toward what purpose???

i would just place them so they were pleasant to the eye.. a little bling in an otherwise boring veg bed ...

im not sure they have any true benefit otherwise ...

but if they make you happy ..... dont let my opinion sway you ...

ken

It is established that marigolds can kill root knot nematodes, which can be an issue for many summer vegetables. Their roots are toxic to nematodes. Of course, that just means that the nematodes that try to eat marigold roots are killed. Doesn't necessarily kill all the others. It is less established, and mostly just rumored, that they repel other insect pests.

Although the benefits of companion plantings tend to be more folklore than fact, marigolds DO provide some benefits. French marigolds in particular can be effective against nematodes, which can be a damaging pest of tomatoes. And marigolds also tend to repel cabbage moths, so planting alongside cabbage family members - cabbage, cauliflower, broccoli, etc., can be helpful.

To look at it a different way, planting your marigolds among the veg is certainly not going to hurt anything. They will attract pollinators and beneficial insects, they are easy to grow and flower a long time, they can be used as a 'trap' crop to attract slugs and snails away from more desirable plantings. And they are edible as well, so not at all a bad choice to include in a veg garden!

I'm in the folklore camp. IME marigolds didn't do a darn thing to repel cabbage moths in the brussels sprouts, even though they were planted right next to them. But they are cheerful to look at and attract beneficials, so I grow them out there anyway. :0)

Only certain varieties of marigolds inhibit the growth of root knot nematodes, and only if they are planted in mass - fill the whole bed with them. https://www.gardenmyths.com/nematodes-marigolds/