Dianella is one of those less well known perennials that is often mistaken for another plant. Case in point, 'Clarity Blue' dianella could be mistaken for New Zealand Flax, with its upright, strap-like leaves, but it has its own interesting qualities. Most noticeable is its blue-green coloring, something you don't usually see in the phormium family. 'Clarity Blue' is also much more compact, growing 24 to 30 inches tall and spreading 18 to 24 inches wide. Small blue flowers appear in the spring, though this variety's foliage is the main attraction. Both New Zealand flax and dianella are deer-resistant, but dianella tends to be more drought-tolerant once established. 'Clarity Blue' is hardy down to 0 degrees, but it may do best in container planters so it can be moved to a protected area in extreme cold.