Agoseris grandiflora is a species of flowering plant in the daisy family known by the common names bigflower agoseris and grassland agoseris. It is native to western North America from British Columbia to California to Utah, where it grows in many habitat types. This is a perennial herb producing a basal patch of leaves of various shapes reaching maximum lengths of 50 centimeters. There is usually no stem, but there is sometimes a rudimentary one. The upright part of the plant is actually the peduncle of the flower cluster, which can approach a meter in height. It is coated in soft white hairs. The flower head at the top is up to 4 centimeters wide and lined with reddish or purplish green phyllaries with curling tips.

Agoseris retrorsa is a species of flowering plant in the daisy family known by the common name spearleaf agoseris. It is native to western North America from Washington to Utah to Baja California, where it grows in many types of habitat, including chaparral, scrub, and coniferous forest. It is a perennial herb forming a base of leaves about a number of erect, thick, wool-coated flower clusters up to half a meter in height. The narrow leaves are linear to lance-shaped, and spearlike with curving toothlike lobes along the edges. The flower cluster bears a single flower head which is several centimeters wide when fully open. It is lined with woolly, pointed phyllaries which are green, often with reddish purple longitudinal streaks or stripes. The flower head contains many golden yellow ray florets, the outer ones usually darker in color. The fruit is an achene with a plumelike pappus of white bristles.

Agrostis blasdalei is a species of grass known by the common name Blasdale's bent grass. It is endemic to the coast of northern California, where it grows in habitat along the immediate coastline, such as dunes and bluffs. It is a perennial grass growing in tufts up to 30 centimeters tall. It has short, thready leaves a few centimeters long. The flower cluster is a thin cylindrical array of tiny spikelets, each up to 4 millimeters in length.

Agrostis exarata is a species of grass known by the common names Pacific bentgrass, spike bentgrass, and spike redtop. It is native to western North America from Texas to the Aleutian Islands. This is a common perennial grass reaching one to three feet in height with long, thin, flat leaves each with a ligule of 2 to 4 millimeters. The tuft flower cluster may be up to 30 centimeters long and is usually dense with tiny spikelets. It reproduces mainly by seed, but it can also spread via rhizome. This bunchgrass occurs in many plant communities in varied climates. It is considered good forage for livestock.

Agrostis hallii is a species of grass known by the common name Hall's bentgrass. It is native to the west coast of the United States from far southern Washington to central California, where it grows in the woodlands and forests of the coastal mountain ranges. This is a rhizomatous perennial grass growing up to about a meter tall. It has flat leaves up to 20 centimeters long and thin or dense flower clusters of spikelets.

Agrostis idahoensis is a species of grass known by the common name Idaho bent grass. It is native to western North America from Alaska to California to Colorado, where it grows in several habitat types. It is a perennial grass growing in short tufts up to 30 centimeters tall. The leaves are thready and a few centimeters long. The flower cluster is an open, thin array of wispy branches bearing spikelets each a few millimeters long.

Thingrass (Agrostis pallens) is a perennial grass that makes an eco-friendly lawn alternative, requiring half the water of non-native grasses. Its deep green color lasts year-round with weekly summer watering, and it tolerates light foot traffic.

Thingrass grows up to 2 feet tall but typically reaches about 1 foot in height and width. Its narrow leaves, usually under 2 inches long, complement its feathery flower clusters. Mowing is optional; without it, the grass has a meadow-like appearance.

Adaptable to various soils, it thrives in sun or part shade, making it an ideal ground cover for under trees. Thingrass also attracts butterflies and moths, adding both beauty and ecological value.

Tolerates almost any soil type. Prefers sun in coastal sites, and sun or part shade in inland sites. Selected for the garden.

Agrostis scabra is a common species of grass known by the common names rough bent grass and ticklegrass. A tumbleweed, it is native to much of North America, and widely known elsewhere as an introduced species. It occurs in most of the United States except parts of the Southeast and most of Canada except for the farthest northern regions. It can be found in Mexico, and across Alaska to far eastern Asia as far south as Korea. It is resident in a great variety of habitats, from warm coastal valleys to the alpine climate of high mountain ranges. This is a perennial grass growing mainly upright in form to heights around 75 centimeters. The leaves are rough with tiny hairs and up to about 14 centimeters long. The flower cluster is a wide open array of spreading, thready branches bearing spikelets each a few millimeters long. The tolerance of this grass to alpine climates makes it a good plant to use in revegetating disturbed land in such regions. It is known to spring up on sites where few other plants can grow, such as abandoned coal mines and soils polluted with sulfur, copper, and nickel.

