Garlic Chives are very useful. They come back year after year and provide clean, white blooms, clustered at the top of strong (relatively), single stems in late summer/early autumn. They can be used for cooking. They can be easily seeded to fill in empty spots in a perennial bed, and they make a perfect, knee-high edging plant for a long border. They are architectural because they have strong structure and the blooms remain a reliable, uniform height.
This is an easy-care plant. It can tolerate Zone 3 cold, and will remain evergreen in Zone 8. Even though it is invasive in Australia, you can control it without much trouble. The seed heads open late in the season. They are held compactly at the top of the stems. If you catch them before the seed clusters dry and the large, black seeds start popping out, you can control its spread. All it asks for is sunshine and water.