Pansies (ht 20-30 cm) are derived from cross-breeding of several Viola species, including V. tricolor, and they have larger flowers than any of their parents - up to 10 cm across in some cultivars. Leaves are heart shaped and lush. The flowers can be all one colour; bicoloured; or with central markings that look almost like little faces. The colour range of the flowers is very wide and includes almost every hue of the rainbow - and even black! They need a sunny position with good, humus-rich soil and do better if given plenty of water and regular liquid fertiliser. I also think they like a bit of lime added to the soil if it tends to be on the acidic side. They are well suited to being grown in pots. The best time to plant them out seems to be autumn, to give them time to establish their root systems whilst the weather is mild. They will begin flowering in late winter and blooming will continue throughout spring. Pinching off the spent flower heads will keep them in bloom for an extended period.
In recent years, groundcover-like cultivars such as 'Spreading Violet Wing' have been released, which form a 60 cm wide carpet or which can be used to cascade over retaining walls or in baskets.