bbum@Flickr, aka Bill from San Jose, California, contributed today's photograph (original image | BPotD Flickr Group Pool). Thanks again, Bill – I appreciate the contribution to this month's occasional theme of orange and green (and sometimes white) on BPotD.
I'm not able to tell from this image or Bill's other photographs of this marigold field as to whether these are a cultivar of Tagetes patula or Tagetes erecta, but perhaps someone more expert will make a suggestion. In either case, though, these bright plants have a common name in Mexico that is anything but bright: la flor de la muerte, which translates to “the flower of death” (according to Allan Armitage in his “Manual of Annuals, Biennials and Half-Hardy Perennials”). Unfortunately, Dr. Armitage does not explain the reason for that moniker. Speaking of names, I should also note that the common name “marigold” outside of North America often refers to members of the genus Calendula.
Dr. Armitage notes that the roots of some species produce allelopathic compounds, which can suppress certain weeds. For this reason, and the fact that they can also deter some unwanted insects, Tagetes are sometimes used in companion planting.
Botany resource link: Flora brasiliensis is a project to first digitize the 1840-1906 textual work containing nearly 23000 Brazilian species and then update the information. The site can be a little difficult to navigate, but viewing some of the line drawings can be very rewarding (sorry, I'm not able to link to any images directly).