Allium Sphaerocephalon This unique and understated allium with unusual oval-shaped, purple-green flower heads perches atop tall, slender stems. Like all Alliums, this bulb is easy to grow on well-drained soil, and will pretty much take care of itself. Sphaerocephalon must be planted in bold groups to appreciate it at its best. Grow them in dense clumps among other perennials – they associate particularly well with swaying grasses. The perfect choice for sunny borders and gravel gardens. Height: 90cm (36). Spread: 8cm (3).