Each color has a different wavelength. Red has the longest wavelength and violet has the shortest wavelength. When all the waves are seen together, they make white light. When white light shines through a prism, the white light is broken apart into the colors of the visible light spectrum. Water vapor in the atmosphere can also break apart wavelengths creating a rainbow.
At maturity, the typical Blackeyed Susan (Hirta) will reach up to 1 foot high, with a maximum height at 20 years of 0 inches. The Blackeyed Susan (Hirta) is easily found in nurseries, garden stores and other plant dealers and distributors.
F. Rudbeckia subtomentosa, another wild one with somewhat different flowers. This Black-eyed susan is native to the central US from Wisconsin to Texas. It grows to only about 4 Â½ ft, and its flowers are distinguished by blunt tips on each petal. A commercial cultivar from this species is Henry Eilers, which grows to 4 feet and has large, tubular petals with blunt tips.