Butterweed (Packera glabella) is a widespread plant found in various landscapes, particularly agricultural and disturbed areas. While often seen as a common weed, this species plays multiple roles in its environment and interacts with human activities. Its presence can signal specific ecological conditions, offer benefits to certain organisms, and pose challenges, especially in livestock management. This article explores butterweed’s characteristics, ecological contributions, and toxicity.
Identifying Butterweed
Accurate identification of butterweed is essential for effective management. This annual plant typically grows 1 to 3 feet tall. Its stems are hollow and ribbed, often displaying a greenish-purple or reddish-purple tint, particularly towards the base.
Initial rosette leaves are deeply lobed with rounded, serrated margins, and can be purple on their undersides. As the plant bolts, stem leaves are alternately arranged, becoming progressively smaller towards the top, and are also deeply divided and lobed. In spring, bright yellow, daisy-like flowers emerge in clusters at the stem tips, each with 5 to 15 ray petals surrounding a central disk. Butterweed thrives in moist, often disturbed soils, such as floodplains, pastures, and roadsides.
Ecological Contributions
Butterweed offers several ecological contributions. As an early spring bloomer, it provides vital nectar and pollen resources for various pollinators, including bees and other insects, when other food sources may be scarce.
As a winter annual, its seeds germinate in the fall, forming rosettes that overwinter. This allows it to act as a pioneer species in disturbed areas, helping to cover bare soil and aid in erosion control and soil stabilization during cooler months. Its presence in natural, moist environments contributes to local biodiversity.
Toxicity and Livestock Impact
Butterweed is toxic due to pyrrolizidine alkaloids (PAs) found throughout the plant, including leaves, stems, flowers, and seeds. These compounds cause liver damage in animals that ingest them, leading to progressive liver cirrhosis or acute liver necrosis.
Livestock such as cattle, horses, and goats are susceptible to butterweed poisoning. Symptoms include listlessness, decreased appetite, weight loss, jaundice, and neurological signs like uncoordinated movement. Ingesting large quantities can lead to acute liver necrosis and death. Chronic exposure, even at lower concentrations, also results in severe health issues and mortality. While animals generally avoid fresh butterweed, its toxicity is not reduced when dried in hay, making contaminated hay a particular concern.
Controlling Butterweed
Managing butterweed populations is often necessary, especially in agricultural settings where it can impact livestock or compete with desired crops. Manual removal, such as pulling or mowing plants before they produce seeds, is one effective strategy to prevent spread.
Cultural practices also help minimize butterweed. Maintaining healthy, dense pastures can outcompete the weed, as butterweed thrives in disturbed or thin stands. Implementing good crop rotation and using winter cover crops can suppress its germination and growth.
For chemical control, herbicides containing 2,4-D are effective, particularly when applied to plants in the rosette stage during fall or early spring before flowering. Specific herbicides like GrazonNext HL or Milestone can provide control at various growth stages. However, timely application is important, as larger, flowering plants become more difficult to control chemically.