Parthenium hysterophorus (Santa Maria feverfew)

1 / 3

Parthenium spp.

wild quinines

Asteraceae

Americas; center of diversity in Mexico and the southern United States

Attracts Pollinators Deer Resistant Drought Tolerant

Native to North America

SunFull Sun

WaterLow · drought-tolerant

HardinessZones 4–11

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

Recognized by small white to cream flower heads 0.2–0.4 inch (5–10 mm) across, each with five short, rounded ray florets, held in flattened clusters. Leaves are alternate and rough to the touch, ranging from lance-shaped and entire to deeply lobed. Separated from related aster genera by the five fertile ray florets that each set a single seed, rather than seed set from the disc florets.

Appearance

Size & Dimensions

Height1' - 10'

Width/Spread1' - 4'

Colors

Flower Colors

Foliage Colors

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 cream

Foliage Description

green to silvery-green

Growing Conditions

Sun Requirements

SunFull Sun

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

Soil Requirements

pH Range6.0 - 7.5(Neutral)

357912

Soil Types

loam sand rocky

Drainagewell drained

Water & Climate

Water Needs

Low

Drought Tolerance

Drought tolerant when established

Care & Maintenance

Care Guide

Most species grow in full sun and well-drained soil with low to moderate water once established. P. integrifolium tolerates drought and poor, rocky soils, while desert species such as P. argentatum need sharp drainage and minimal irrigation. Seed germinates in warm soil, and self-sown seedlings appear around established plants. Weedy annual species set thousands of seeds per plant and recur from the seed bank for several years. Aphids and powdery mildew occur occasionally but seldom reduce growth. Contact with sap or pollen causes skin and respiratory irritation in sensitive people.

Pruning

Herbaceous species can be cut to the ground in late fall or early spring after stems die back. Removing spent flower heads before seed matures reduces self-seeding, which is heavy in weedy species. Shrubby species such as P. argentatum need little cutting beyond removal of dead wood.