In my zone 7 garden I can count on violas to add color from fall to late spring. 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.
If I am expecting a stretch of 7 to 10 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.