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Yavapai County Native & Naturalized Plants

Centaurea melitensis - Maltese star-thistle

Other Common Names: Malta starthistle, spotted knapweed
Plant Form: Forb

Family: Asteraceae

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Forb Plant Description

Origin: Introduced   Life Cycle: Biennial or annual   Similar Species: Centaurea solstitialis
General Desc: The winged stem is stiff, openly branched and covered with cottony short soft hairs.
Identification notes: Flower heads of 1/2 to 1 inch, usually on stems, not concealed by foliar bracts, spine tipped phyllaries (bracts) , spines under 1/2 inch long and phyllary appendages that are spiny fringed distinguish this from other Centaurea sp.
Height: 2 to 3 feet


Habitat Description: This starthistle prefers disturbed and open areas, including grasslands, woodlands, agricultural fields, and roadsides.
Plant Communities: Desert Scrub, Interior Chaparral, Semidesert Grasslands, Pinyon Juniper Woodland, Montane Conifer Forest, Riparian, Disturbed Areas
Elevation: Below 7200 feet

Flower Characteristics

Color: Yellow     Shape: Daisy or dandelion-like not in clusters     Tubular: N     Flowering Period: Apr - Jul
Description: Flower heads are surrounded by sharp, straw-colored 3/4 inch thorns. One to few flower heads at branch tips are borne singly or in open arrays.

Leaf and Stem Characteristics

Leaf Color: Gray-green     Leaf Type: Simple     Leaf Shape: Narrow     Leaf Margin: Lobed     Leaf Attachment: Basal and alternate     Leaves Clasp: N
Hairs: Leaves and stems     Spines: N
Leaf Description: Basal leaves are deeply lobed, while the upper leaves are entire and sharply pointed. Leaves are resin dotted. Margins of the leaves can be smooth, toothed, or wavy depending on the individual plant and its maturity.

Fruit and Seed Characteristics

Fruit Color: Light brown   
Fruit Type: Achene
Seed Notes: Seed production is highly variable from year to year and plant to plant.

  Arizona Cooperative Extension
Yavapai County
840 Rodeo Dr #C
Prescott, AZ 86305
(928) 445-6590
Version 7.0  
Last Updated: May 10, 2017  
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