Italian ryegrass, Lolium multiflorum, April–Oct
perennial ryegrass, Lolium perenne

Lolium spikelets are arranged edgewise to the rachis (axis), and the first or inner
glume is suppressed except in the terminal spikelet. A branched form, a hybrid, can also be found on the Preserve. John Thomas in his Flora of the Santa Cruz Mountains writes that branched Lolium has been called "L. multiflorum var. ramosum Guss. ex Arcang" (p. 89 ). In the Manual of Grasses of North America branched lolium is included in a complex of grasses called Lolium x hybridum:

Lolium used to be included in the Triticeae [as in John Thomas], but evidence from genetics, morphology, and other studies show a close relationship to three former Festuca species included here in Schedonorus. Artificial hybrids have been produced among L. perenne, L. multiflorum, Schedonorus pratensis, and S. arundinaceus.

The Flora of North America treatment for L. multiflorum and L. perenne:

2 Plants long-lived perennials, with 2-10 florets per spikelet; lemmas unawned or with awns to 8 mm long ..... L. perenne
2' Plants annuals to short-lived perennials, with 10-22 florets per spikelet; lemmas with awns to 15 mm long, rarely unawned ..... L. multiflorum

Lolium perenne and L. multiflorum are interfertile and intergrade. Typical L. perenne differs from L. multiflorum in being a shorter, long-lived perennial with narrower leaves that are folded (rather than rolled) in the bud.

JRBP’s some 60 acres of serpentine soils is a small portion of the 3000+ acres exposed in the Bay Area (McCarten, 1993). It is a beautiful landscape of native prairie grading variously into serpentine chaparral, woodland, and oak savanna. There are no known, federal or state listed rare plants or animals associated with the Jasper Ridge serpentine, though there are some uncommon plants such as Allium peninsulare francsicanum (McNeal, 1977; 1992) and Lessingia hololeuca. The onion and the wooly-headed lessingia can be seen near the beginning of trail 5, the Lost Serpentine loop. The remaining bay checkerspot butterfly population appears to have been extinct at JRBP as of 1999 (Weiss, 1999).

The ridgetop has also not been grazed since 1960. Grazing removal has been detrimental to the native plant diversity of other sites (Weiss, 1999; Edwards, 1992, 1995; xxxx) Prevailing NW winds have resulted in less Nitrogen deposition from air pollution at JRBP than at some other Bay Area sites (Weiss, 1999). Increased N favors annual grasses by mitigating some of the harsh chemistry for plants of serpentine soils. JRBP serpentine soils had not been heavily invaded by Bromus hordeaceus, Lolium, or Avena by the early 1990s (Hobbs & Mooney, 1995). An increase of Italian ryegrass in 1998 corresponded with record El Niño rainfall (Weiss, 1999). Lolium multiflorum appears in all JRBP floras. The earliest record for Lolium growing in the serpentine is from Herb Dengler’s 1962/63 fieldnotes recently transcribed by Zoe Chandik. On May 19, 1962 he writes, evidently with reference to both Bromus hordeaceus and Lolium, “Mediterranian grass has successfully invaded the serp this year.” Springer (1938) found Italian rye grass to be “frequent along roadsides and in open fields and on openly wooded slopes near roads.” Thomas (1961) did not report Italian rye grass growing on serpentine in the Santa Cruz Mountains. McNaughton (1968) did not report Italian rye grass on serpentine. In 1990 the third revised edition of the Jasper Ridge Docent Handbook still identified only soft chess from among the Preserve’s naturalized grasses growing on serpentine. Armstrong and Huenneke (1993) documented Lolium was common in serpentine by 1985-86 and that it was negatively effected by drought. In 2001 and 2002 Lolium accounted for 32% and 20%, respectively, cover of Stuart Weiss’ JRBP serpentine transects (Weiss, 2002). In Spring 2006 the herbarium crew assisted in two relevant-to-this-issue surveys, a repeat of the Armstrong and Huenneke transect; and the vegetation component of a small mammal inventory. It is our impression that Lolium may approach a frequency of 80% to 90% in these serpentine quadrats. Hobbs et al. (2007, p.554-45) data shows lower coverage and frequency of Lolium for 1983-2003. The herbarium crew has not examined Hobbs' 50 x 50 m quadrats. Also see CNPS Vegetation Rapid Assessment Field Form JASP0001 3/25/2008.

Weiss writes:

The invasive grasses that have dramatically changed California’s grasslands are poised to dominate the last refugia for the native grassland flora and fauna, given the chance. That chance is provided by smog-induced fertilization, but only with the additional land-use change of removing grazing . . . It is ironic that grazing, which has contributed so greatly to the transformation of California’s native grasslands, may prove necessary for their maintenance . . .

—Weiss, 1999, p. 1485

Exhaust from cars, about 110,000 vehicles a day on Highway 101, along with other urban sources, annually deposit 15 to 20 pounds of nitrogen per acre on Coyote Ridge south and east of JRBP, according to Weiss's monitoring equipment.

Some of the nitrogen is absorbed by living plants, while small particles of the pollutant stick to plants and the ground and are washed into the soil by rain. By contrast, pollution from power plants and vehicles each year deposits just four to five pounds of nitrogen per acre on Jasper Ridge, a Stanford University biological reserve half an hour away. http://www.washingtonpost.com/wp-dyn/content/article/2006/05/21/AR2006052100725.html

However, even as smog-derived Nitrogen deposition is not as great at JRBP (upwind from most pollution sources) as it is for other serpentine grasslands that are downwind, the spread of Lolium shows other factors can and will contribute to annual grass invasions, and that once introduced, some naturalized plants will have the genetic adaptability to persist on serpentine and other nutrient-poor soils.

Name: Latin name for ryegrass | multi-flowered.