Round-headed leek, or Allium sphaerocephalon, is a tall ornamental plant with a dense, spherical purple flower head. It’s grown for its looks, though the flower heads and young leaves are edible in small amounts. You’ll recognise it by its single slender stem, narrow hollow leaves, and the round cluster of tiny flowers at the top.
Picking
The flower heads are ready when they turn deep purple and feel firm, with all the florets tightly packed. The stem should still be green and upright. If the florets start to open or drop, or the stem yellows, it’s past its best.
Cut the stem about 10–15 cm below the flower head with sharp scissors or secateurs. The heads are moderately sturdy but can bruise if handled roughly, so treat them gently. Young leaves can be snipped at the base, though they’re less commonly picked. Leave the lower stem and roots—it won’t regrow after harvest.
Morning is the best time to pick, when the flowers are hydrated. The season runs from June to August, peaking in July. Heavy rain can cause the stems to snap or the flower heads to rot, and hard frost will kill the plant.
At home
Rinse the flower heads gently under cold water just before use to remove any insects or debris. Trim the stem ends if needed.
For short-term storage (1–3 days), place the stems in water like cut flowers, cover loosely with plastic, and keep them in the fridge. For up to a week, wrap the flower heads in a damp paper towel and store them in a perforated bag in the fridge. They’ll keep for 3–7 days.
Drying works: hang the flower heads upside down in a dark, dry, ventilated place for two to three weeks. They can then be used in dried arrangements or infusions. Freezing isn’t recommended—the texture turns mushy.
Cutting and arranging
Cut the flower heads when about a third to half of the florets are open. Use sharp scissors and cut the stem at an angle. Remove any lower leaves to prevent rot, and change the water every two days. Keep them out of direct sunlight to prolong their vase life.
Round-headed leek works well as a filler in bouquets or dried arrangements. In the Victorian language of flowers, alliums symbolise unity and patience.
The flower heads are non-toxic to humans and pets in small quantities, and the plant doesn’t have irritating sap.