Violas are small, short lived perennials that present small pansy like flowers with 5 petals in a multitude of color combinations above glossy delicate green foliage.
In my zone 7 garden I can count on violas to add color from fall to late spring. If I am expecting a stretch of seven to ten consecutive cold winter nights with temperatures below 30 degrees, I simply cover the plants with an old sheet until morning. Violas are more heat tolerant than pansies so I keep them around until it is time to plant summer color. In cooler Northern climates violas can be planted in spring and used well into the summer if they are planted in partial shade, which is another great thing about violas, they even bloom in low light conditions.
I can remember a time when violas came in a pretty limited range of color. These days the selection is much broader. One of my favorite violas is a variety with creamy white lower petals and upper petals that are brushed with azure blue. In the fall I pack these plants around the edges of my raised vegetable beds. By the time my spring lettuce is mature the petite faces of the violas crowd together making quite an impact. I also like to mix violas with its larger cousin, the pansy. Combining the two plants in large drifts gives my garden a relaxed feel, a little less like a strip mall and more like an English cottage garden. This year I've interplanted azure and cream violas and a pale yellow variety and deep blue pansies. I've used this combination to over plant a large quantity of 'Francoise' tulips. Their creamy white blooms marked with sulfur yellow flames will be the perfect complement to the colors of the pansies and violas.