Giant Ragweed
Giant Ragweed, Horseweed, Great Ragweed
(Ambrosia trifida L.)
Asteraceae (Aster Family)
▲ ▼ seedlings
▲ young plants
▲ ▼ leaves
▲ ▼ leaves
▲ ▼ immature plants
▲ stem, showing hairs, ridges
▲ ▼ mature, flowering plants
▲ ▼ mature, flowering plants
▲ ▼ mature, flowering plants
▲ ▼ inflorescences
▲ ▼ inflorescences
▲ ▼ male inflorescences (above) at top of spike; female inflorescences (below) at bottom
Ambrosia trifida L., Giant Ragweed: (Bayer Code: AMBTR; US Code AMTR)
- Is a moderately-branched, large summer annual weed (normally 3-8 feet tall, but can grow up to 15 feet tall or more)
- Spike inflorescence larger, longer than common ragweed; also allergenic
- Leaves are 3-5 lobed and much larger than common ragweed or lanceleaf ragweed
- Prefers moist, well-drained soils (becomes truly giant in river bottom soils)
- Often seen along ditches and on woodland perimeters
- Is a fast-growing, aggressive competitor in agronomic, vegetable crops