Parthenium spp.
wild quinines
Americas; center of diversity in Mexico and the southern United States
Overview
Parthenium spp. is a genus of roughly 16 species in the aster family (Asteraceae), ranging from herbaceous annuals and perennials to woody shrubs. Plants reach 1–10 feet (0.3–3 m) tall depending on species, with P. integrifolium forming clumps 2–4 feet (60–120 cm) tall and the shrub P. argentatum reaching 1.5–3 feet (0.5–0.9 m). Foliage is alternate, with leaves ranging from entire and lance-shaped to deeply lobed or toothed, 2–8 inches (5–20 cm) long, often rough-textured or covered in silvery hairs. Flower heads are small, 0.2–0.4 inch (5–10 mm) across, white to cream, carried in flat-topped or branched clusters from late spring through fall. Each head holds five short, rounded ray florets surrounding a central disc. Seeds form in small, flattened achenes. Growth habit varies from upright single stems to multi-stemmed mounds. Several species, including P. hysterophorus, spread by seed and are listed as agricultural weeds across warm regions. Sap and pollen of some species cause contact dermatitis and respiratory irritation in sensitive individuals.
Native Range
Native to the Americas, with the center of diversity in Mexico and the southern United States. Species occupy prairies, open woodlands, deserts, and disturbed ground from sea level to about 8,000 feet (2,400 m). P. integrifolium ranges across the eastern and central United States, while P. argentatum is restricted to the Chihuahuan Desert of Texas and northern Mexico.Suggested Uses
P. integrifolium is grown in prairie and native-plant gardens and cut for arrangements, spaced 18–24 inches (45–60 cm) apart. P. argentatum is cultivated in arid regions as a source of natural rubber and latex. Weedy species are managed as invasive plants in pastures and croplands.How to Identify
Appearance
Size & Dimensions
Height1' - 10'
Width/Spread1' - 4'
Bloom Information
Flowering runs from late spring through early fall, typically May to September in temperate species and nearly year-round in subtropical annuals such as P. hysterophorus. Individual flower heads last 1–2 weeks, with clusters opening in succession over 6–10 weeks. Warm temperatures and open, disturbed ground extend the flowering and seeding period.
Detailed Descriptions
Flower Description
white to creamFoliage Description
green to silvery-greenGrowing Conditions
Sun Requirements
Requires 6-10 hours of direct sunlight daily
• Full Sun: 6+ hours of direct sunlight
• Partial Shade: 3-6 hours of direct sunlight
• Full Shade: Less than 3 hours of direct sunlight
Water & Climate
Water Needs
Drought Tolerance
Drought tolerant when established