Giant Allium  is a garden showstopper, producing large, 6-8-inch flower heads with a multitude of star-shaped lilac-colored blooms, on sturdy stalks of 4-5 feet. Giant Allium’s flowers are long blooming and are excellent to use as cut flowers. Allium giganteum is  easy to grow in full sun to part shade and dry to average, well-drained soil.
Give the plants regular water during the growing season, with a good soaking once a week or more if the weather turns extremely hot. A layer of mulch, about 3 inches deep, helps the plants retain moisture. Vegetable alliums do best with an application of a balanced, vegetable fertilizer applied as directed. Or, plant some peas in the garden bed a few months before planting the alliums and turn the peas into the soil before sowing the allium seeds in order to take advantage of their nitrogen-fixing capabilities.