Inula britannica

Name and classification

Inula britannica L.
(=Inula japonica Thunb., Conyza britannica (L.) Moris ex Rupr.)
Family Asteraceae, Tribe Inuleae

Common names

meadow fleabane, British yellowhead

Disseminule

fruit

Description

Fruit an achene, narrowly obovate to oblong, 1–2 mm long, 0.3–0.5 mm diameter; cross-section star-shaped; surface longitudinally fluted (ca. 8 ribs), pilose, reddish-brown. Attachment scar basal, roundish, indistinct. Pappus of 20+ barbellate bristles, cream-colored to reddish golden-brown, measuring 4–6 mm long, sometimes broken but not detached at their bases, +/– persistent. Style base roundish, +/– flanged. Embryo spatulate; endosperm absent.

Identification considerations

Other species of Inula differ by having a distinct donut-shaped carpopodium at the base of the achene.

Distribution

native to Europe and temperate Asia

Over the past century, it has been introduced to Canada and the United States, including Maryland, Michigan, Minnesota, New York and Oregon. Currently, in the U.S., it is only known to occur in Michigan.

Habitat

wet habitats at low altitudes, including river and stream margins, marshes, ditches, wet grassland, and wet woods

General information

Inula britannica is a herbaceous perennial standing 15–75 cm tall. It reproduces naturally by the dispersal of its wind-borne fruits and spread of its rhizomes. As a weed, its international dispersal occurs primarily as a result of the ornamental bulb trade. The plants infest bulb farms in The Netherlands; when the bulbs are harvested and shipped abroad, they may contain bits of Inula rhizomes lodged between the scales of the bulbs. When mixed in with hosta rootstock, the Inula roots are recognized as being light white and smooth, while the hosta roots are thicker and covered with small raised bumps.

achene with pappus

achene with pappus

achene, detail

achene, detail

achene, detail

achene, detail

apex showing stylar remains

apex showing stylar remains

base showing attachment scar

base showing attachment scar

herbarium specimen of plant

herbarium specimen of plant