Grasses are among the most important plant species on the planet. They are found in a variety of ecosystems, including grasslands, savannas, prairies, and wetlands, and they play a critical role in maintaining the health and balance of these ecosystems. Grasses are important habitat creators, providing shelter and food for a wide range of animals. Many species of birds, including grassland birds and waterfowl, depend on grasses for nesting and foraging. Grasses also provide cover and shelter for many species of insects, which are important pollinators and decomposers. By creating diverse grassland habitats, we can support a wide range of animal species and help to maintain biodiversity. Grasses are incredibly powerful plants with a wide range of benefits for the ecosystem. They play critical roles in soil stabilization, carbon sequestration, habitat creation, nutrient cycling, water regulation, erosion control, and livestock feed. I thought I would explore some of the important grasses in the Mohave desert including riparian areas such as springs.
Neither grasses, sedges, nor rushes have colorful, large, or showy flowers. All are wind pollinated and so do not need bright petals or nectar to attract animal pollinators or they propagate by rhizomes or sod. For this reason, the flowers are simplified and usually small in size. Grasses have long leaves or blades, straight thin roots, a rounded (often hollow) stem (or culm), and a flowering spike. Lots of people may not realise that the top region of a grass plant happens to be the plant’s flowers and seeds. It becomes obvious when you think about a grass like wheat, but other species might fall under the radar. Grasses adapt to the environment. While most plants grow from the top, grasses grow from the bottom. This means that they will not die off due to grazing because they replace lost parts by “pushing up” the surviving parts that have not been eaten by animals.
In grasses, awns typically extend from the lemmas of the florets. This often makes the hairy appearance of the grass synflorescence. Awns may be long (several centimeters) or short, straight or curved, single or multiple per floret. Some biological genera are named after their awns, such as the three-awns (Aristida as seen below).
A spike is an unbranched, indeterminate inflorescence, similar to a raceme, but bearing sessile flowers (sessile flowers are attached directly, without stalks). Examples occur on Malabar nut (Justicia adhatoda) and chaff flowers (genus Achyranthes). A spikelet can refer to a small spike, although it primarily refers to the ultimate flower cluster unit in grasses (family Poaceae) and sedges (family Cyperaceae), in which case the stalk supporting the cluster becomes the pedicel. A true spikelet comprises one or more florets enclosed by two glumes (sterile bracts), with flowers and glumes arranged in two opposite rows along the spikelet. Examples occur on rice (species Oryza sativa) and wheat (genus Triticum), both grasses.
Purple Three-awn Grass
This is a perennial bunchgrass, growing erect to under 3 feet in height and the flower glumes often assumes a light brown to reddish-purple color. There are several varieties with overlapping geographical ranges. This is not considered to be a good graze for livestock because the awns are sharp and the protein content of the grass is low. This grass is fairly widespread and can be found across the western two thirds of the United States, much of southern Canada and parts of northern Mexico. It is most abundant on the plains.
Bottlebrush Squirreltail Grass
Elymus elymoides is a perennial bunch grass growing to around 0.5 metres (20 in) in height. Its erect solid stems have flat or rolled leaf blades. The inflorescence is up to 6 inches long and somewhat stiff and erect, with spikelets 1/2-1 inch (1-2 cm) long not counting the awn, which may be 1 inch (9 cm) long and sticks straight out at maturity, making the inflorescence look like a bottlebrush, and aiding wind dispersal of the seeds. In contrast, the early-season spike is compact and reddish.
Distichlis spicata is a hardy perennial with rhizomes and sometimes stolons. It is an erect grass which occasionally approaches half a meter in height but is generally shorter. The solid, stiff stems have narrow leaves up to 10 centimeters in length, which may be crusted with salt in saline environments. This species is dioecious, meaning the male flowers and female flowers grow on separate individuals. The pistillate inflorescence may be up to 8 centimeters long, with green or purple-tinted spikelets. The staminate flowers look quite similar, thinner but larger overall and denser. The flower parts of both sex may be bright pinkish-purple.
Dasyochloa is a monotypic genus containing the single species Dasyochloa pulchella (formerly Erioneuron pulchellum), known as desert fluff-grass or low woollygrass, a densely tufted perennial grass found in the deserts of the southwestern United States. It is native to the Southwestern United States, California, and northern to central Mexico, where it grows in dry regions such as deserts. The leaves produce soft, cob-webby hairs that dissolve in water, after summer rains. The hairs are typically not present in spring. These are actually hairlike strands of excreted and evaporated mineral salts. Numerous hairless, wiry, stems are 2–5 inches (5–13 cm) tall. Inflorescence. The hairy inflorescence is a spikelet on the end of the stem, surrounded by a bundle of bractlike leaves, and is 1/4” to 1/2” long. The spikelets which are pale in color, sometimes striped with red, purple, or green. It blooms from February to May.
