Fortunately, some are fairly shadetolerant, too, Included in this group are browallia, coleus, exacum, lobelia, pansy, sultana, wax begonia, and wishbone flower. Very few of these, however, will thrive in continuous dense shade. Still other kinds bloom satisfactorily in partial sunlight, or even light shade, but not as well as in full sunlight. Aside from adequate light and choosing kinds adapted to your climate, annuals are rather undemanding in their general requirements. Most soils, even poor ones, can be modified or improved to grow fine flowers.
Good drainage is essential.
In many areas, natural rainfall won't be adequate and should be supplemented by watering, particularly during drought periods. And several light applications of fertilizer are usually needed. Raising good flowering annuals is becoming more of a challenge because our environment is changing, often for the worse. The resulting stresses have a definite effect upon the plants we grow. Crowded conditions exist, especially in urban areas, with serious pollution of the air, water, and even soil.