Growing tomatoes: the string trellis experiment

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Every year, I plant more tomatoes than I have room for. And every year, my tomato plants get hit with mildew. Crammed together, the tomato plants block each others’ access to sunlight and air, providing perfect conditions for pests and diseases, and reducing the quality and quantity of the fruit.

To make things worse, all the crowding makes it even more likely that I’ll forget to prune the suckers. Pretty soon, that whole area of the yard has turned into one huge impenetrable tomato thicket. Until the mildew hits and then the whole thing turns brown and dies.

Which brings us to the new garden structure and the tomato string trellis experiment.

Tomato support structure made from EMT conduit

The concept is this: instead of growing your indeterminate tomatoes in cages or tying them to stakes, you prune each plant to a single vine and train it vertically, up a rope.

Training the tomatoes to grow vertically means all the plants get more sunlight, even though they’re planted fairly close together. Pruning improves airflow, which keeps the leaves dry and mildew-free, and makes it easy to keep an eye on suckers and pests. And without the sprawling side growth, the plant can focus its energy into the fruit.

Red and green Stupice tomatoes and rosemary growing

Traditional tomato cage

Tomato (Solanum lycopersicum) with green fruit, climbing a rope support

Tomatoes growing on a string trellis

A friend swears by this method, and last year he harvested hundreds of pounds of tomatoes. Of course, he’s much more responsible about his gardening than I am, and actually pays attention to growing seasons and reasonable plant spacing. Still, I figured I’d try the rope method, since I’d run out of regular tomato cages anyway.

My friend grows his tomatoes in a hoop house, which provides a convenient structure from which to hang all those long ropes for the tomatoes to climb. He suggested I repurpose up an old swingset or build a basic A-frame with a 2×4 or pole across the top. If you wanted something less three-dimensional, you could certainly just build a flat trellis-style frame and pound the legs into the ground, or bolt them to the side of a very sturdy raised bed.

Technically, I think my final structure is more of a half-assed pergola than a trellis, but it is freestanding, stable, and strong enough to support the weight of the hundreds of pounds of tomatoes that I’m anticipating.

Tomato string trellis made from EMT conduit

I made it out of 3/4″ EMT, the rigid metal tubes that electricians use to protect wiring and everyone else uses as grown-up erector set components. Around here, 3/4″ EMT goes for around $3 or $4 per 10-foot pole. They have nifty tools for bending EMT to perfect angles and curves, and the internet is full of instructions for cheap DIY jigs that do the same thing. Being too lazy to borrow a tool or build a jig, I bent my EMT by hand, wedging the pipes against the fence for resistance. The results were a little uneven, but good enough.

My structure ended up looking a bit like a child’s line drawing of a house. This was less about engineering or aesthetics than about making use of the connectors I already had on hand. Like so many of my project components, I found them here when we bought the house. Apparently they’re actual things that you can buy for making canopy supports and Burning Man shelters out of EMT. If you don’t have any lying around, you can just get the EMT connectors that electricians use, or get creative with plumbing fittings.

Homemade connector bracket for tomato trellis built from EMT conduit

How to train the tomato plants

Once you have something to hang your ropes from, the rest is pretty straightforward. I learned by watching this excellent video, made by the folks at Front Porch Farm: How to string and sucker tomato plants

A few key points:

  • Once a week or so, I twist the tomatoes around the ropes and pinch off any suckers. As the slack gets taken up, I can let out more rope from the reserve loops at the top.
  • Some people use little plastic clips to fasten the vines to the string, but you can just twist the vine around the string, or vice versa.
  • I tied the end of the rope in a loose knot around the base of the plant; other people tie the ends to stakes or the base of their support structure.
  • Pinch off the suckers. These are the little shoots that grow out of the crotch where leaves meet the main stem. If you leave them, they’ll keep growing and branching and it’ll be a mess.
  • Do NOT pinch off the fruit-bearing branches. After a while, these are easy to identify, because they have flowers instead of leaves.
  • Do NOT pinch off the very top of the plant. That’s where new growth happens. If you prune it, the plant stops growing. I did this by accident. Fortunately, the plant keeps putting out new suckers, so I let one of them turn into the new main stem, but that plant is a lot shorter than the rest.

Tomato (Solanum lycopersicum) climbing a rope support
Sungold tomato plant with rope twined around vine