I grow mostly on a trellis, and the spring I had my appendix out and several garden things never got done, I ended up planting my tomatoes a foot apart, but on alternate sides of the trellis. I plant the seedlings probably 6" from the trellis, so putting them on alternate sides did give them more root space than if they'd been planted on the same side of the trellis.

I don't remember how much I pruned, but the plants were too close. They grew well, but it was too crowded for my taste. Well, as they say, it was a learning experience -- and then the Late Blight hit before anything had ripened.

At 18" apart, you'd have to prune to very few stems: probably only two per plant. Planting on alternate sides of the trellis (if that's possible in your situation) would give the roots more room, but would still limit the space for the vines.

Another year, when a relative was ill and I didn't start my own seedlings, I planted far fewer tomatoes than I usually would, and put them on the same side of the trellis at 4' intervals. That spacing worked out well, and I barely pruned at all.

Trellis as in a cattle panel? I have read that some have used 18" IF you do extensive pruning to only 1 or 2 main stems. Otherwise 2' spacing seems to be the minimum recommendation. For me, with indeterminate varieties, that would seem to still require pruning. I prefer 3' spacing.

So how much pruning do you prefer to do?

Dave

Well, other than nipping suckers I don't normally do much pruning. I guess I'll keep it to 3' spacing and maybe have a May seedling tomato sale or give-away!! Plenty more in my garden--corn, beans, eggplants, zucchini, cucumber figs, pomegranate etc.I'm keeping busy this year!

other than nipping suckers I don't normally do much pruning.

Just to be clear....

When I wrote, "At 18" apart, you'd have to prune to very few stems: probably only two per plant," I meant that you would be pruning all the suckers except one: so you'd be left with the main stem and one sucker (a total of two stems).

Indeterminates have a main stem and branches. All the branches are what are called "suckers." [This is not always apparent after the branches have grown a bit, but if you watch carefully as the plant grows, you will see that all the branches begin as "suckers" growing in the "armpit" between the main stem and the petiole (or stem) of a compound leaf. Both the main stem and the suckers have the same growth pattern of three compound leaves followed by a flower truss, repeated until frost.]

If you want to prune all the suckers -- leaving only the main stem -- 18" spacing should be fine. I was raised to remove all suckers, and used to plant tomatoes that close before I realized I'd get much more fruit if I kept a sucker or two. (Now I leave all the suckers I have room for: which is usually everything except the ones right at the ground.) Another reason not to prune so heavily is to have more leaves to shade the fruit and prevent sun-scald.

I plant 18 inches or so. By summer's end I have a hedge of tomato plants that I have to dig through to get fruit. I do this because I have limited space and want to grow many varieties. The plants seem to do good, but I have not had problems with blight or other bad diseases. I do suspect however that I have lower production.

You mentioned that you know that tomatoes root to the side.
Did you realize they can send roots over three feet to all sides?

Here's a link to a fascinating article I got from Carolyn
years ago that talks about extensive studies of tomatoes.

Here is a link that might be useful: Tomato root development

Do any of you have pictures of the trellises/spacing?