On page 39 of the Richter Herb catalogue the claim is made that this Mexican Marigold will fight weeds?
Has anyone grown it and what do you think of the claims?
It is tempting!

Oh my gosh, it it could really be true! I may have to experiment this year.

It has been said that this plant can be an effective weed, and nematode control when used as a cover crop. Having said that though, there are some agencies that do list this as a noxious/invasive weed. As for "fighting" weeds…I'd be interested in knowing how they came about this assumption…Maybe it would "take over" an area ( thus being noxious/invasive on it's own ) and crowd out 'other' weeds. Maybe ones persons 'weeds' is another persons 'ground cover'.

I was thinking that perhaps it gives off some root exudate which is toxic to some other plants?
I am skeptical , but might try it once.

According to the Horizon Herbs catalogue:
it gives off thiohene by its roots.

From what I can find, the Marigolds would have to be planted as a cover crop to do much good against nematodes, and planted densely to prevent weeds. So it does not sound practical as a method to be used in the garden, except in places where they could be grown as a cover crop when not growing other things.
I have tried planting regular Marigolds for insect prevention, just spaced out among my tomatoes etc. I could never tell they did any good, however, I still plant them among my vegetables and other plants, just because I like Marigolds. Not that familiar with the Mexican Marigolds, I did see it was listed as medicinal weed.

Yes, I am going with the ordinary garden variety of marigolds.
I do like the flowers on the other marigold which is called Mexican marigold also.
Marigold Cempitrichi? It has ridges on the end of the petals and is a more single flower.