Last Autumn I planted a whole bunch of Allium 'Cowanii' bulbs and I am loving how they look in my borders...
Open clusters of pure white flowers appear in late spring or early summer, creating a soft, lacy effect. The flowers last for ages after being cut and the bees will find them very attractive, so try to plant them in large numbers.
Plant in fertile well drained soil at approx 15cm apart and at a depth of roughly 3 to 4 times the size of the bulb. Avoid excessive moisture from late summer when they become dormant. Over-large clumps can be lifted and divided in autumn or spring.
Leave untouched for a number of years until the bulbs have multiplied to the extent that flowering potential is impeded.