Alisma triviale (Northern water plantain, Northern water-plantain) is a perennial semi-aquatic or aquatic plant in the Water-plantain family (Alismataceae). It grows in shallow water or mud. Northern water plantain is native to Canada, the United States, and Northern Mexico.

Allenrolfea is a monotypic plant genus containing the single species Allenrolfea occidentalis, the iodinebush. This is a low-lying shrub of the southwestern United States and northern Mexico, where it grows in sandy, often salty, distinctly alkaline soils, such as desert washes and saline dry lakebeds. It is a common member of the alkali flat ecosystem. The knobby green stems are fleshy and appear jointed at the internodes between segments. Often the segments are so short they are nearly round. The leaves appear as flaky scales scattered across the surface of the stems. The genus was named for the English botanist Robert Allen Rolfe. The seeds of iodinebush have been used as food in North America in prehistory.

Allium abramsii is a species of wild onion known by the common name Abrams' onion. It is endemic to the central Sierra Nevada in California, where it grows in the coniferous forest understory in granite sand soils. This onion grows from one or more bulbs each just over a centimeter wide attached to a thick rhizome. It reaches a maximum height of about 15 centimeters with usually one curving cylindrical leaf. The flower cluster contains up to 40 pink or purplish flowers with lance-shaped petals.

Allium amplectens is a species of wild onion known by the common name narrowleaf onion. It is native to western North America where it grows in woods and especially in clay and serpentine soils. It grows from a pinkish-brown bulb and sends up a naked green stem topped with an flower cluster. When closed the flower cluster is wrapped in bright pink to magenta leafs. It opens to produce between 10 and 50 shiny white to pale pink flowers, each under a centimeter wide. The six stout stamens and the ovary are white or tinted pink or lavender. It is a fairly widespread species.

Tolerates almost any soil type. Selected for the garden.

Allium anceps, known by the common names twinleaf onion and Kellogg's onion, is an onion that is native to the Great Basin of North America. It is widespread in Nevada and adjacent portions of California, Idaho and Oregon. It grows in relatively small and isolated areas, but growth is typically dense, often to the exclusion of all other vegetation. It has two flat and narrow leaves which first appear in late winter, and grow up to 10 centimeter in length. It has a pink or purple flower head which grows on a separate stalk starting in mid-spring. By early summer the above-ground portions of the plant die, and there is little evidence of the plant's existence throughout much of the year. The bulb is white with a yellow or brown husk, and approximately 1 centimeter in diameter. It is edible, although it has a strong oniony taste.

Allium burlewii is a species of wild onion known by the common name Burlew's onion. It is endemic to California, where grows in the granitic soils of several of the central and southern mountain ranges. This is a short-stemmed onion, growing to heights of just a few centimeters from an oval-shaped bulb. It sprouts a single long, pointed onion leaf. The flower cluster contains up to 20 dark-veined purple flowers each up to a centimeter long with dark purple anthers.

Allium campanulatum is a species of wild onion known by the common name dusky onion. This is a flowering plant native to the western United States from Washington to California as well as Nevada. The dusky onion grows from a gray-brown bulb one to two centimeters wide which may extend tiny rhizomes and produce small daughter bulblets. It rises on a stout stem and has usually two long, drooping onion leaves. Atop the stem is an flower cluster of 10 to 50 flowers. Each flower is half a centimeter to one centimeter wide and is pink, purple, or less often white, and each tepal has a dark-colored base. The petals are variable in shape, from narrow and very pointy to spade-shaped. The dusky onion grows in low mountains, especially in dry areas.

Allium cratericola is a species of wild onion known by the common name Cascade onion. It is endemic to California, where is an uncommon member of the flora in several of the state's mountain ranges. This onion grows a short stem up to 10 centimeters tall from a brown-coated oval-shaped bulb. There are one or two long, pointed leaves up to four times the length of the stem. The flower cluster contains up to 20 rosy pink flowers clustered densely together.

Allium crispum is a species of wild onion known by the common name crinkled onion. It is endemic to California, USA, where it grows along the Central Coast, often in clays and serpentine soils. This onion grows from a bulb one to one and a half centimeters wide and sends up naked green stems topped with flower clusters of many flowers, each on a short pedicel. The flowers are magenta in color and have six triangular petals. The inner three petals are smaller and crinkled like cloth and may curl under.

