Annuals--you would have to experiment as your conditions are difficult re light. The shade plants the would do well with only a few hours of sun usually don't like hot PM sun. The plants that like hot PM sun won't take kindly to those long hours of deep shade; you no doubt get your share of cloudy, rainy days too during your Quebec summers, so it is not as if you can count on continuous sunny days during those 4 afternoon hours.

There are still many annuals to choose from. You might try snapdragons, nicotianas, branching sunflowers, plume celosia, coleus(most of the new cultivars are sun tolerant),fuchia 'Gartenmeister',larkspur, browalia, tall ageratums, or pansies. I have grown all of these in similar situations and had quite a bit of success. All but the coleus and probably the browalia are good for cutting.

Thanks Ginger, I will try most of what you have suggested!!

Try a lot of perennials like bearded iris and coneflowers.