Dogfennel (Note: This is an herbaceous biennial/perennial weed, not a true grass)
Eupatorium capillifolium · Perennial weed; C3 photosynthesis; warm-climate adapted
Grass Family
Asteraceae (Sunflower family); Tribe: Eupatorieae
Grass Category
Invasive/Weed Grass (Misidentified by form; actually a broadleaf weed)
Variety / Cultivar
Native wild type
Hardiness Zones
USDA Zones 3-10 (most aggressive in 7-10); dies back to the ground after heavy frost and re-emerges in spring.
About This Grass
An upright, feathery, multi-branched herbaceous plant that resembles a fine-textured grass from a distance. Can grow 3-6 feet tall. Lime-green color; emits a strong, pungent odor when crushed. Mature plants develop panicle-like clusters of tiny white flowers at the top.
Blade Characteristics
Leaves are thread-like, highly dissected, and needle-fine (<1mm); arranged alternately or in whorls; no ligule or auricles (non-poaceous structure); texture is soft and airy.
Root System
Deep, woody taproot combined with a creeping rhizomatous network; very high thatch-like biomass; difficult to pull once established.
Growing Information
Origin Region
Native to North America (Southeast and East Coast); thrives in USDA zones 7-10
Growth Habit
Clumping/Bunch-type with a woody base; spreads via wind-blown seeds and aggressive underground rhizomes
Sunlight & Water Needs
Full Sun; very low water needs; extremely drought tolerant; prefers disturbed sandy soils but adapts to various pH levels.
Mowing & Maintenance
Not for mowing; survives mowing by regrowing from base. Management requires pre-emergent herbicides or frequent low-mowing to prevent seed set. Maintenance level: High (as a weed).
Special Characteristics
High tolerance to poor soil and drought; contains alkaloids that are toxic to livestock (cattle/horses); extremely effective at crowding out pasture grasses.
Ecological Information
Native to the US; serves as a host for some wasp species and provides cover for small mammals, but is generally considered an aggressive pioneer species in overgrazed pastures or disturbed lots.