Spurge is a common and aggressive broadleaf weed that quickly colonizes lawns, gardens, and sidewalks during the warmer months. Its low-growing, mat-forming habit allows it to choke out turfgrass and thrive in thin or damaged areas. Managing this annual invader requires a two-pronged chemical approach involving both preventative and corrective measures. This guide clarifies the specific chemical compounds and application timing necessary for effective control.
Identifying the Target: Spurge Varieties and Life Cycle
The most common types are Spotted Spurge (Euphorbia maculata) and Prostrate Spurge, both summer annuals. These weeds are easily identified by their sprawling growth pattern, radiating outward from a central taproot to form dense, circular mats close to the ground. A distinguishing characteristic is the milky-white sap, or latex, that oozes from the stems when broken, which is a mild irritant.
The annual life cycle of spurge dictates the timing of control methods. Spurge seeds begin to germinate in the late spring or early summer once soil temperatures consistently reach the 60°F range. The plant grows rapidly throughout the summer, producing thousands of seeds that fall into the soil before the plant is killed by the first hard frost of autumn. The seeds then remain dormant over the winter, ensuring a renewed infestation the following year.
Preventing Spurge: The Role of Pre-Emergent Herbicides
Pre-emergent herbicides serve as the first line of defense against future spurge infestations by targeting the seeds before they sprout. These products work by forming a chemical barrier near the soil surface that disrupts the cellular division in the seedling roots as they emerge. The herbicide must be in place before the spurge seeds germinate, as pre-emergent products have no effect on weeds that have already emerged.
For spurge control, effective pre-emergent products often contain active ingredients like Prodiamine, Pendimethalin, or Dithiopyr. The optimal time for application is in the spring when the soil temperature consistently reaches 55°F, just ahead of the 60°F germination point for spurge. Applying the treatment too early may cause the chemical barrier to degrade, while applying it too late will miss the critical window.
Dithiopyr, often sold under the trade name Dimension, is a popular choice because it offers a small window of post-emergence activity on very young spurge plants, in addition to its primary pre-emergent function. Prodiamine provides a long residual control period, helping to keep the lawn protected throughout the summer growing season. Following the application, these granular or liquid products typically require a light watering or rainfall to activate the chemical barrier in the top layer of the soil.
Eliminating Existing Spurge: Effective Post-Emergent Treatments
When spurge is already visible and actively growing, a post-emergent herbicide is necessary to eliminate the established plants. These chemicals are absorbed by the leaves, where they then translocate through the plant to kill the entire structure, including the taproot. Spurge is most susceptible to these treatments when the plants are young and small, before they have formed large, dense mats and set seed.
The most effective chemical solutions for killing existing spurge are selective broadleaf herbicides, formulated to target the weed without damaging the surrounding turfgrass. These products are typically hormone-mimicking compounds, often sold as a “three-way mix” that combines several active ingredients for a broader spectrum of control. A common combination includes 2,4-D, Dicamba, and either MCPA or MCPP, which work synergistically to disrupt the weed’s growth hormones.
Triclopyr is also an effective component, sometimes used in place of or in addition to MCPA in these three-way blends. These auxin-type herbicides cause the spurge to grow in an uncontrolled, distorted manner, ultimately leading to the plant’s death. For maximum effectiveness, the herbicide should be applied to the foliage of the actively growing weed, ensuring thorough coverage but not runoff. Visible results, such as wilting and browning, are typically seen within one to two weeks following a proper application.
Application Guidelines and Safety Considerations
Regardless of whether a pre-emergent or post-emergent product is used, following specific application guidelines is necessary for both efficacy and safety. Always read the product label entirely before mixing or applying any chemical, as this document contains the legal instructions for safe use and application rates. The label will specify the proper Personal Protective Equipment (PPE) required, which typically includes:
- Long-sleeved shirts
- Long pants
- Chemical-resistant gloves
- Eye protection
Environmental conditions play a significant role in successful application and drift prevention. Avoid spraying herbicides when wind speeds exceed 10 miles per hour to prevent the product from drifting onto non-target plants. High temperatures, especially those above 85°F, can cause active ingredients like Dicamba to volatilize, meaning the chemical turns into a vapor and can drift, potentially damaging desirable plants. After application, keep pets and children away from the treated area until the spray has completely dried, which is typically a few hours.