Big Galleta Bunch Grass
Pleuraphis rigida (syn. Hilaria rigida) is a species of grass known by the common name big galleta. It is native to the southwestern United States and northern Mexico, where it is widespread in scrub, woodland, grassland, and plateau habitat. It is tolerant of arid environments such as desert floors, and it is the dominant grass in some desert scrub regions. It is a bushy, clumping perennial grass producing coarse, erect stems reaching a meter in maximum height. The clumpy form of the grass helps it stabilize loose and blowing sand when it grows in desert dune habitat. The stems have nodes which are lined with long, sometimes curly hairs. The flower cluster is a series of hairy or brushlike rectangular spikelets. The grass produces relatively little viable seed and spreads mostly via its tillers and sometimes via rhizome. This grass acts as a nurse plant to seedlings of other species, such as cholla and barrel cactus, in turn receiving protection from herbivory by growing next to the spiny plants.
James’ Galletta Grass
Galleta or Hilaria (Pleuraphis) jamesii is the most common and widespread of the Hilaria species in the United States, where it ranges from southern Wyoming and northern Nevada to southern California, northern Mexico, and southwestern Kansas. It is especially abundant in desert grasslands and rocky canyons of southern Utah, Arizona, and New Mexico. As a warm season or “C4” perennial grass, galleta is more water-efficient than many grasses, and so can photosynthesize at high temperatures and under relatively droughty conditions. The species also flowers and produces seed in mid-summer rather than spring, and so is often less impacted by winter and spring grazing than “cool season” grasses. It grows in bunches of thin and tall stems up to 25 inches tall, with long, flat bladed leaves at its base. It produces relatively few seeds and spreads mainly by underground rhizomes.
Tobosa greens up readily after rain and turns ashy gray during drought. Hilaria mutica is perennial grass that is rhizomatous and forms sod. It usually grows 1–2 feet tall, sometimes reaching up to 3 feet. The stems have decumbent bases and erect tops. Most of the stiff, hairless leaves are basal. They are up to 6 inches long. The bases of the stems come from a thick, woody rootstock and a system of roots that penetrates up to 6 feet deep in the soil. It is native to Northern Mexico, and the Southwestern United States, in Arizona, New Mexico, Oklahoma, and Texas.
Red Grama Grass
This grass is tufted with erect (when young) or prostrate (at maturity) stems growing from short rootstocks. Older plants tend to be somewhat rhizomatous. The mostly basal leaves are short and narrow, about only 1/2” wide but up to 4” in length. The sheaths are shorter than the dark and naked internodes. Upper stem leaves are greatly reduced. The stems have two to seven persistent, pectinate spikes that are red or purplish in color. Each spike carries about 12 to 24 spikelets. The spikelets have three short, rough awns. Red Grama is a perennial, warm-season, native reaching 4.5 to 16 inches. It flowers in response to moisture and temperature and produces seeds from April to November.
Slim Tridens Grass
Slim tridens is a native, warm-season, perennial bunch grass. The height ranges from 8 to 12 inches. The leaf blade is narrow, and rolled giving a needlelike appearance and sometimes sparsely covered with fine hairs. The leaf sheath is shorter than the internodes and usually covered with short hairs. The ligule is a ring of hairs. The stems are erect, slender, and somewhat swollen at the base. The seedheads are dense panicles, spikelets with 6- to 8-flowered, and pale purplish. The back of the palea is densely covered with hair. It is native to Mexico and the southwestern quadrant of the United States, where it grows several types of habitat, including plateau and desert, woodlands, sagebrush, plains, and other areas with dry sandy and clay soils.
