The beautiful Dalia (Dahlia) flower. Kolkata, India. January 27, 2007. Dalia is a flowering plant from Mexico. There are about 30,000 species. Plants come in a wide array of sizes and forms from as low as 12 inches to as tall as 6-8 feet with flowers ranging from half-inch to giant sizes. The blooms are curvaceous, spiky with single or double forms. Colors range from white to red, orange to yellow, pink to dark purple and shades thereof.