Giganteum = Giant. Allium giganteum is exactly that giant globes of purple flowers, I came across one walking down the river Thames Bank few globes of purple or violet flowers. They are eye-catching. Allium giganteum or also call Giant Onion or Giant Allium is a bulbous herbaceous perennial and is an ornamental onion plant. The leaves usually die down before the flowers, either way, they are at a much smaller scale than the flowers. This plant is native to Asia and North-East Iran. It flowers in late spring or summer. The flowers are little star-shaped lilac flowers formed in a cluster depicting a globe. The blooms are long-lasting and colorful and look nice both in the garden as well as flower arrangements.
Allium giganteum likes full sun and should be planted in moist but well-drained soil. It grows to about 1.5m or 5ft. It is easy to grow and looks good in beds and borders mixed with other flowers since its height is due to the long narrow stems of the flowers it adds height and color without shading other plants. It is easy to maintain no pruning necessary and Allium giganteum is generally pest-free. However, onion white rot and downy mildew can happen.
You can propagate this plant by seed, planting the seeds in spring. It attracts butterflies but it is deer-resistant and drought-tolerant. It has scent not necessarily a pleasant one but most onion related plants do have similar types of scent.