I planted a sunflower two months ago for a school experiment, and only one of the sunflowers bloomed the other day -- it was the plant that was planted together in a plot with Vietnam Rose (Portulaca grandiflora). As for the other others that were planted alone, they haven't bloomed, but there are 2-5 sunflowers that are soon to bloom in each of the single plants, while only a single flower bloomed in that which was planted with the rose.
I'm wondering could the sunflower with the rose have bloomed early because of the competitive environment? Or could it have been pure coincidence?