Parthenium Species, Congress Weed, False Ragweed, Santa Maria Feverfew, White Top Weed
Partheniumhysterophorus

Family: Asteraceae (ass-ter-AY-see-ee)
Genus: Parthenium (par-THEN-ee-um)
Species: hysterophorus (his-ter-oh-FOR-us)

Synonym:Parthenium lobatum

Synonym:Parthenium pinnatifidum

Category
Annuals

Water Requirements

Sun Exposure
Full Sun

Foliage
Herbaceous

Foliage Color

Height
18-24 in. (45-60 cm)
24-36 in. (60-90 cm)
36-48 in. (90-120 cm)

Spacing
18-24 in. (45-60 cm)

Hardiness
Not Applicable

Where to Grow

Danger
Handling plant may cause skin irritation or allergic reaction
Pollen may cause allergic reaction

Bloom Color
White/Near White

Bloom Characteristics

Bloom Size

Bloom Time
Mid Summer
Late Summer/Early Fall
Mid Fall
Late Fall/Early Winter

Other details
May be a noxious weed or invasive

Soil pH requirements
6.1 to 6.5 (mildly acidic)
6.6 to 7.5 (neutral)
7.6 to 7.8 (mildly alkaline)

Patent Information
Non-patented

Propagation Methods
From seed; direct sow outdoors in fall
Self-sows freely; deadhead if you do not want volunteer seedlings next season

Seed Collecting
N/A: plant does not set seed, flowers are sterile, or plants will not come true from seed