Tree Peony. No seedling number. Pod parent a Rockii hybrid of unknown origin, pollen parent an unknown Japanese tree peony. First bloomed 1999. First propagated 2003. SEMI-DOUBLE flowers, 20 cm (8 inches) in diameter, bluish pink fading to white as flower ages, one (sometimes two) buds per stem. Petals are rounded, with dark, nearly black flares. Fragrance, but not strong. Carpels 5 or more in number, pale green, moderately hairy. Stigmas white, normal. Has stamens and pollen, produces seeds. Sheath white, complete. Foliage green, suffused purple. Upright spreading growth to 2 m (6½ feet). Named in honour of Johann Sebastian Bach with his Passacaglia in C-Minor in mind. The derivation of passacaglia is from the Spanish “pasar una calla” (to go along the street), and the peony’s original planting site was in the garden, along the street.