Indian Rice Grass
Synonyms: Achnatherum hymenoides, Oryzopsis cuspidata, Oryzopsis hymenoides, Stipa hymenoides
Oryzopsis hymenoides was first described and the name validly published by Johann Jakob Roemer and Josef August Schultes. It was later revised and reclassified by Percy Leroy Ricker but this revision did not meet the standards for valid publication. The currently accepted description was published by Charles Vancouver Piper in 1906. It likes to live in sandy soils and is adapted to dry places, but also lives in moist areas within drier environments; look for it where you see sagebrush, juniper, or ponderosa pine. Distinguishing Indian ricegrass from other grasses may sound difficult to someone who has not seen it before, but armed with a good picture and an idea of what to look for, it can be done. Look for a bunchgrass from 1 to 2½ feet tall. The leaves are tightly rolled from the edges, giving each leaf the look of a long, straight, skinny tube. The inflorescence is the easiest feature to distinguish. It is an open, branching panicle, consisting of long, undulating stalks that look like hairs. Each branch terminates in a single seed (or, technically, a single fruit, containing a single seed). The seed itself is covered with short hairs, is black, and is the portion used for food.
Panicum capillare is an annual bunchgrass growing decumbent or erect to heights exceeding 3 feet (1 m). It is green to blue- or purple-tinged in color. In texture it is quite hairy, especially on the leaves and at the nodes. The ligule is a fringe of long hairs. The inflorescence is a large open panicle which may be over half the total length of the plant, up to half a meter long. At maturity it fans out, spreading to a width over 20 centimeters. As the plant dies and dries, the panicle may break off whole and becomes a tumbleweed. It is a native plant to most of North America from the East Coast through all of the West Coast and California.
Thurber’s needlegrass is a densely tufted bunchgrass with erect culms (stems), 12 – 24 inches tall. The crown typically acquires a circular appearance, as the plant dies from the center outwards. The fibrous roots reach up to 2 feet deep. It begins growth in early spring, fruits from May to June, and seed ripens in late July. It continues growth until October. It often goes dormant through the summer and may green-up in the fall is soil moisture is adequate. It reproduces from seeds and tillers. Panicle is 3 to 9 inches long with single-flowered spikelets with sharp points and awned lemmas. The seed is about ¼ inch long. The awn is twice bent, over 5 inches long, and has short hairs on all but the tip. The glumes are greenish or purple-tinged. Leaf blades are rather narrow (<¼” wide), and 6 –10 inches long. The edges of the leaves are rolled upward and in.
Needle and Thread Grass
Hesperostipa comata is a perennial bunchgrass producing erect, unbranched stems to about 1 m (3 ft 3 in) in maximum height. The narrow inflorescence is up to 28 cm (11 in) long in taller plants, with the mature spikelet bearing a spiraling, hairy, spear-shaped awn up to 19 cm (7+1⁄2 in) in length. The seeds of this grass have hygroscopic extensions that bend with changes in humidity, enabling them to disperse over the ground. Each seed has an awn that twists several turns when the seed is released. Increased moisture causes it to untwist, and, upon drying, to twist again, thus the seed is drilled into the ground.
Bluebunch wheatgrass can grow up to three feet tall. It can often be distinguished from other bunchgrasses by the awns on its seedheads which stand out at an angle nearly 90 degrees from the stem. It is often bluish. The roots of the grass have a waxy layer that helps it resist desiccation in dry soils. In areas with more moisture the grass may produce rhizomes. The grass can be found in the United States, Canada, and Mexico from Alaska and Yukon south as far as Sonora and Nuevo León.
Idaho Fescue or Blue Bunchgrass
This fescue is a densely clumping long-lived perennial bunch grass with stems from about 30 to 80 centimeters in height. The stiff, short, rolling leaves are mostly located near the base of the tuft. The inflorescence has hairy spikelets which produce large awned fruits. The root system is thick and penetrates deeply into the soil. The roots have symbiotic mycorrhizae. There are no rhizomes; the plant reproduces from seeds and from budding with tillers. It is native to western North America, where it is widespread and common. It can be found in many ecosystems, from shady forests to open plains grasslands.
Southwestern Bushy Bluegrass
Andropogon eremicus grows in moist soils of seepage slopes and the edges of springs, from California to New Mexico and southward into Mexico. It is not common, but I have seen it at Ash Meadows and at the Calico Basin at Red Rocks. Not much written about it, Jim Boone (hike and bird) has photos from the Calico Basin. It reportedly grows to five feet although I have only seen it lower to 3-3.5 feet but Steve Matson shows photos on Calscape of 4 feet or so. Like most desert grasses it is a bunchgrass. The bushy red seedheads are the diagnostic feature.
