Ornamental onions (Allium) are hardy flowering bulbs that provide dramatic, spherical blooms in the late spring and early summer garden. Related to culinary staples like garlic and chives, they offer a unique combination of structure and color. Once flowering concludes, gardeners face two primary questions: whether to remove the spent flower head (deadheading) and what to do with the fading foliage. The answers directly influence the health and vigor of next year’s display.
Deciding When to Deadhead Alliums
Deadheading is not necessary for the health or reblooming of ornamental alliums, as they flower only once per season. The decision is largely a matter of personal preference regarding garden aesthetics or maintenance goals. Many gardeners leave the dried flower heads for architectural interest, as they remain standing upright for weeks or months and provide a source of food for wildlife.
However, some varieties, such as Allium ‘Purple Sensation’ and drumstick alliums, can self-seed aggressively. To prevent these seedlings from spreading, remove the spent bloom before the seeds fully ripen. Deadheading also directs the plant’s energy away from seed production and toward increasing the size and health of the underground bulb, potentially supporting a larger display the following year.
The Process of Removing Spent Blooms
If you decide to deadhead, the process is straightforward, requiring only clean, sharp hand pruners or scissors. The goal is to remove the flower head and the long stalk, known as the scape.
The cut should be made as close to the base of the plant as possible, near where the flower stalk emerges from the leaves. If the leaves are already beginning to yellow, you can cut the entire stalk down to the ground level. Ensure your tools are clean to prevent the spread of fungal diseases.
The Importance of Foliage
The proper handling of the foliage is the most important maintenance task for ensuring future allium blooms. The leaves are the plant’s energy factories, playing a role in the life cycle of the bulb. Through photosynthesis, the green leaves capture sunlight and convert energy into carbohydrates, which are then stored in the underground bulb.
This stored energy fuels the formation of next year’s flower bud and supports subsequent spring growth. Cutting the foliage while it is still green interrupts this process and may result in weaker blooms—or no blooms at all—the following season. Resist the urge to tidy up the fading leaves by cutting, braiding, or tying them, as this reduces the surface area available for sunlight absorption.
The leaves must be allowed to yellow and wither naturally, which typically takes about six weeks after the flower fades. Once the foliage has turned completely brown and dry, it is safe to remove it at ground level. All the stored energy has then been successfully transferred to the bulb. Planting the bulbs among low-growing perennials like Hostas or Geraniums can help disguise the dying foliage during this necessary period.