Sweet William 'Crown Double' (mixed) is a herbaceous biennial or short-lived perennial plant growing to 13–92 cm tall, with flowers in a dense cluster of up to 30 at the top of the stems. Each flower is 2–3 cm diameter with five petals displaying serrated edges.
Wild plants produce red flowers with a white base, but colours in cultivars range from white, pink, red, and purple to variegated patterns.
The flowers are edible and may have medicinal properties.
Sweet William attracts bees, birds, and butterflies.