Choosing flowers in season is as simple as seeing what's for sale at garden centers at each time of the year. It's also important to know what growing zone you live in, and what those conditions are for each season. Some areas stay warmer longer, some become cooler more quickly in the fall. Winter in most places is not considered a planting period, unless it is mild, as in southern climates. But spring, summer and fall can be planting times for many different kinds of flowers in most areas.
Choose flowers for spring planting that can take a little cool or cold weather for short periods without being much affected. These include pansy, cosmos, viola, dianthus, poppy, campanula, calendula, snapdragon, forget-me-not, primrose, sweet pea, larkspur, chrysanthemum, candytuft and ornamental kale--a type of cabbage with colorful purple, white and green leaves. There are others, depending on the spring conditions where you live. Northern climates, which stay colder longer, may restrict spring planting to particularly hardy plants, such as pansy, but remember that an unexpected cold snap in any growing zone can damage any plants that have begun growing. Still, the plants may survive if they have established roots and then put up new shoots and flowers as the weather warms consistently. Spring planting months include March, April and May.
Plant summer flowers almost any time during the warm growing months in your zone, usually from June through August. There are many flowers to choose from, such as: ageratum, sunflower, impatiens, zinnia, marigold, portulaca, black-eyed Susan, strawflower, blanket flower, lobelia, petunia, phlox, salvia, verbena, morning glory, heliotrope, aster, gerbera daisy, nicotiana, vinca and geranium. Those are just a few of the warm season flowers for most areas. Remember that summer planting requires deep and frequent watering to help plants establish roots and to keep them from drying out in hot conditions. Mulching around new transplants helps retain soil moisture and also keeps down weeds. You might have to water new plantings daily during the hottest periods, and keep a close eye on the soil moisture in containers, which can dry out very quickly. Summer lasts longer in southern climates and ends sooner in northern ones.
Select flowers for fall planting that can take warm to cool conditions, much the same as you would in the spring season, although the conditions are the reverse: warm days turning to cool ones. The most popular fall plantings include chrysanthemum, aster, pansy, viola, dianthus, Chinese forget-me-not, primrose, stock, sweet pea, poppy, African daisy and ornamental kale. Bunches of mums are especially dramatic in the fall landscape, along with purple-leaved ornamental kale. Some fall plantings may survive through the winter in southern climates. Those plants include pansy and primrose, which can also withstand cool to cold weather for several weeks. Many of these fall plants may re-seed themselves as they die in late fall, and surprise you with new sprouts in the spring. The fall planting months are September, October and November.