Dog Fennel is a perennial broadleaf weed that is also known as Summer Cedar, Hogweed and Eupatorium capillifolium.
Dog Fennel can be identified as a short-lived broadleaf weed that has a thick, woody base. Its multiple stems are vertically growing and multibranched in the upper flowering portion while hairy or sometimes smooth below. The color is more reddish-purple toward the base. Dog Fennel leaves are pinnately dissected once or twice into fine linear segments. Dog Fennel produces flowers that resemble daisies. These flowers, along with the leaves, emit a strong, foul odor when crushed. Dog Fennel has a fibrous root system and reproduces by seeds.
This broadleaf weed prefers moist to wet areas, but it doesn't fare well in thick, established lawns. Instead, it grows best in poorly maintained grasses and other waste areas. In the United States, Dog Fennel can be found along the East Coast from New Jersey to Florida and west into Missouri and Texas.
Eupatorium capillifolium does not typically invade lawns with thick, well-maintained and established grass. Cultural weed control practices offer a good preventive measure, including proper lawn mowing and watering habits. However, once Dog Fennel is present in your lawn, professionally applied broadleaf weed killers are best for complete removal.