If you set up a place for them to climb AWAY from the tomatoes, you will be OK I think, though competition may reduce some of the tomato's potential harvest.
First thing to do is push tall poles in the ground next to the beans so they will climb the poles rather than the tomatoes or the tomato's supports. Keep the beans away by checking every day and unwrapping the beans and re-wrapping around where you want them to go.
Then you can secure horizontal support -- a pole or wire connecting the top of the poles. (I use zip ties to secure poles)
- I'm saying poles because I like using 7 foot 3/4" - 7/8" bamboo -- you could buy vinyl coated metal tube or Fiberglas ones (these skinny rods/poles are usually sold as posts for net deer fencing I believe)
Another way to do this is to set up sturdy posts and an upper horizontal first, then tie strings from the upper horizontal -- use earth staples or just a stick and tie down the strings right next to the beans -- the beauty of this system is that the strings don't have to be plumb. They will climb the strings.
Set up the trellis so once the beans climb to the top and sideways, they won't shade the rest of the garden.
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