Ruellia is a very easy to grow shrub that reaches 3 to 4 ft in height with purple flowers that constantly bloom from Spring through the Fall. Fast growing in partial to full sun, Ruellia can become invasive in moist garden soil, spreading by it's root system and reseeding easily. Purple is the most common, however there are varieties with white (Icicle) and pink (ChiChi) flowers available. There is a dwarf version called Katie that only grows to about 15' high and does not spread so easily. Katie also comes in purple, white and pink.