Breeders crossed the American and French Marigolds. What they came up with was a sterile triploid or mule marigold. I often feel sorry for the mule marigold, as it cannot produce any offspring. All it can do is bloom and bloom some more. Of course, this is good news for the homeowner who does not have to remove the faded flowers.
Marigolds can take a lot of heat.
The only problem that you may encounter with this species is spider mites. These creatures quickly suck all the sap out of the foliage and bloom. Wash down the plants occasionally or spray with Malathion. This summer-loving plant takes a lot of heat. Breeders have had a field day with this plant.