Malta Starthistle (Tocalote, Napa Thistle)
Family Asteraceae
Centaura melitensis
Designation/Status
Arizona Noxious Weed List – Not
Listed
Federal Noxious Weed List – Not
Listed
Origins
Native to regions in
Southern Europe.
Plant Characteristics
Life Cycle: Winter annuals with
a simple tap root. Flowers can be seen from April to September.
Seed heads typically produce between 30-80 seed heads
Visual Appearance: Grows 1 to 2
feet tall. The plant is short-stalked, with lobed leaves that form
a rosette. Upper leaves are narrow, entire, and come to a point
attached directly to the stem. Yellow-flowered heads develop with
floral bracts. Floral bracts are tipped with slender spreading
spines up to 0.375 inch long and tinged with purple or brown. The
main spine has smaller spines branching from it at the base and
near the tip. Seeds are achene's ~2-3 mm long, finely
pubescent, grayish to +/- tan, usually with slightly darker
stripes.
Habitat
Occasionally found in
alfalfa fields, grain fields, pastures, the banks of irrigation
ditches roadsides, and waste places, in Apache, Yavapai, Maricopa,
Pinal, Graham, Pima, and Cochise counties; mostly below 4,000
feet, but sometimes to 7,000 feet elevation
Control
Measures
Mechanical and Cultural: grazing, mowing, and burning
can prevent seed production and control infestations when used
over a period of 2-3 years or more. These methods must be
properly timed to be effective. Mowing is most effective when
plants are cut of the lowest branches and 2-5% of the total
population of the seed heads is in bloom. Mowing too early can
result in high seed production.
Biological: None
Chemical: All starthistles are highly susceptible to
the herbicide cloppyralid
Other Points of interest
Introduced in America in the
late 1700s
