eventually strangle the plant.) Tomatoes need to have slack left in the line, but for the other crops the vertical lines can be reasonably taut. If the plant climbs by tendrils, or sends out a lot of lateral branches, horizontal lines can be run every foot or so up the trellis to provide extra support. With the bamboo trellis you will end up with sets of twine, both angling toward a common top bar.
In sum, plants that grow by twining, or can be manually twined (like tomatoes) need mostly vertical lines, while those like peas and cucumbers, which climb by gripping with tendrils, need more horizontal members.