Maltese Star-Thistle

Centaurea melitensis

Centaurea melitensis photo © by Michael Plagens

Photographed at Bumble Bee, Yavapai Co., Arizona, USA on 14 June 2008.

ANNUAL: Herbaceous weed of disturbed ground. Plants may grow to over a meter in height under favorable soil and water conditions thus producing thousands of seeds.

ARMED. The phyllaries subtending the flower heads terminate in sharp, 10 mm-long spines. Smaller spines branch out from the base of the central spine.

FLOWERS: Many spiky, bright yellow disc flowers arranged into a compact head. The phyllaries around the head bear the spines and are usually cob-webby. Flowers blooming mid to late spring.

LEAVES: Leaves are narrow, almost linear above, and alternate on stem. Lower leaves may have additional elongate lobes.

RANGE: Malta, of course, is an island in the Mediterranean and this weed is not native to the Sonoran Desert; its origin is southern Europe. Accidentally introduced and now invasive in disturbed habitats along washes and riparian streams across much of the western United States.

FRUIT: Many seeds develop within each head. They are tan-colored with fine, white bristles at top.

Asteraceae -- Sunflower Family

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More Information:

Sonoran Desert Field Guide
Sonoran Desert Places
Sonoran Desert Naturalist Home Page


Copyright Michael J. Plagens, page created 7 Nov. 2008,
updated 2 March 2017.