Allium hollandicum, popularly known as the Purple Sensation is one of the most popular species of ornamental bulbous plants. Other ornamental species of Allium include Allium cristophii, Allium caeruleum and Allium giganteum which are used as border plants.

Allium is the genus of onions with about 1250 species of perennial bulbous plants. The onion is probably native to southwestern Asia but is now grown throughout the world, chiefly in the temperate regions. There are several species of Allium or onion that are grown exclusively for their flowers instead of their bulbous structures. Ornamental onions are not planted in the vegetable garden, but in beds or borders with other perennial flowers. Flower heads on ornamental onions are usually globe shaped and appear in late spring to mid summer.

Allium plants vary in height between 5 cm and 150 cm. The flowers of allium form an umbel at the top of a leafless stalk. Alliums have strappy, undistinguished leaves and straight tubular flower stalks. The flower form in clusters and are best known in the round pom-pom form, but they can be start shaped, cup-shaped, semi-circular or pendulous.

The Allium bulbs vary in size between species, from very small to rather big. Some species (such as chives, Allium schoenoprasum) develop thickened leaf-bases rather than forming bulbs. Most bulbous alliums increase by forming little bulbs or offsets around the old one, as well as by seed. Several species can form many bulbils (tiny bulbs) in the flowerhead; in the so-called tree onion (Allium cepa Proliferum Group) the bulbils are few, but large enough to be used for pickling.

  • Onions were used extensively by the ancient Egyptians, as shown by drawings and inscriptions on their monuments.
  • The wide use of alliums as ornamental plants is a more recent phenomenon, first gaining favor about the middle of the 19th century.
  • Onions are among the world's oldest cultivated plants. They were probably known in India, China, and the Middle East before recorded history. Ancient Egyptians regarded the spherical bulb as a symbol of the universe.

  • Most alliums grow best in average to rich, well-drained soil in full sun. Some Alliums need excellent drainage and dry conditions after flowering.
  • Plant new bulbs in the fall and divide crowded clumps after they are done flowering.
  • Small bulbs of should be planted at 4 to 6 inches and large bulbs should be set at a depth of 6 to 8 inches.
  • Chives can be divided in spring or fall.

  • Alliums do not repeat bloom. Flower heads can be left on the plant to dry.
  • The dried seed heads look attractive in the garden and can be used for cutflower arrangements.
  • Keep foliage watered after flowering, to feed the plant.