1 litre sized pot.  Verbena rigida is a herbaceous perennial and a smaller, slender variety of verbena compared to Verbena bonariensis.  It has clusters of deep purple-magenta flowers from mid-spring onwards.  It has long toothy mid-green leaves.  It likes full sun and given good drainage will come through mild-moderate winters.  Beneficial for attracting insects, particularly butterflies, reaches 45-60cm.