Arctotheca calendula

Name and classification

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.

achene with hairs teased back to better reveal the fruit

achene with hairs teased back to better reveal the fruit

achene with hairs and pappus scales removed

achene with hairs and pappus scales removed

close-up of the ring of pappus scales

close-up of the ring of pappus scales

apex with scales still attached

apex with scales still attached

apex with scales removed

apex with scales removed

attachment scar of a fruit with hairs still attached

attachment scar of a fruit with hairs still attached

attachment scar of a fruit where hairs have been removed

attachment scar of a fruit where hairs have been removed

floral heads with the hairy achenes still attached; photo by Fred Hrusa: © 2001 CDFA

floral heads with the hairy achenes still attached; photo by Fred Hrusa: © 2001 CDFA

A, fruit; B, embryo in situ; C, transection of fruit; drawing by Lynda E. Chandler

A, fruit; B, embryo in situ; C, transection of fruit; drawing by Lynda E. Chandler