In all but the coldest climates (where temperatures dip below five degrees below zero Fahrenheit), pansies can be planted in fall. They grow best in moist, well-drained soil and benefit from a light application of balanced fertilizer (10-10-10) and a light application of mulch for winter protection.
Fall-planted pansies begin blooming soon after planting and continue through spring. When freezing temperatures arrive, they often curl up and freeze solid, but will perk up when warmer temperatures return. Pansies bloom best in late winter and spring, then poop out when the heat of early summer arrives.
If you miss fall planting, or if your winters are extreme, plant pansies in early spring, as soon as the ground thaws. Water pansies during dry spells to prepare them for freezing weather. The smaller Johnny-jump-up (Viola tricolor) can be planted in the same way as the larger pansy (Viola wittrockiana).