This grower is sure of this plant identification.
non seeding short growing variety
Allium genus (Onion). This genus consists of perennials, some of which are edible with bulbs, rhizomes or fibrous rootstocks. They will nearly all have basal leaves which smell of onions when crushed. Most of them have small flowers which are packed together in a dense spherical or shuttlecock shaped umbel.
They are fully to frost hardy, and will require an open, sunny situation with well drained soil. If left undisturbed a clump can be formed. Plant at a depth of approximately 12cm.
Grown for bulbs (which can be edible) and flowers, and foliage which can be decorative and/or edible, depending on the species. Dried umbels of tall border species are used for winter decoration. Suitable for coastal conditions.