Dogfennel Identification and Control in Pastures and Landscapes

Recognizing Dogfennel

Dogfennel (Eupatorium capillifolium) is a 3-4 foot tall perennial with finely divided, fern-like foliage and small white flowers. Don't confuse it with Anthemis cotula (mayweed), which shares the common name "dog fennel" but is a completely different annual weed.

Why It's Problematic

Historically, dogfennel infestations in pastures caused milk to develop off-flavors when cows grazed it. While cattle generally avoid eating it, they also avoid grazing around clumps, reducing usable forage. In landscapes, its aggressive spreading habit can crowd out desirable plants.

Control Strategies

Since dogfennel regenerates from root fragments, mechanical removal requires extracting the entire root system. For larger infestations, herbicide options include:

• Glyphosate (Roundup) – non-selective, apply to actively growing foliage
• Triclopyr (Brush-B-Gon) – selective for broadleaf weeds, safer for grasses

Multiple applications may be needed for established stands. Some gardeners appreciate dogfennel's airy texture and late-season flowers, so consider whether it fits your landscape goals before removing.