Allium denticulatum is a species of wild onion known by the common name toothed wild onion. It is endemic to California, where it grows in the western Mojave Desert and adjacent Tehachapi Mountains and the southern Sierra Nevada. This onion grows from a reddish brown spherical to oval-shaped bulb just over a centimeter long. It produces a stem up to 18 centimeters tall and a single cylindrical leaf up to twice as long as the stem. The flower cluster contains up to 30 flowers with deep pink to purplish petals which are toothed at their tips.

Allium diabolense is a species of wild onion known by the common name serpentine onion. It is endemic to central California, where it is known from the southern Coast Ranges and the Transverse Ranges. This onion grows from a reddish brown bulb just over a centimeter long. It produces a stem up to 20 centimeters tall and one leaf which is longer than the stem. The flower cluster contains up to 50 dark veined pink-tinted white flowers.

Allium dichlamydeum is a species of wild onion known by the common name coastal onion. It is endemic to California where it grows on sea cliffs on the coastline in the northern half of the state. The coastal onion grows from a brown or gray bulb one to one and a half centimeters wide. It has a stout naked green stem surrounded by 3 to 6 long onion leaves. Atop the thick stem is an flower cluster of five to 30 flowers. Each flower has six oval-shaped dull-pointed petals in shades of bright magenta to fuchsia and each flower is about a centimeter wide.

Allium falcifolium is a species of wild onion known by the common name scytheleaf onion. It is native to northern California and southern Oregon, where it grows in heavy, rocky soils, especially serpentine soils. The scytheleaf onion grows from a reddish-brown bulb one to two centimeters wide. The reddish or yellowish green stem is flattened such that it is thick in the center and thin along the edges. There are usually two leaves, which, as its common name suggests, are curved like the blade of a scythe The stem is short and topped with an flower cluster of 10 to 30 flowers, each of which is one to one and a half centimeters wide. Each flower has six pinkish, red-purple, or white-streaked purple petals.

Allium fimbriatum is a species of wild onion known by the common name fringed onion. It is native to California and Baja California. The fringed onion grows from a reddish-brown bulb one to two centimeters wide and sends up a naked brown or green stem. Atop the stem is an flower cluster of up to 75 flowers, each just under a centimeter wide on average. The flowers are variable in color, from pink to purple and often with white areas. The petals are also variable in shape, from narrow and pointy to spade-shaped. There are several distinct varieties of the species as well.

Fringed Onion (Allium fimbriatum var. fimbriatum) is a native perennial herb that grows in northern, southern and central California. It tends to grow in dry slopes and flats, at elevations from 1000-8900 feet.

Purdy's Onion (Allium fimbriatum var. purdyi) is a rare native perennial herb that grows in Central and Northern California, primarily in the North Coast and North Coast Range regions. It tends to grow in dry slopes and flats, at elevations from 1000-8900 feet.

Allium haematochiton is a North American species of wild onion known by the common name redskin onion. It is native to northern Baja California, Sonora, and southern California as far north as Kern County. It grows on the slopes of the hills and mountains, such as those of the Peninsular Ranges, Transverse Ranges, and southern California Coast Ranges. . Allium haematochiton has a small rhizome associated with clusters of brightly colored red bulbs. From these grow several naked green stems, each with a few withering, curling leaves. Atop each stem is an inflorescence of several flowers, each on a short pedicel. Each flower is just under a centimeter wide and white to pinkish with dark midveins. There are six stout stamens around a white or pink ovary. USDA Plants Profile 

Allium howellii is a species of wild onion known by the common name Howell's onion. It is endemic to California, where it grows in the granite and serpentine soils of several of the local mountain ranges, hills, and valleys. This is a tall onion plant, producing a stem which may exceed half a meter in height from a reddish-brown bulb one to two centimeters long. There is a single cylindrical leaf about as long as the stem. The flower cluster holds up to 100 dark-veined lavender to white flowers, each under a centimeter long.

Mt. Pinos Onion (Allium howellii var. clokeyi) is a rare native perennial herb that grows in Southern and Central California, primarily in the Transverse Range region. It tends to grow in granitic soils, at elevations from 700-6100 feet.

Howell's Onion (Allium howellii var. howellii) is a common native perennial herb that grows in central California. It tends to grow in granitic soils, at elevations from 700-6100 feet.