(Andropogon eremicus) replaced (Andropogon glomeratus var. scabriglumis) in 2018
It is a perennial bunchgrass forming a clump of stems reaching up to 2 m (6.6 ft) tall. The stem bases are thick and tough, almost woody in texture. The fibrous green or gray-green leaves are up to 60 cm (24 in) in length. The inflorescence is long and generally wide open and spreading, bearing yellow spikelets with purplish bases. The grass produces abundant seeds, which are often dispersed in flowing water and germinate when embedded in sediment. Alkali Sacaton is native western North America and is usually found at elevations between 4200 and 6200 feet in the lowlands, floodplains, and in the drier areas such as desert valleys. Does best in areas with 12 to 18 inches of annual precipitation or equivalent in run-in water. It is common in the stream channels with alkaline soils. It withstands flooding and considerable soil deposition, and may occur in nearly pure stands.
Deergrass is characterized by dense, tufted basal foliage consisting of narrow pointed leaves that reach lengths of about 3 feet (0.91 m). The foliage ranges in color from light silver-green to purple. The spikelike stems are less than half an inch wide and 3–4 feet (0.91–1.22 m) in length. During bloom, the numerous flowered panicles often reach heights of five feet. The spikelets consist of a single awnless floret with a 3-nerved lemma. It is found in sandy or well-drained soils below 7,000 feet (2,100 m) in elevation in the Southwestern United States and parts of Mexico.
Great Basin Wild Rye
It is a perennial bunchgrass forming large, tough clumps up to about 2 metres (6.6 ft) tall and sometimes exceeding 1 metre (3.3 ft) in diameter. It has a large, fibrous root system and sometimes small rhizomes. The inflorescence is an unbranched, cylindrical spike divided into up to 35 nodes with several flower spikelets per node. It is a common native grass of western North America, including western Canada and the United States from California to Minnesota. It grows in many types of habitat, including grassland and prairie, forests, scrub, chaparral, and sagebrush. This mammoth statue bunchgrass with short rhizomes is the only grass that plays a significant role in the salt deserts on lake plains and the uplands through much of the pinyon-juniper zone.
Agropyron cristatum is one of several closely related grass species referred to as crested wheatgrass. It is unable to hybridize with its similar relatives, as it is a diploid species, whereas its closest relative, Agropyron desertorum, is a tetraploid species. It was introduced from Russia and Siberia to North America in the first half of the twentieth century, and widely used to reseed abandoned marginal cropland undergoing varying degrees of soil erosion and secondary succession.
Bromus tectorum, known as downy brome, drooping brome or cheatgrass, is a winter annual grass native to Europe, southwestern Asia, and northern Africa, but has become invasive in many other areas. It now is present in most of Europe, southern Russia, Japan, South Africa, Australia, New Zealand, Iceland, Greenland, North America and western Central Asia. In the eastern US B. tectorum is common along roadsides and as a crop weed, but usually does not dominate an ecosystem. It has become a dominant species in the Intermountain West and parts of Canada, and displays especially invasive behavior in the sagebrush steppe ecosystems where it has been listed as noxious weed. The reduction of native plants and the increased fire frequency caused by B. tectorum prompted the United States Fish and Wildlife Service (USFWS) to examine if the greater sage-grouse needed to be listed as a threatened or endangered species due to habitat destruction.
African foxtail grass is a perennial grass growing to 20 to 120 cm (10 to 50 in) tall. The leaves are linear, 1–10 inches long and about 1/4” wide. The flowers are produced in a panicle up to 5.5 inches long and up to to 1 inch wide. African foxtail grass is native to tropical Africa, the Mediterranean region and the hotter and drier parts of Asia. It is a deep-rooted grass, tolerates drought, and will grow at altitudes of up to 2,000 m (6,600 ft). It is considered a good forage grass in Africa. It was introduced in the 1930s into Arizona, United States, to provide grazing. The introduction was largely unsuccessful but the grass began to appear as a weed beside highways and in cleared fields or over-grazed land. It spreads very quickly and will often kill local native plants, such as palo verdes, by taking away nearby water. This plant has a very low ignition threshold and can burn even during the peak growing season. Its flammability (injurious to neighbors) and quick regrowth allow it to compete successfully against almost all vegetation in the Sonoran Desert region.
Non-native Grass Fire Risks
The woody sagebrush species of Nevada do not sprout after the tops are burned in wildfires. This has major significance as the frequency of wildfires has greatly increased. Following wildfires, gray and green rabbitbrush, horsebrush, and ephedra species became the transitory woody dominants until sagebrush plant Is gradually reestablished as seedlings. Sagebrush communities continue as understory species in the pinyon-juniper woodlands as you rise in elevation on Nevada mountain ranges.
I plan to add more species, but I thought I would start with these. As always, I hope you enjoyed.