Iris is a genus of about 300 species. They have three large petals on the outside called “falls”, which are curved downwards and three inner petals called “standards”. Iris comes in a rainbow of colors including blue, purple, white, yellow, pink, orange, brown, red and black. Irises are available in different sizes, which range from dwarf species (5 cm or 2 inches) to much larger varieties (130 cm or 4 ft). Iris performs best in moist and well drained soil that is slightly acidic.