BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Lolium multiflorum | Italian Ryegrass 



GENERAL BOTANICAL CHARACTERISTICS : 
Italian ryegrass is an introduced, annual or biennial, cool-season
bunchgrass.  The erect, spreading, or decumbent culms grow 50 inches
(127 cm) tall.  Spikelets are 11- to 22-flowered; lemmas are usually
awned [59].  Roots are shallow when irrigated, which has led to the
assumption that Italian ryegrass has a shallow root system.  However,
the fine, fibrous root system extends over 3 feet (1 m) deep on
nonirrigated sites [7,52,55].


RAUNKIAER LIFE FORM : 
   Therophyte


REGENERATION PROCESSES : 
Italian ryegrass regenerates by seed.  It is self-incompatible [39].
Seeds are probably dispersed by animals.  Two cultivars (`Tribune' and
`Lemtal') had higher germination rates 6 months after harvest (95
percent) than 3 weeks after harvest (50 percent), indicating some degree
of dormancy immediately after harvest [32].  Seeds germinate rapidly
without pretreatment [29].  Germination rates are high; 2-week
germination was 80 percent under summer day/night temperatures (86/62
degrees Fahrenheit [30/17 deg C]), 76 percent under spring and fall
temperatures (74/50 degrees Fahrenheit [23/10 deg C]), and 71 percent
under winter temperatures (62/39 degrees Fahrenheit [17/4 deg C]) [1].

Italian ryegrass is unlikely to form a substantial seedbank because
seeds germinate readily [50].  Thompson and Grime [60] place Italian
ryegrass in the transient seedbank category; seeds are present only for
a short time in the summer and fall.  Where high soil temperatures are
associated with intermediate soil moisture, viable seed is depleted
through germination [51].  However, seed dormancy is induced when seeds
are buried in cold, wet soil.  Dormancy in buried seed did not reach
maximum levels until 120 days after burial [51].  The longevity of
buried Italian ryegrass seed is not known.

Italian ryegrass tillers profusely [7,29].  


SITE CHARACTERISTICS : 
Italian ryegrass grows in a wide range of soil types except for
excessively drained or very poorly drained soils [25].  It requires
medium to high soil fertility in order to persist on a site [53].
Italian ryegrass is intolerant of hot, dry weather.  It can survive
short periods of flooding if well established [53].

Italian ryegrass is reported to grow at less than 3,280 (1,000 m) in
California [31], at 6,400 feet (1,350 m) in Utah, 6,500 feet (1,380 m)
in Montana, and 4,000 to 8,000 feet (1,220-2,440) in Colorado [13].


SUCCESSIONAL STATUS : 
Italian ryegrass is a shade intolerant species.  In a reciprocal
transplant study between the California annual grasslands and an
adjacent coast live oak (Quercus agrifolia) woodland, Italian ryegrass
disappeared after 1 year of shading by the oak canopy.  The canopy did
not inhibit germination, but seedling survival was poor.  Italian
ryegrass was the most shade-sensitive herbaceous species in the study
[42].  Italian ryegrass generally increased in cover with removal of
blue oak (Q. douglasii) in woodlands and savannahs in the northern
Sierra Nevada foothills [37].

In portions of the California annual grasslands, three species
frequently coexist:  wild oat (Avena fatua), soft chess (Bromus
hordeaceus), and Italian ryegrass.  Wild oat retains dominance but is
unable to exclude the other two species.  Italian ryegrass has the
smallest seeds but overcomes this disadvantage with rapid growth [24].

In the Pampean grasslands of Argentina, postagricultural succession was
observed for 5 years.  Italian ryegrass was not present the first year
and was not planted, but occurred the second year with 5.6 percent cover
and increased to 42.8 percent cover by the fifth year.  As Italian
ryegrass became more homogeneously distributed, plant diversity
decreased.  The thick litter of Italian ryegrass may have inhibited
other species [15].

In some ecosystems, Italian ryegrass is succeeded by perennial
herbaceous species and shrubs.  Italian ryegrass was initially prominent
where introduced onto sites disturbed by the 1980 eruption of Mount St.
Helens.  However, the native, perennial colonizers fireweed (Epilobium
angustifolium) and western pearlyeverlasting (Anaphalis margaritacea)
soon became dominant [26].

Coyotebrush (Baccharis pilularis) invades California annual grasslands
if grazing ceases and suppresses Italian ryegrass [34,43].  In May in
the Santa Cruz Mountains, open grasslands contained 340 grams per square
meter Italian ryegrass, but 2- to 3-year-old coyotebrush stands
contained only 2 grams per square meter, and 9-year-old coyotebrush
stands contained no Italian ryegrass [34].



SEASONAL DEVELOPMENT : 
In California, Italian ryegrass germinates with the onset of the fall
rainy season [24], generally when temperatures dip below 50 degrees
Fahrenheit (10 deg C) [10].  Growth is initially rapid, slows in the
winter, then increases again in the spring [7,24].  Spring growth does
not occur until the mean daily temperature rises above 50 degrees
Fahrenheit (10 deg C) for several days, usually in late February in
southern California.  No growth occurs until March above 2,500 feet (760
m) [10].

Although aboveground growth slows in the winter, Italian ryegrass roots
continue to grow.  In mid-January in California, roots averaged 8 inches
(20 cm) deep, and in early March roots averaged 12 inches (30 cm) deep
while seedlings were still in the two- to three-tiller stage.  By
mid-April, roots were 23 inches (58 cm) deep and most tillers had been
produced.  Italian ryegrass roots excavated in July were 56 inches (142
cm) deep [52].

Italian ryegrass begins drying in late April in California [52].  In
1960 near Berkeley, maximum Italian ryegrass biomass occurred in late
May [28].

In Colorado, anthesis begins in June and ends in July.  In Montana, it
begins in May and ends in July [13].

Related categories for Species: Lolium multiflorum | Italian Ryegrass