The ubiquitous pelargonium, the annual geranium, is a plant that has been grown for decades. The cultivars of today, though are not the boring plants your grandmother had in the 60's. The plant breeders have worked hard to improve plant habits, flower colour, duration and size. There are some pretty impressive plants in this lowly pelargonium. Best flower production is with lots of light, pelargonium tolerates morning sun spots to blazing hot all day sun. The only downside might be the need to pause as you stroll about your beautiful garden, lean over and snap off the flower that is spent. That will ensure more flowers will come (oh, that and sunny days, of course).
Sun, all day sun, part sun (how amazing is that?)