Texas Gardening: Texas Native Plant Pictures by color ( Yellow ), 1 by htop

htop wrote:
Tocalote, Malta Thistle, Maltese Star-thistle, Cockspur Thistle, Yellow Star-thistle, Napa Thistle (Centaurea melitensis), Asteraceae Family, naturalized, annual/biennial, invasive

Malta thistle, Maltese star-thistle, cockspur thistle, yellow star-thistle, Napa thistle (Centaurea melitensis) is an introduced invasive winter annual plant. It is difficult to distinguish between Malta star-thistle and yellow star-thistle (Centaurea solstitialis) until they flower. Both have bright yellow thistle-like flowers with prominent spines emanating from the flower base in a star-like arrangement at the base of the flower head. The spines on yellow star-thistle flowers are ¾ to1 inch long, yellow, very stiff and pointed like a cactus spine. Malta star-thistle has tan spines that are not as stiff and shorter (3/8 inch). Malta star-thistle bracts below the heads have short often reddish or brownish spines; whereas, yellow star-thistle bracts have yellow spines. Yellow-star thistle blooms have discoid heads that are about one inch in diameter. Malta star-thistle blooms stand 1/2 to 5/8 inch tall. Malta-star thistle blooms May-December with yellow star-thistle blooming April-September.

For more characteristis that differientiate these 2 plants, see its entry in the PlantFiles (link below).

Distribution:

http://plants.usda.gov/java/county?state_name=Texas&statefip...

For more information, see its entry in the PlantFiles:
http://davesgarden.com/pf/go/127519/index.html

The bloom is a thistle-like flower about 3/8" to 1/2" wide. Its bracts have spines. Shown in April (blooms in background are on a different plant) ...