Allium hyalinum is a species of wild onion known by the common name glassy onion. It is endemic to California, where it is a common species of the San Joaquin Valley and the Sierra Nevada foothills. The glassy onion grows from a cluster of bulbs, with each bulb sending up a tall stem. Atop each stem is an flower cluster of up to 25, but usually fewer, white or pink-tinted white flowers. The flowers have six shiny petals which become transparent as they age.

Allium jepsonii is a species of wild onion known by the common name Jepson's onion. It is endemic to the Sierra Nevada foothills of central California. This onion grows to a height between about 20 and 40 centimeters from one or two oval-shaped bulbs. There is a single cylindrical leaf which is about the same length as the stem. The flower cluster holds 20 to 60 small flowers, each under a centimeter long with pink-veined white petals with curling tips.

Allium lacunosum is a species of wild onion known by the common name pitted onion. It is endemic to California, where it is a common member of the flora in many types of habitat, from bayside to mountain to desert. This onion grows from a thick-coated yellowish-brown bulb one or two centimeters long. The stem reaches up to about 35 centimeters in maximum height and there are usually two leaves which may be as long or longer than the stem. The flower cluster contains up to 45 dark-veined white to pale pink flowers, each less than a centimeter long. There are four varieties of this species, three of which are somewhat uncommon.

Pitted Onion (Allium lacunosum var. lacunosum) is a common native perennial herb that grows in southern and central California. It tends to grow in drive open slopes, at elevations from 200-6900 feet.

Allium haematochiton is a North American species of wild onion known by the common name redskin onion. It is native to northern Baja California, Sonora, and southern California as far north as Kern County. It grows on the slopes of the hills and mountains, such as those of the Peninsular Ranges, Transverse Ranges, and southern California Coast Ranges. Allium haematochiton has a small rhizome associated with clusters of brightly colored red bulbs. From these grow several naked green stems, each with a few withering, curling leaves. Allium haematochiton has a small rhizome associated with clusters of brightly colored red bulbs. From these grow several naked green stems, each with a few withering, curling leaves. Atop each stem is an inflorescence of several flowers, each on a short pedicel. Each flower is just under a centimeter wide and white to pinkish with dark midveins. There are six stout stamens around a white or pink ovary. USDA Plants Profile

Allium obtusum is a species of wild onion known by the common name red Sierra onion. It is native to the granite hills and mountains of Nevada and eastern California where it is a common member of the local flora. The red Sierra onion grows from a bulb one or two centimeters wide and bears a stem which may be tall or short. Atop the stem is an flower cluster of up to 60 flowers which May 4 to 12 millimeters wide. The flowers are white to pink with dark midveins.

Red Sierra Onion (Allium obtusum var. conspicuum) is a common native perennial herb that grows in Central and Northern California, primarily in the Sierra Nevada Foothills and High Sierra Nevada regions. It tends to grow in granitic sands, at elevations from 2600-11500 feet.

Red Sierra Onion (Allium obtusum var. obtusum) is a common native perennial herb that grows in Central and Northern California, primarily in the High Cascade Range, the Sierra Nevada Foothills and High Sierra Nevada regions. It tends to grow in granitic sands, at elevations from 2600-11500 feet.

Allium peninsulare is a North American species of wild onion. It is known by such common names as Mexicali onion and Peninsula onion; the former referring to the Mexican city just south of the US/Mexican border, the latter referring to the Peninsula of Baja California. It is widespread in California, USA, where it grows in the California Coast Ranges, Sierra Nevada foothills, some of the Channel Islands, and Peninsular Ranges. The range extends south into the northernmost part of Baja California and north into southern Oregon. Allium peninsulare is usually found in Valley Grassland, Foothill Woodland, and Coastal Chaparral at elevations up to 1100 m (3660 feet). The plant produces a bulb 8-15 mm wide and has two to three channeled to more or less cylindrical leaves. Between May and July, it sends up a 12-45 cm scape topped with an umbel of 5-35 flowers, each on an 0. 8-4 cm pedicel. The flowers are red-purple and have six triangular tepals. The three inner tepals are smaller than the outer ones and have teeth along the margins. Allium peninsulare is usually found in Valley Grassland, Foothill Woodland, and Coastal Chaparral at elevations up to 1100 m (3660 feet). The plant produces a bulb 8-15 mm wide and has two to three channeled to more or less cylindrical leaves. Between May and July, it sends up a 12-45 cm scape topped with an umbel of 5-35 flowers, each on an 0. 8-4 cm pedicel. The flowers are red-purple and have six triangular tepals. The three inner tepals are smaller than the outer ones and have teeth along the margins. Varieties: Allium peninsulare var. franciscanum --- leaves arched; stigma, unlobed or obscurely 3- lobed --- central California from Mendocino County to Monterey County, Allium peninsulare var. peninsulare - leaves straight, stigma strongly 3 - lobed --- widespread from Baja California to Oregon

