O.K. I decided to read up on those so called "African" Marigolds, & they are rather a bit day length sensitive, after all.
Seems that even Inca II may also be started as early as February, to get about 9 hrs. of daylight, to help induce earlier flowering, for spring sales.
Otherwise, they may just wait until day length is less than 12 hours, to flower, if sown late ! Or, unless they get a sudden increase in day light exposure level. (Obviously, while being old enough to bloom.)
So, it just may be awhile before I get to see flowers on my Mission Yellow. Playing around with the amount of light exposure levels, can even affect their final height, too.
It would have been nice, if my weather would have been cooperative with my attempt to suddenly increase direct exposure to sunlight. (Being mostly cloudy, lately.)