Lolium multiflorum Lam. (1779)

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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].

I, II, III, IV, V, RM, VI, VII, VIII, IX, X, XII, Juan Fernandez

Fl. & Fr. Per.: June-August.

Distribution: Pakistan (Baluchistan & N. W. F. P.); Central and southern Europe, Northwest Africa and Southwest Asia; introduced into most temperate countries.