Allium platycaule is a species of wild onion known by the common name broadstemmed onion or flat-stem onion. It is native to northeastern California and nearby parts of Oregon and Nevada where it is found on slopes of some elevation. This onion grows from a gray bulb two to three centimeters wide and has a flattened stem which may bulge in the middle and narrow to thin wings along the sides. The long, flat leaves are sickle-shaped. Atop the stem is an flower cluster which may have as many as 90 flowers in it. Each flower may be up to a centimeter and a half wide but the petals are quite narrow so as to be almost threadlike. The flower cluster therefore may be a dense ball of filaments. The flowers are generally bright pink to magenta. The leaves, bulbs, and seeds were utilized as food by the Paiute people.

Congdon's Onion (Allium sanbornii var. congdonii) is a rare native perennial herb that grows in Central and Northern California, primarily in the Sierra Nevada Foothills region. It tends to grow in rocky outcrops, at elevations from 1000-4600 feet.

Allium serra is a species of wild onion known by several common names, including jeweled onion, pom-pon onion, and serrated onion. It is endemic to northern California. It favors hard soils with rock and clay, including serpentine soil. The plant comes from a small herringbone-patterned bulb an average of one centimeter in diameter. It has a long stem on which it bears a tightly bunched flower cluster of flowers. The attractive bright pink flowers are thimble or bell-shaped, often iridescent when new and becoming papery as they dry.

Allium tolmiei is a species of wild onion native to the northwestern United States, and found in Lassen, Trinity and Modoc counties in California. It has white or pink flowers, and thick curving green leaves. Allium is the onion genus, with 600-750 species, making it one of the largest plant genera in the world. Tolmie's Onion is one of them. William Fraser Tolmie (aka "Dr. Tolmie") (February 3, 1812 - December 8, 1886) was a Canadian surgeon, fur trader, scientist, and politician. He was born in Inverness, Scotland in 1812 and by 1833 moved to the Pacific Northwest in the service of the Hudson's Bay Company (HBC). Plants bearing his name include Tolmie's star-tulip (Calochortus tolmiei) and Tolmie's onion (Allium tolmiei).

Tolm's Onion (Allium tolmiei var. tolmiei) is a uncommon native perennial herb that grows in Northern California, primarily in the Warner Mountains and Modoc Plateau regions. It tends to grow in rocky clay flats, at elevations from 4900-7200 feet.

Allium tuolumnense is a rare species of wild onion known by the common name Rawhide Hill onion. It is endemic to Tuolumne County, California, where it is known only from a small section of the Sierra Nevada foothills. It is a plant of serpentine soils. This onion grows from a reddish-brown bulb one to two centimeters long, producing a slender erect stem up to 50 centimeters tall and usually a single leaf approximately the same length. The stem is topped with a hemispheric flower cluster holding 20 to 60 flowers, each on a pedicel one or two centimeters long. Each flower is just under a centimeter wide when fully open, with six white or pink oval-shaped petals. There are six stamens and the ovary has six pointed crests.

Allium validum, known by several common names including swamp onion, wild onion, and Pacific onion, has been previously classified as a member of the lily family, Liliaceae; however, it is now thought of to be in the Alliaceae. Allium validum is native to California. The Allium validum bulb is three to five centimeters long, ovoid and clustered on the short end. The outer coat of the stout rhizome is brown or gray in color, fibrous, and vertically lined. The stem is 50 to 100 centimeters long and angled. There are three to six leaves more or less equal to the stem and the leaves are flat or more or less keeled. There are 15 to 40 flowers with pedicels being seven to twelve millimeters in length. The flower itself is six to ten millimeters, its perianth parts are more or less erect, narrowly lance-shaped, acuminate, and entire with a rose to white color. The stamens are exerted and there is no ovary crest.

