Star of Bethlehem (Ornithogalum umbellatum) is a persistent, invasive perennial plant that often becomes a widespread nuisance. This bulb-forming species emerges early in spring, displaying narrow, grass-like leaves and distinctive white, starry flowers. Its aggressive reproductive strategy makes it challenging to control once established. Complete eradication requires a methodical approach that targets the plant’s underground structures and exploits its short seasonal life cycle.
Identifying the Target and Its Weaknesses
Identification begins with its unique foliage, which is often mistaken for wild garlic or wild onion, but lacks their characteristic odor. The leaves are long, glossy, and narrow, featuring a prominent, light-colored stripe down the center of the upper surface. This plant is invasive because it reproduces prodigiously through vegetative offsets, known as bulblets, which are miniature versions of the main bulb.
The parent bulb, typically an inch long, can produce up to seven new bulblets annually, leading to dense colonies. These bulblets act as underground storage units, allowing the plant to survive adverse conditions and re-emerge the following season. The plant’s greatest weakness is its short window of active growth, which begins in late winter or early spring. Since the foliage dies back and the plant goes dormant by early summer, control efforts must be concentrated when the plant is actively transporting energy to its underground structures.
Manual and Cultural Removal Methods
Manual removal is feasible for small, isolated infestations, but requires precision. The difficulty lies in the numerous small bulblets, which easily detach from the main bulb and are left behind, guaranteeing future regrowth. To physically remove the plant, gardeners must carefully excavate the entire clump, digging down approximately four inches and sifting through the surrounding soil to collect all bulblets.
All removed plant material, especially the bulbs, must be disposed of properly, as composting will spread the infestation. For broader infestations, cultural controls like solarization can be attempted. This involves covering the infested area with clear plastic sheeting for six to eight weeks during the hottest part of the summer to bake the soil. However, this method is often ineffective against the deeply buried, resilient bulbs. For large, established colonies, the volume of underground bulblets makes manual and cultural methods too laborious, necessitating a transition to chemical controls.
Effective Herbicide Application Techniques
For widespread infestations, systemic, post-emergent herbicides are the most reliable tool, as they are absorbed by the leaves and transported down to kill the underground bulblets. The waxy coating on the narrow leaves presents a significant challenge to herbicide absorption, often causing spray droplets to bead up and run off the surface. To overcome this resistance, adding a non-ionic surfactant to the spray mixture is recommended. The surfactant acts as a wetting agent, helping the herbicide adhere to the waxy leaf surface and penetrate the plant tissue more efficiently.
The timing of the application is paramount; herbicides must be applied during the plant’s brief window of active growth in early spring, before the foliage begins to die back. Effective active ingredients include mixtures of 2,4-D and dicamba, or commercial products containing sulfentrazone or carfentrazone, which have shown high control rates. A single application is rarely enough to achieve complete eradication because the bulblets do not all emerge at the same time. Multiple sequential applications over a single season, and often over several years, are necessary to eliminate newly emerging plants. When using any chemical, it is mandatory to strictly follow all product label directions for safety, application rate, and instructions regarding surfactants.