Clearweed vs Coastal Ragweed

Pilea fontana compared with Ambrosia hispida

Taxonomic Classification

Rank	Clearweed	Coastal Ragweed
Kingdom same	Plantae (Plants)	Plantae (Plants)
Phylum same	Magnoliophyta (Flowering Plants)	Magnoliophyta (Flowering Plants)
Class same	Magnoliopsida (Dicots)	Magnoliopsida (Dicots)
Order	Rosales (Roses & Allies)	Asterales (Daisies & Sunflowers)
Family	Urticaceae	Asteraceae (Daisy Family)
Genus	Pilea	Ambrosia
Species	Pilea fontana	Ambrosia hispida

Evolutionary Relationship

Clearweed and Coastal Ragweed share a common ancestor at the Class level: Magnoliopsida. (Dicots)

Conservation Status

Clearweed

LC — Least Concern

Coastal Ragweed

LC — Least Concern

Physical Characteristics

Attribute	Clearweed	Coastal Ragweed
Diet	—	—
Average Lifespan	—	—
Average Length	—	—
Average Weight	—	—

Habitat & Geographic Range

Clearweed

Habitat

Typically found in diverse terrestrial habitats from tropical forests to temperate regions.

Range

Distributed across Canada and United States.

Coastal Ragweed

Habitat

Typically found in diverse terrestrial habitats from tropical forests to temperate regions.

Range

Found in Cuba.

Clearweed

Clearweed, Pilea pumila, is a small, annual herb in the family Urticaceae native to moist, shaded habitats across eastern North America and eastern Asia, including the eastern United States, Canada, eastern China, Japan, and Korea. The species grows in dense colonies in wet woodland, stream banks, floodplain forests, and moist disturbed ground, often forming carpets on rich, moist mineral soils in deeply shaded forest understories. The common name refers to the translucent, watery stems and smooth, bright green leaves, which give the plant an almost glassy appearance. Like its relative stinging nettle, Clearweed is a member of the nettle family but lacks the stinging hairs, making it harmless to touch. The leaves are opposite, broadly ovate with toothed margins, and the plants bear inconspicuous tiny greenish flowers that are wind-pollinated, releasing pollen in small explosive bursts. Clearweed provides food for a variety of insects and invertebrates in moist forest understory communities. The species is not considered threatened and is common across its native range, thriving in the disturbed, humid conditions found along stream margins and in second-growth forest habitats. It is occasionally weedy in gardens and greenhouses.

Coastal Ragweed

Coastal ragweed (Ambrosia hispida) is a perennial herb in the family Asteraceae, native to the coastal dunes, sandy beaches, and cays of Cuba, the Bahamas, and the wider Caribbean region. It grows in pioneer beach and dune vegetation, often forming spreading colonies that help stabilise loose coastal sands. Like other members of the genus Ambrosia, it bears inconspicuous greenish-white flowers arranged in racemes; male flower heads produce wind-dispersed pollen that can trigger allergic rhinitis in sensitive individuals. The deeply lobed, hispid leaves are adapted to reflect intense solar radiation and tolerate salt spray. Coastal ragweed plays an ecological role in early dune succession, binding sand and enabling other plant species to establish. The genus is widespread globally, with several Ambrosia species considered noxious weeds in agricultural settings, though Ambrosia hispida is restricted to its native Caribbean coastal range. The IUCN assesses it as Least Concern, reflecting adequate population size across its Caribbean coastal distribution. Pressure from coastal development and tourism infrastructure poses a localised threat to dune communities it inhabits.