General: Annual herb from the Asteraceae family. Related to knapweeds.
Height: 0.2 - 1.2 meters
Flowers: Discoid (resembling a disc), usually blue, sometimes purple, pink, or white. Solitary, at the end of a branched stem. Peripheral flowers of the disc head are bell-shaped with 5 enlarged lobes. Central flowers of the disc head are a few mms shorter. Involucral bracts egg-shaped, grooved, with a darkened, tattered fringe at the tips.
Leaves/Stems: Stems grey-green, erect, branched, & loosely hairy. Basal leaves linear to lanceolate (lance-shaped), with sparse teeth & white-wooly below, soon deciduous (falling off). Stem leaves similar, reduced, & thinner upwards.
Perennial Cornflower (Centaurea montana) - also invasive and part of the knapweed family; has thinner & fewer ray flowers & thicker foliage.
Chicory (Cichorium intybus) - also invasive; the ray flowers (which look like petals) are rectangular shaped with frayed edges.
Cupid’s Dart (Catananche caerulea)– non-invasive garden plant; ray flowers are rectangular-shaped with frayed edges.
Showy Aster (Eurybia conspicua) - native; flowers look very different, similar to a daisy with yellow center & blue/violet ray flowers.
Image Link: Showy Aster, E-Flora
Where did it come from? Introduced from the Mediterranean region; an escaped garden ornamental.
Where does it grow here? Common along roadsides & in fields. Prefers dry, disturbed areas. Can grow in both the lowlands and the mountains.
Reproduction: Reproduces by seed. Plants produce many seeds, which germinate quickly so that the plant spreads aggressively.
When does it grow, flower & seed? Flowers May – July.
Spreads By: Spread by intentional planting as a garden ornamental. Often found in wildflower seed mixes. Also, often a seed contaminant in crop seeds. Further spready by wind, water, & birds.
Plant Type: Annual herb