Here’s an example: Plants in the bean family does not normally thrive if planted near vegetables like onions, leeks, garlic and scallions. These veggies inhibit the growth of beans.
Mindi suggests not planting beans near marigolds too. (I’ve read elsewhere that some marigolds can act as a herbicide to certain bean plants). I’ve found that beans do well when planted with carrots, cabbage, celery,and potatoes.
This is a helpful article when planning your garden. Click on the Companion Planting or What NOT To Plant Together link below to read the complete article.
Mindi has a second related post that might interest you: Companion Planting Part 2 – Don’t Plant These Together Too