Yellow Starthistle


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Noxious Weed Alert
Chaves Soil & Water Conservation District
1011 S. Atkinson
Roswell, NM 88203
Noxious Weed Coordinator
575-622-8746 ext 100




New plants start from seeds.
Plants spread rapidly, form dense stands,
and will push out desirable plants. TOXIC
to horses! Can cause “Chewing Disease” which is a neurological disorder of the brain.

Yellow Starthistle is a noxious erect winter Yellow starthistle in field near Hondo river
annual or sometimes biennial with spiny yellow-
flowered heads mostly to 3-5 feet tall. Plants are
highly competitive and typically develop dense, impenetrable stands that displace desirable vegetation in natural areas, rangelands, and other places. Yellow starthistle is considered one of the most serious rangeland weeds in the northwestern U.S. It has spread rapidly since its introduction into California around 1850. In 1995, it was estimated to infest 10-12 million acres in the state. It has started to spread rapidly outward from California to other states. Seeds often contaminate grains and forage crops lowering the value and quality of harvests, and is spread by shipments leaving the area. Seedlings: cotyledons 6-9 mm, 3-5 mm wide. Later rosette leaves typically deeply lobed to midrib, appear ruffled. Surfaces densely covered with fine cottony hairs with stiff thick hairs and leaf surfaces. Mature plants: Stems stiff, openly branched from near or above the base or sometimes not branched in very small plants. Stem leaves alternate, mostly linear or narrowly oblong to oblanceolate. Margins smooth , toothed, or wavy. Leaf bases extend down the stems and give stems a winged appearance. Flowers: Heads are ovoid, spiny, and solitary on stem tips, and consist of numerous yellow disk flowers. Plants usually senesce in late summer or fall. Heads shed the central spines, but tightly retain a ball of dense fuzzy gray hairs (chaff) on the receptacle. Often a dense layer of thatch develops on heavily infested sites.


STOP THE SPREAD OF SEEDS, and each year you’ll have a lot fewer plants. It will take 3-5 years to completely eradicate. Grazing, mowing, burning, and cultivation, can prevent seed production and control infestations when employed over a period of 2-3 years or more, depending on the degree of infestation and other factors. These methods must be properly timed to be effective. High-intensity short-duration grazing by sheep, goats or cattle should be implemented during the period when plants have developed flowering stems, but not spiny heads. Mowing is most effective when plants are cut below the height of the lowest branches and 2-5% of the total population of seed heads is in bloom. Burning can provide control if implemented after plants have dried, but before seed is produced. Repeated shallow cultivation
throughout the germination period and prior to seed production can control plants in crop fields. Herbicide applications may be needed for large infestations.

Works well on plants with lots of seeds
Will permanently kill annuals and biennials

CLIP off ALL the flowers/seed heads BEFORE seeds start spreading. Put ALL the flowers/seed heads in double plastic bags, and close them securely. Remove them from the weed site because the heads will continue to mature. Don’t just dump them anywhere, you’ll spread them! Put them in a black plastic bag for a couple of months until the seeds are not viable, then dispose of them in a county dumpster.
FLIP so the plant won’t re-grow new flowers and seeds.
Yellow starthistle along a ditch Cut the plant about ½ inch deep below the soil’s surface.
Can leave the plant lying on the ground or dispose it.
Be sure there are no little flowers or heads that will mature.
Spines can make clipping difficult

We can help: GIVE US A CALL
– Identify unknown plants 575-622-8746
– Determine control methods
– Demonstrate proper methods
– Get you started on the right path
We can:
– Provide herbicides
– Provide classes and information on obtaining chemical use licenses.

(Thanks to the Cuba Soil and Water Conservation District for allowing us to use their weed alert format.)

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