Paeonia Green Halo. Introduced in 1999, semidouble, stands out with its unusual, yet classic combination of white and chartreuse. The outermost petals, called the guard petals, have a light green base and enclose a full center of pure white petals. These beautiful blossoms measure about 4 1/2 inches across, are slightly fragrant, and have good substance. Blooms Early midseason. Stunning!!