Yellow Starthistle
Family Asteraceae
Centaura solstitalis
Designation/Status
Arizona Noxious Weed List -
Prohibited
Federal Noxious Weed List – Not Listed
Origins
Native to the Mediterranean
region of Europe.
Plant Characteristics
Life Cycle: A single plant has the
potential to produce up to 150,000 seeds. There are two types of
seeds produced, those with parachute-like plumes and those without
plumes. The majority of seeds produced are plumed and dispersed
at maturity between the months of November and February.
Approximately 90% of seeds produced will fall within two feet of
the parent plant.
Visual
Appearance: Bright yellow flowers on the end of short
branches. The flower heads consist of many individual flowers and
bracts. Bracts are armed with a stout, straw colored spine 1 to 2
inches long. Spines radiate from the flower head in a star shape.
Yellow Starthistles produce a rosette of leaves that lie close to
the ground. These basal leaves are deeply lobed, and generally
less than 2 inches wide and 8 inches long. Stems range from
4 inches to 5 feet tall, depending on the environmental
conditions. Stem leaves are entire, linear, and have thin
woolly hairs that persist through the growing season.
Habitat
Rangeland, pastures, roadsides, and wastelands.
Control Measures
Mechanical and Cultural: Because Yellow Starthistle is
a winter annual, hand pulling can be quite effective. This is
especially effective on new introductions. Care should be taken
not to spread seeds when hand-pulling. Placing the pulled plants
in a garbage bag is a good measure to prevent seed spread. On
large scale infestations, tilling so that the roots are separated
below the soil surface should provide complete control of these
plants.
Biological:
In Arizona the weevil Eustenopus villosus is available and
effective at feeding on flower heads and flower buds.
Chemical: Effective
herbicides include: 2,4-D, Clopyralid, and Glyphosate. Chemical
control is an appropriate tool to use: 1) on large infestations,
especially when desirable plants are abundant in the under story;
2) in highly productive soils; and 3) around the perimeter of
infestations to contain their spread. Picloram may be applied to
seedlings or rosettes with some effect.
Other Points of Interest
Seeds of the species are believed to have arrived in North America
in Alfalfa seeds shipped to California in the middle to late
1800s.
