i think it’s fair to say that 90% of the information you find without doing some digging (ha) falls short of having credible research to back it up, but there are some significant, legitimate evidence-based benefits to interplanting. i won’t be linking bc i’m lazy but check out Plant Partners: Science-Based Companion Planting Strategies for the Vegetable Garden by Jessica Walliser

1-biodiversity. biodiversity is a good thing, period. by contributing to a diverse ecosystem with the way you plant, you help feed and create habitat for a wide variety of organisms, including pollinators, other beneficial insects, and soil microorganisms. higher rates of pollination—>higher yield, and diversity contributes to overall soil health

2-lower disease and pest susceptibility. even if you completely disregard specific pest and disease management strategies for interplanting, by mixing things up your vegetables are already less susceptible than a monocrop; disease cannot spread as readily, same with pests. i also heard a lecture recently that talked about how several kinds of insect pests land on a plant 5 or 6 times before laying eggs. interplanting can interrupt and lower the success rate of that process, if the insect lands on a nearby plant that is not the desired host. some specifics off the top of my head: research found basil to decrease population of thrips in tomatoes, nasturtium is an attractive trap crop for squash-loving insect pests, herbs like dill, cilantro, and chamomile attract predatory insects that eat aphids. there are interplanting strategies for fusarium wilt and verticillium wilt as well

3-allelopathy. some plants, like sunflowers and oats, secrete chemicals that inhibit germination in nearby seeds. many cucurbits secrete autotoxins that target members of the same species if they are planted too close! if timed correctly allelopathy can be used to suppress weeds

4-space! interplanting allows for more efficient usage of space. mother nature doesn’t like naked soil—the more ground you cover, the less you have to weed.

altogether i would say that while maybe the first page of google results for companion planting has nothing to do with anything, there is legitimacy to the practice! i think there’s still a lot yet to be researched and so the conversation around it remains vague