When to plant Ornamental Onion?

Plant ornamental onion bulbs between September and November, while the soil is still workable and before the first hard frosts arrive. Choose a spot in full sun—Allium giganteum needs at least six hours of direct sunlight daily to produce its dramatic flower heads and sturdy stems. The bulbs tolerate a wide range of well-drained soils, including loam, sandy soil, and chalky ground, but they will rot in heavy clay or waterlogged conditions. If your soil is prone to sitting wet over winter, dig in plenty of grit or coarse sand to improve drainage, or plant on a slight slope or raised bed. Dig holes roughly three times the depth of the bulb—typically 15–20 cm deep for large Allium giganteum bulbs. Space them 15 cm apart; their narrow foliage takes up little room, and close planting creates a more impressive display. Set each bulb pointy end upwards on a layer of sharp sand or grit at the base of the hole to further aid drainage around the basal plate. Backfill with soil, firm gently, and water in lightly if the ground is dry, though autumn rains usually provide enough moisture. Ornamental onions are excellent for planting in drifts through herbaceous borders or in gravel gardens. They also work well in large containers filled with loam-based compost mixed with extra grit. After planting, apply a light mulch of garden compost or leaf mould to suppress weeds, but keep it clear of the planting spots to avoid encouraging rot. The bulbs will establish roots through autumn and winter, then send up foliage in early spring.