Common crupina or Bearded
creeper [Crupina vulgaris Cass.][CJNVU][CDFA List: A][Federal Noxious
Weed] Photographs Map
SYNONYMS:bearded creeper, Centaurea crupina L., Serratula
crupina (L.) Vill.
DESCRIPTION:Winter annual, with erect, openly branched flowering
stems to 0.6(1) m tall at maturity. Most germination occurs after the first
significant rains of fall/early winter, but germination can continue throughout
the rainy season. Fall germinating plants exist as basal rosettes until flowering
stems bolt in spring. Rosette leaves whither as flowering commences in late
spring/early summer. Plants adapt to many environmental conditions, are highly
competitive for water and nutrients, and often produces solid stands.
Introduced from southern Europe.
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SEEDLINGS:Cotyledons oblong, 1-2.5 cm long, and fleshy.
Midvein and margins often purplish-red. First rosette leaves entire with toothed
margins. Subsequent leaves increasingly lobed.
PLANT:Rosette leaves oblong to obovate,
to 8 cm long, sessile or petioled, covered with short stiff hairs, and deeply
once-pinnately divided with lobes narrow and opposing.
Stem leaves alternate, reduced near stem tops, and pinnately
(sometimes bipinnately) divided with narrow lobing. Rosette
and stem leaf margins appear spiny-toothed with stiff hairs barbed
at the tips (glochidiate). Stems longitudinally ridged.
and UNDERGROUND STRUCTURES:Dense, fibrous
FLOWERS:June until soil moisture is depleted. Flower heads on stalks
1-3 cm long, consist of 1-2 central fertile disc flowers and
2-4 outer sterile disc flowers. Corollas are slender purple tubes
with linear lobes, together ~ 14 mm long. Phyllaries
lanceolate, in several overlapping series, and as a unit, 8-20 mm long
and slender urn-shaped. Receptacle with flattened, scale-like chaffy
and SEEDS:Fertile achene nearly cylindric,
3-6 mm long, 1.5-3.5 mm wide, base rounded, appex +/- fat-topped, black-brown,
+/- covered with minute, lustrous golden-brown scales that rub off easily.
Pappus bristles black-brown, glossy, stiff, radiate outwards at a 90º
angle from the achene axis in 2 unequal series. Outer bristles
inconspicuous, scale-like, flattened, to ~ 1 mm long.
Inner bristles stiff, minutely barbed, to ~ 10 mm long.
Above the bristles is a +/- erect crown of flattened scales ~ 1 mm long.
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heads remaining on old stems can aid with species identification. Refer to
the Flower Head Comparison of White, Pink, or Purple-flowered
Centaurea and Related Species Table for comparison.
HABITAT:Grassy sites, rangelands, forested areas, and roadsides. Adaptable
to many moisture and temperature regimes and soil tupes.
DISTRIBUTION:Uncommon. Modoc Plateau (sc Modoc Co.); southern North Coast
Ranges (ce Sonoma Co.); to 250 m (850 ft). Also Idaho, Oregon, and Washington;
to 1000 m (3200 ft).
PROPAGATION/PHENOLOGY:Reproduces by seed. Flower heads often disperse as a
unit. Seeds (achenes) fall near the parent plant or disperse to greater distances
with rodents, livestock, game birds, human activity, and by floating on water.
Seeds typically do not disperse beyond 1.5 m from the parent plant with wind
or 90 m (300 ft) on the hooves of livestock. Seed can survive ingestion by
most animals, except sheep. Plants produce 1(2) achenes per flower head and
about 130 achenes per averaged size plant. About 85% of seeds produced germinate
the following fall. Seeds germinate under a wide range of temperatures and
can remain viable for up to 3 years under field conditions. Plants
are grazed only when more suitable forage is lacking.
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cattle and horses for at least 6 days after foraging on rangeland infested
with flowering plants can help prevent the introduction of common crupina
to non-infested sites.
SPECIES:Several knapweeds in the
genus Centaurea and Russian knapweed [Acroptilon repens
(L.) DC.] superficially resemble common crupina. Unlike common crupina,
the knapweeds have flower receptacles with bristles and leaf margins
without bristly, barb-tipped hairs. Phyllary and achene
characteristics are important in distinguishing these species. Refer
to the Flower Head Comparison of White, Pink, or Purple-flowered
Centaurea and Related Species Table for comparison.
Prevention: Common crupina
is an aggressive invader from the same botanical tribe (Cynareae) as the knapweeds
and yellow starthistle. It is an unpalatable forage for cattle and forms dense,
monocultures in disturbed rangeland, canyon grassland, and waste areas. Crupina
is adapted to a wide range of environmental conditions and will likely increase
unless preventative measures are utilized. Since seed are the only reproductive
mechanism and are relatively short lived (less than three years), the probability
of eradication is higher than some other noxious weeds. Therefore, the prevention
of new plant establishment and seed production is critical. Crupina flowers
and produces seed throughout the summer as long as adequate soil moisture
is available. Natural seed dispersal occurs by wind and rodents for shorter
distances, and by water and in the hair of deer or cattle for longer distances.
Viable seed may also pass through the digestive system of cattle, horses,
deer and chinese pheasants, but not sheep. Therefore, horses and cattle should
be removed from infested areas to avoid overgrazing of desirable species and
possible seed dissemination. Crupina may be found in some pastures and hay
producing areas. Therefore, use certified weed free hay for winter feed and
quarantine cattle in holding pens if animals have come from crupina infested
Mechanical: Mechanical control
may be limited on steep slopes or rugged range areas. However, hand pulling,
hoeing, or tillage before flowering will be effective for controlling small
infestations. Infestations should be checked every two to four weeks in the
spring for newly emerged plants. There is little information available on
using mowing as a control strategy. However, it is not recommended after plants
have begun producing seed due to the likelihood of increased dissemination.
Biological: There are currently no available insect or pathogenic biocontrol
agents for use on common crupina. Most grazing animals will avoid it, unless
no other plants are available. This will result in natural selection for crupina.
Therefore, maintaining healthy, competitive grasses, and minimizing overuse
is the best deterrent to invasion by crupina.
Chemical: Since other control
strategies are limited, herbicides may be the most effective means for eradicating
larger infestations of common crupina. However, there are few herbicides currently
labeled for use in California. Tank mixes of dicamba (0.5 lb ae/A) + 2,4-D
(1.0 lb ae/A) applied in the fall or spring will provide season long control.
Retreatment may be necessary for two to tree years to ensure seedbank depletion.
These herbicides will injure or kill any other susceptible broadleaves they
contact. Later spring applications may reduce control variability, but may
increase the risk of injury to perennial forbes or shrubs due to volatilization.
Spring applications of gyphosate (1.0 lb ae/A) will also provide season long
control but will kill or injure any other vegetation present. Sequential fall
and spring applications of clopyralid (0.13 lb ae/A) or triclopyr (.25 lb
ae/A) also provide >95 % control. Clopyralid (Transline)will injure legumes
and triclopyr will injure or kill other broadleaves. Picloram (0.5 lb ae/A),
which is not labeled in California, will effectively control common crupina
for up to two years with one application.
Integrated management: Integrated
management is very important for improving the quality of infested areas.
Eradication of crupina on poor areas without revegetation strategies will
likely result in colonization of the area by other invasive annuals, such
as downy brome (Bromus tectorum). Therefore, reseeding perennial grasses in
the fall or spring is important for the long term health and productivity
of the land.