I do this in my greenhouse for tomatoes during the winter and it works fine--but I don't have to worry about wind catching a wall of tomato plants.

Be sure the string is sturdy enough and the posts are secure. From the picture there seems to be some sag already. That would concern me.

If it starts looking like it's not working as well as you like, you might consider supplementing it with a Florida Weave. Maybe you won't need to, just a thought. Here's a video that may explain it better: http://www.youtube.com/watch?v=SRohHQ7mMBw

It is the typical greenhouse arrangement. I used to do it outside as well, but with two strings per plant - the two-leader system. I gave it up for the lazier 5-foot high cages. I might take it up again this year, though, as I happen to have a bunch of wire and posts on hand.

A good friend does a similar thing with his tomatoes, all of them, outdoors. He has a rigid horizontal bar atop the trellis at about 4 feet from the ground (you could use a long sapling). He pinches the tomatoes to a single leader to wind up a string, but once the plants hit the crossbar he stops pruning and lets them rip. He's a great gardener, wouldn't keep doing it if it didn't work well.

This system depends on choosing one or two main branchs and removing all the suckers and continuing to wrap the twine as they grow up

you Do have too much sag in your wire. Consider angled guy wire off the posts with a small turnbuckle which you will tighten as the load increases

REMOVE THE SUCKERS!

I have done this for years. Your support needs to be sturdy. The verticals should be sturdy and especially the horizontal. For 20 plants I use 4x4 as my posts and a metal electrical conduit for the middle horizontal. Make sure you remove the suckers, or it will not work. check out youtube for "stringing tomatoes" and pruning suckers. This system works wonderfully if you do it correctly.

for those that have done this before... how often do you twist the line around the plant.
In my last picture above, I was concerned I might have wrapped around the plant too much.

I don't think that you can wrap it too many times, but you really only need about half of what you have. I noticed your t post could be driven further into the ground...that might help your "sag" which will only get worse as the plants set fruit.

I agree with lonmower. You aren't over doing the wrapping, but it's not really necessary.

I also think I'd put some guy wires on those green, vertical poles or put some sort of rigid, horizontal board between them to keep them from sagging (5 mater plants can easily produce >50lbs of vines n fruit)

I do have turnbuckles on each of the guide wires (actually a clothesline). but I am already thinking of buying 8' long 2"x4"'s as replacements. I just didn't realize how sturdy this setup needed to be.

The T post are sunk as deep as I could get them using a hammer. I had planned to borrow my neighbors T-post driver, but he was out of town and I needed to get something up asap.

I had read a couple of different "how to" articles and kind of mix-n-mashed some different styles.

stepladder and a sledge will drive them.

I use a 5x10 piece of concrete reinforcement wire for a cage. roll it and loop the ends on itself to make a large cage 5' high. The wide diameter give a lot of room for an unpruned plant and generally doesn't blow over, but a couple 2x4 stakes tied off at the bottom will secure it for sure.

If you want to go back to cages you can make your own using pig fence. You cut them about 12 foot long and cut the bottom wire off so they can be pushed into the ground. The extended wires are just folded around the other so all you need is wire cutters. After the season is over if you need to store them you can just unhook them and lay them out flat to save space.

12' long sections? sounds huge. how big a diameter is that... 4'?

I had heard people saying to use cattle panels cut to 4'x4' lengths and rolling them. that should make a diameter of just over 1'. (I'm probably doing my math wrong) The cheapo cages at box stores are probably just under 1' diameter (and about 3' tall if your lucky).

I would prefer to go back to cages... I was planning on slowly buying panels and making cages so that next year i would have cages.

I currently have 15 plants and was looking for an inexpensive way to control my tomatoes.

this video looks interesting... I wouldn't making 15 of these.

Making KIller Tomato Cages.
http://www.youtube.com/watch?v=MWsA80jfIyc

scotty

These are the Guy wires I was referring to. Tent strings, etc.

Here's another idea for giving you some more support to your branches. Run some horizontal strings between the poles and use a stick to spread them apart. These would also need Guy wires (or a rigid joist)

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And I guess you might call my horizontal board idea a joist. Sorta like this:

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Stepladder & hammer will work, but get someone to hold the ladder. I have stood on a tailgate of a truck too.
The weave has been use in N.C. for 30 years, I even saw a small garden with summer squash in the weave, standing vertical.
I plant running beans in the same way as the above photo.

I can't stop researching this stuff.... I have more and more ideas to build! Posted lateste link I discovered below. his electrical conduit trellis aren't pretty but very functional

@tn_gardening - I like the last picture in your post! i'm assuming that's your garden. It's functional, sturdy and very nice looking.

I had no idea I could use a true trellis design rather than the vericl string method. I already made a string trellis for cucumbers.

My latest cucumber trellis, has 6" legs that slide into sleaves on back of raised bed, so i can move it each year.
{{gwi:36701}}

Here is a link that might be useful: future farms trellising pumpkins

Twine has not worked well for me as the vertical line, particularly if a good, heavy rain hits late in season with full vines. I doubt twine would come close to holding the horizontal. I use/re-use a heavy trellis wire for my verticals. I use twine to tie the vine to the vertical. I tie a half-hitch around the vertical, then a square knot loosely about the vine. There's a youtube video showing this...