Broom sage (Andropogon virginicus), also known as broomsedge bluestem, is a perennial grass that quickly becomes a major nuisance. This warm-season grass thrives in poor conditions, allowing it to rapidly spread and outcompete turf and forage crops. Eliminating established broom sage is challenging because its presence often signals underlying issues with soil health.
Identifying Broom Sage and Its Growth Cycle
Broom sage grows in distinctive, dense clumps, reaching heights between one and a half to four feet. Immature plants appear bluish-green, but the foliage dries out and turns a coppery-red or golden-orange color in the late summer and fall. The dried, straw-colored remnants often persist through the winter, making identification easy during the dormant season.
The plant’s common name comes from its bristly, broom-like seed heads that appear in late summer or early fall. These wind-pollinated seeds are small, numerous, and easily dispersed, explaining the plant’s aggressive spread. Since it is a perennial, it maintains a fibrous root crown and actively grows during the summer and early fall, which is the most effective time for control efforts. Targeting the plant before it produces and disperses seed is necessary to limit future infestations.
Non-Chemical and Manual Removal Strategies
For small, isolated patches, manual removal is a practical option, though labor-intensive due to the dense, fibrous root system. The entire root crown must be dug out to prevent regrowth, which is easiest when the soil is moist. Manual methods are not feasible for large areas, such as pastures or extensive fields.
Repeated mowing is another non-chemical approach that can help manage the weed, although it will not eliminate the plant entirely. Mowing at a low height consistently throughout the growing season prevents the plants from reaching maturity and producing seed heads. This repeated cutting depletes the plant’s stored energy reserves, reducing the plant’s vigor and competitive ability.
Solarization can be used in smaller areas by covering the infested ground with clear plastic sheeting for several weeks during the hottest part of the summer. This process dramatically increases the soil temperature, killing existing plants and seeds present in the upper soil layers. While effective, solarization renders the treated area unusable for a period and is not suitable for large-scale infestations. For pastures, heavy grazing in the early to mid-spring, when the young growth is still palatable, can suppress the plants by preventing them from reaching the reproductive stage.
Selecting and Applying Herbicides Safely
Chemical control is often necessary for large or dense infestations, and timing significantly impacts success. Non-selective herbicides containing glyphosate are the most effective option for controlling established broom sage. Glyphosate is a systemic herbicide that moves throughout the plant, including the roots, but it will kill any desirable vegetation it contacts.
Post-emergent application in the late summer or early fall is the most effective window for treatment. During this time, the perennial grass actively transports nutrients down to its root system in preparation for dormancy, which helps pull the herbicide deep into the root crown. Late-summer applications of glyphosate can reduce stem density by 65% to 80% one year after treatment.
Using a nonionic surfactant with the herbicide mixture is recommended, as it helps the product penetrate the plant’s waxy leaf surface, improving absorption and efficacy. Application should be done as a spot-spray to target only the broom sage, minimizing damage to surrounding desirable grasses. Always wear appropriate personal protective equipment and ensure wind speeds are low to minimize drift onto non-target plants.
Pre-emergent herbicides can also be incorporated into a long-term control plan to prevent new seedlings from establishing the following spring. These products create a chemical barrier in the soil that stops seeds from germinating. Combining a fall non-selective application with a spring pre-emergent treatment manages both established perennial clumps and annual seedling recruitment.
Preventing Recurrence Through Cultural Practices
Long-term control relies heavily on improving soil health, as broom sage indicates low fertility. It thrives in poor, acidic soils that are deficient in phosphorus. The first step in prevention is a soil test to determine the existing pH and nutrient levels.
Adjusting the soil pH with lime is necessary to create an environment where desirable grasses can thrive and outcompete the broom sage. Lime is a slow-acting amendment, so this process may take several seasons to fully correct the soil acidity. Applying phosphorus fertilizer based on soil test recommendations will help shift the competitive advantage away from the broom sage, which is adapted to low phosphorus conditions.
Establishing a dense, healthy stand of turf or forage grasses is the most reliable long-term preventative measure. Maintaining optimal fertility and proper mowing height encourages thick growth, which shades the soil and suppresses the germination and establishment of broom sage seedlings. Competitive planting effectively uses the desired plants as a biological barrier against weed return.