Don't subscribe to any of the old wives tales - especially if you are talking about the so-called "companion planting" claims - so my only 'concerns' would be that they have very different nutrient needs.

Beans don't need, nor tolerate, all the nutrients - especially nitrogen - that tomatoes, or even cucumbers, require. I'd suggest you put the cukes with the tomatoes and the beans separately.

When doing intensive planting it is especially important to match both nutrient and water needs for the plants used.

Dave

I frequently plant pole-beans near tomatoes, whether intentionally or unintentionally, and IME it is true that pole-beans tend to get all over tomatoes. The result usually is that the tomato production is reduced at best or nearly eliminated at worst.

When you say you have two 8' spaces, do you mean two 8'x8' spaces, and are they right next to each other? And where are the built-in trellises in relation to the space? I'm asking because it would be ideal if the trellises were on one side of each bed, then you could plant the beans and cucumbers along the trellises and the tomatoes on the other side. That would keep the tomatoes from getting snarled with the climbers.

Dave --

Thanks for the thoughts -- definitely something I didn't think about. Maybe that means I'm not fertilizing my tomatoes enough because I usually just amend with compost in the beginning of the season and water with liquid kelp/seaweed every couple of weeks. I'll look into that and try to take that into consideration in the plan.

annew --

I have two 3'x8' with an industrial strength trellis along the back edge of the bed (spanning those 8' squares). I trellis my tomatoes since they are usually IND -- it keeps things neat and tidy -- hence why I'd like to plant all three of these vegetables next to the trellis.

Thanks for the feedback.

It's also important that your pole beans do not shade the other plants like the tomatoes and cucumbers. If you grow the pole beans on the north end of your garden area, then they will not shade any of the other low growing crops. I have never had any adverse effects from growing tomatoes with beans, as long as you can fertilize and water differently, as needed.

Here is a link that might be useful: The Biodynamic French Intensive System

Have you grown pole beans before? They can run like crazy and get super-thick. of course you could always prune them back if they start covering the tom plants.

My mom plants bush beans in front of her tomatoes (with marigolds around the edge) and never has had any problem. Just make sure the beans are planted on the sunny side :)

The thing to remember with most companion planting do's and dont's is that very few, if any, have actually been scientifically tested. The evidence is purely anecdotal and is at worst based on old wives tales at best, peoples experience in their own garden. Not to say that people are wrong, or that they didn't experience what they did, but keep in mind that what works for them may not always work for you and vice versa.

That is not to say companion planting is all hogwash and should be tossed, I still follow it as a general guideline when planning my garden. What they used to tell me in the Army though was "a guideline is not a regulation" and so I look at it that way with my garden.

The only real problem I could foresee with planting beans cucumbers and tomatoes is that beans and cucumbers are viney climbers and may decide to use your tomato as a trellis and possibly choking it out. I have grown cucumbers and tomatoes together before and neither suffered any bad effects from it. The cukes did sort of start climbing on the tomatoes but not enough to really effect the tomato in any way. The only problem I have had with it is the tomato being so big I couldn't see all the cucumbers hiding in there!

I say, all things being equal, go ahead and try it. If it doesn't work then you have learned that, if it does, then you'll be glad you shucked Wikipedia's advice and tried something new.