Giant Wild Rye

Elymus condensatus

Giant wild rye often towers above surrounding begetation
East Basin, south side | July 2010

Grass is what holds the earth together.
Grass made it possible for the human race to abandon his cave life and follow herds.
Civilization was based on grass. Everywhere in the world.” P. Hansen 493


Giant wild rye (Elymus condensatus) is our largest native grass. With leaves three to four feet in length and flower stalks to eight feet or more, this perennial grass often towers above the surrounding shrubs.

Grass flowers, or florets, are clustered along the top of the flowering stalk, but they lack the colorful petals of typical flowers. The pollen-bearing anthers can sometimes be seen dangling out of the florets, from where they can more effectively shed their pollen into the wind.

Several Native American tribes made arrows from the long, strong flowering stalks, straightening them with heated stones.

Other Common Names:

Giant reed

Description 2,4,11

Giant wild rye is a large, coarse, perennial grass.  With flower stalks it may reach eight feet or more in height.  It often grows in dense clumps, from short rhizomes. Leaves are mostly upright along the main stem; they are usually less than 1/1/4 inches (3.3 cm) wide and may reach 3 1/2 feet (40 cm) in length feet in length. The base of the blade clasps the stem.

The flower structure of giant wild rye, like that of all grasses, is highly specialized and is described with a technical vocabulary. Simple, illustrated descriptions of grass structure are available on line.130 Flowers (florets) lack petals and sepals. Instead, the developing reproductive organs are protected by two specialized bracts, the lemma below and the palea above. There are three stamens with large yellowish anthers that dangle from the floret on long thread-like filaments . There is one pistil with two (sometimes three) styles with white, feathery stigmas.

One to seven florets are arranged in short spikelets; each spikelet is subtended by two linear bracts (glumes) each often extended into a stiff hair-like point. Spikelets, in turn, occur in narrow, dense clusters along the terminal portion of the stem, Flowering clusters can be 15 inches (40 cm) long. The main bloom time is May through August.468

Each flower produces a single seed that develops and disperses within the lemma and palea.


grass blade wraps the stem

Grass blade wraps stem | East Basin, south side | June 2019

flowers lack petals

florets with anthers dangling from slim filaments, line points to feathery stigma | East Basin, south side | June 2010

dried grass seeds

One spikelet with several mature florets | Stonebridge Mesa | July 2019

Distribution 7,11,34,89

Giant wild rye is native to California where it is concentrated in coastal and southern California from the foothills west, below 6000 feet (1900 m). It is most often reported from dry areas in coastal sage scrub, chaparral and open woodlands, but it is also found in scattered locations elsewhere throughout the state and along the coast of Baja California.

In the Reserve, naturally occurring plants are associated with seeps and drainage areas, especially near the base of the north facing slopes of Central and East Basins. Plants have been used in our sage scrub restoration areas where they seem to have become established.

Classification 310,493,495

Giant wild rye is a perennial monocot in the grass family (Poaceae, formerly Gramineae). The grass family is one of the largest plant families and is considered to be the most economically important, containing such food crops as wheat, rice, oats corn and sugar cane. It has been estimated that 70% of all crops are grasses.41

Grasses have unique terminology.130 They are characterized by their cylindrical stems (culms), which are generally hollow or pith-filled with solid joints (nodes). Leaves (blades) are flat, alternating along the stem, one leaf per node; leaf bases wrap the stem forming the leaf sheaths; at the junction lies a membrane called a ligule. Flowers (florets) lack typical petals and sepals. Instead, the reproductive organs develop with two modified bracts (lemma and palea). Florets are arranged into spikelets, subtended by two additional bracts (glumes), and spikelets may be further organized into spikes. In agriculture, after harvesting, grains are “winnowed” to remove the “chaff”. Chaff is the collection of bracts that enclose the seed.310

There are currently hundreds of species of Elymus recognized.2 These are distinguished by characteristics of the spikelets, especially the glumes and lemmas, and by characteristics of the leaves, especially the sheaths and ligules.2 

While giant wild rye is technically distinguished by floral and leaf traits, in the Reserve it is often recognized by its height, which is comparable only to the non-native pampas grass and giant reed (Arundo donax). Giant wild rye soars above our other native grasses.

Alternate Scientific Names:

Leymus condensatus

Jepson eFlora Taxon Page
tall stems of giant wild rye

East Basin, south side | July 2010

stem of giant wild rye

Like other grasses, stem is hollow | East Basin, south side | July 2017

brown gtrass spoke with seeds

Mature spike | Stonebridge Mesa | Aug. 2019

Ecology 493

Grasses and their herbivores are highly adapted to each other. In the fossil record. Grasses and grazers had similar periods of expansion and diversification in the mid-Miocene,495  leading some to postulate co-evolution of the two groups.

A grass has its major growth points at the base of the plant; leaves elongate from the base outward, so repeated grazing does not damage the plant.41,310,494 Grasses evolved leaves that are impregnated with siliceous particles (phytoliths) that make them tough and are thought to deter grazers.498  However, many grazers evolved deep-crowned cheek teeth with enamel patterns adapted for chewing the hard, phytolith-impregnated leaves. The hoofed grazers evolved long legs with solid toes, appropriate for long-distance running through low, open grasslands. Many grasses evolved deep rhizomes that protect the plant from trampling.

Was this true co-evolution, in which small changes in grasses stimulated small changes in grazers, which stimulated small changes in grasses, and so on, back and forth through time? 497,498  Or did grasses primarily evolve in response to climatic changes, 495,498  with grazers adapting to this new food source? Or, did, perhaps, grazer evolution lead the way, with grasses developing defensive, protective measures?498 While the remarkable co-adaptation we see today is accepted, the sequence of driving forces behind the evolution of grasses and grazers is contentious.495

small clump of giant wild rye

East Basin, south side | April 2016

Portion of a blooming flower spike

Portion of a blooming spike with dangling anthers | Stonebridge Mesa | July 2019

grass stalk at end of bloom

Stonebridge Mesa | June 2019

Human Uses 15,17,75

Prior to Spanish settlement, the only reed available to the local Indians was giant wild rye, which was used as the mainshaft of their small, two foot (about 60 cm) light weight arrows for birds and small mammals. The stem was allowed to dry and then straightened in a special grooved straightening stone. The stone was heated and the shaft turned continually in the groove until smooth and straight. The nodes were smoothed with a knife. A foreshaft of toyon or California sagebrush or chamise was inserted into the hollow at the lower end and held with tar or pine pitch or resin and secured with sinew. Feathers for fletching were usually trimmed hawk feathers. The foreshaft was pointed or separate points were inserted.

There are reports of many other uses of giant wild rye by the Chumash, from thatching to medicine to drinking straws and knives.15

The missionaries brought two other reeds: Phragmites  sp. and Arundo donax. Together with the giant wild rye, these were collectively called giant reed or carrizo by the Spanish and often used interchangeably.

giant wild rye in sage scrub vegetation

East Basin, south side | June 2010

Giant wild rye often towers above surrounding shrubs

East Basin, south side | July 2010

giant wild rye going to seed

Stonebridge Mesa | August 2019

Interesting Facts 291

The close relationship between grasses and their grazers is reflected in the two nouns. The Old English word graes gave rise to the modern counterpart, grass, and also to grasian (to feed on grass), which time and use further modified to graze.

Giant wild rye growsing along trail

East Basin, south side | June 2010

portion of blooming spike

Portion of blooming spike with anthers | Stonebridge Mesa | June 2017

Flowering stem of giant wild rye

Florets are arranged into spikelets that are arranged into a terminal spike| Central Basin, south side | June 2016

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