'Star Gazer' is a compact, upright, rounded, deciduous shrub with broadly ovate, toothed, veined, dark green leaves and, in summer, sturdy stems bearing large, flat flowerheads of double, star-shaped flowers, blue with white petal margins in alkaline soil and pink with white petal margins in acid soil. Grow in moist but well-drained soil in sun or partial shade. Will perform best with afternoon shade. Soil ph effects flower colour -flowers turn blue in acid soil, pink on neutral to alkaline soil..