Pansies and violas (similar plants with smaller, more numerous flowers) are one of the standards that appear in nurseries in the fall besides the mums and winter kale and, in many places, will produce white, blue, yellow, purple, red and multicolored flowers right through winter into spring, a big return on a small investment in money and time. Though often referred to as annuals, they are hardy to USDA zone 2.
The modern pansy began in the early 19th century with experimental crosses of the common European wildflower, the johnny jump-up or heartsease, Viola tricolor, with other violet species. The product of these crosses was named Viola x wittrockiana.
The name pansy was originally applied to V. tricolor and comes from the French word "pensee" meaning thought, supposedly applied because of the resemblance of the flower to a human face.
The first winter flowering pansy to be introduced, in 1979, was the "Universal" strain, bred for compactness, the ability to flower in winter and tolerance for wet, windy weather.
Winter pansies have flowers that are somewhat smaller than the ordinary pansy, which has been bred for flowers of large size and brilliant color that, unfortunately, tend to flop over in wet weather. They have the same pansy "faces," the blotches of black over a base color of blue, yellow and white, or a combination of these. The leaves are rounded and slightly toothed and the whole plant is 5 to 10 inches high.
Winter pansies are best planted in fall, allowing them to grow a substantial root system before spring. Choose a spot in full sun or plant in containers. Since the flowers will face the sun, plant them facing south.
Add extra compost, steer manure or other organic matter to the soil before planting and, if your soil is acid, add ground limestone to bring the pH up to 6.5 to 7.0. Pansies grow poorly and are short-lived in the acid soil that is suitable for rhododendrons and blueberries.
Fertilize once a month with a liquid fertilizer and, once the weather warms up, keep the roots moist but not wet. In early spring, shear the plants back so they can get a fresh start and then dead head them regularly, cutting off the old flowers to prevent them from setting seed. Slugs are the major pest to contend with, so put Sluggo, a product that is non-toxic to anything but slugs and snails, around your planting regularly.
Winter pansies make excellent companions for spring bulbs, reaching their full growth before the daffodils and tulips shoot up in February and March. They do well in containers, and if you live in an area with particularly cold winters, you can shift the pots into a protected spot during the worst weather. You can also place containers in protected entries to encourage more flowers in December. Winter pansies also seem to look well with vegetables, brightening a patch of hardy green onions and chard early in the spring.