What create broken tulip so highly valued by the seventeenth-century dutch?

Especially valued were the bi-colored tulips, known as 'broken' tulips. Tulip bulbs naturally produce only solid color blooms. If aphids infest the bulb, an insect-borne disease causes the flower's color to streak in broken lines against white petals. As the bulb blooms year after year, the streaked patterns change, becoming more erratic. But the disease also weakens the bulb, killing the plant prematurely.