Federal Noxious Weed Disseminules of the U.S.

Arctotheca calendula (L.) Levyns

(=Arctotis calendula L.; Cryptostemma calendula (L.) Druce)

Family: Asteraceae, Tribe: Arctoteae

Common names:  capeweed

Disseminule:  Fruit

Description

Fruit an achene, obovate, flattened, with a mildly lobed collar at the apex, 2–4(5) mm long, 1.0–1.4 mm wide, 0.7–1.0 mm thick; cross-section elliptic with distinct ridges at the margins to rhombic with a total of 3–5 longitudinal ribs; surface dark brown, granular, rugose, pubescent with long, crinkly light brown hairs that envelop the fruit to create a ball 6–8 mm diameter. Scar basal, round. Persistent pappus of 6–8 lanceolate scales, ca. 0.8 mm long each, yellowish-purple with purple veins. Style base dark brown, cylindrical. Embryo spatulate; endosperm absent.

Identification considerations

The ball of woolly hairs encasing the fruit is distinctive.

Distribution

Native to southern Africa.

Naturalized in Australia, New Zealand, Portugal, southwestern Spain, the Azores and California, United States.

Habitat

The natural habitat includes sand dunes, stream banks and rocky outcrops. Capeweed prefers sunny sites and sandy, well-drained soils. It is a tough plant, withstanding drought conditions. As a weed, it invades pastures, yards and disturbed sites, outcompeting other vegetation.

General information

Arctotheca calendula is a rosette-forming perennial. Fruits are believed to be wind-borne and may become lodged in animal fur. Human activities that result in the movement of contaminated soils can spread both fruits and stolons. International dispersal is sometimes intentional, the plant being valued as an ornamental groundcover and for medicinal purposes. Unintentional spread may occur via contaminated fleece, grain or seed shipments from South Africa or Australia.