Allium yosemitense is a species of wild onion known by the common name Yosemite onion. It is endemic to the central Sierra Nevada of California, where it is known from only a few areas in the vicinity of Yosemite. This onion grows from a bulb two to three centimeters long, producing a stem up to about 23 centimeters in maximum height and two long, flat leaves which are usually a bit longer. The flower cluster bears up to 50 white or pink flowers, each on a pedicel which may be over 3 centimeters long.

Alnus incana (Grey or Speckled Alder) is a species in the Betulaceae (Birch) family with a wide range across the cooler parts of the Northern Hemisphere. In California it is found primarily in the Sierras. It is a small to medium size tree 15-20 meter tall with smooth grey bark even in old age, its life span being a maximum of 60-100 years. The leaves are matte green, ovoid, 5-11 centimeter long and 4-8 centimeter broad. The flowers are catkins, appearing early in spring before the leaves emerge, the male catkins pendulous and 5-10 centimeter long, the female catkins 1.5 centimeter long and one centimeter broad when mature in late autumn. The seeds are small, 1-2 millimeter long, and light brown with a narrow encircling wing. The Grey Alder has a shallow root system, and is marked not only by vigorous production of stump suckers, but also by root suckers, especially in the northern parts of its range. The wood resembles that of the black alder, but is somewhat paler and of little commercial value.

Mountain Alder (Alnus incana ssp. tenuifolia) is a native tree or shrub that grows in northern, southern and central California. It is fast growing and moderately long-lived. It grows in an upright form to a height of 20 feet, with active growth during the spring and summer. Flowers are purple and bloom in the early spring. Leaves are dark green and deciduous. It tends to grow in wet places, at elevations from 4500-8000 feet.

White alder (Alnus rhombifolia) is a fast-growing deciduous tree in the birch family (Betulaceae), native to western North America at elevations of 300–7,900 feet. It thrives in moist soils, often found along streambanks and other wet areas.

This tree provides excellent shade, with dark green leaves in summer that drop in winter. In early spring, before the leaves emerge, white alder produces noticeable male catkins, which hang in clusters and release large amounts of pollen. The female catkins mature in autumn, resembling small cones that may persist on the tree for up to a year.

White alder is heat and wind tolerant but requires deep watering to establish. Its roots can be invasive, so it should be planted with caution, especially near structures or small residential gardens. However, it is an excellent choice for woodland plantings and riparian areas.

This tree has high wildlife value. It serves as a larval food plant for the Western Tiger Swallowtail butterfly and provides habitat and food for various bird species.

Alopecurus geniculatus is a species of grass known by the common name water foxtail or Marsh foxtail. It is native to much of Eurasia and North America, where it grows in moist areas. This is a perennial grass forming bunches of erect stems up to about 60 centimeters in maximum height. The leaves are 8 to 12 centimeters in maximum length. The flower cluster is a dense panicle up to 6 or 7 centimeters long which blooms in dusty yellow-orange anthers.

Aloysia wrightii is a species of flowering plant in the verbena family known by the common names Wright's beebrush and oreganillo. It is native to the southwestern United States and northern Mexico, where it can be found in desert, scrub, and woodland habitat. This is a thickly branching shrub which reaches nearly two meters in maximum height and is generally rounded in form. It has small, oval-shaped to nearly round leaves each no more than two centimeters long. The leaves have lightly toothed edges and hairy undersides. The flower cluster is a narrow, woolly spike up to 6 centimeters long, with small, widely spaced white flowers.

Ambrosia acanthicarpa is a species of ragweed known by the common names flatspine burr ragweed, annual burrweed, and annual bur-sage. This spiny, weedy plant grows in clumps of many erect stems which may reach over a meter in height. Its gray-green stems are covered in a coat of stiff, bristly hairs. The few rough leaves are several centimeters long. The racemes of flowers are more plentiful, with each hairy flower head a few millimeters wide. The spiny, burr-like pistillate heads have pointed, twisting leafs and the staminate heads are rounded. This ragweed is native to western North America. It is adaptable and grows well in disturbed areas, easily becoming weedy.

Ambrosia ambrosioides, also known as canyon ragweed or chicura is a ragweed found in the deserts of northern Mexico and ranging into the southern half of Arizona. Growing as a shrub from 1-2 meters high, its elongate, coarsely-toothed leaves range from 4-18 centimeter long and 1.5-4 centimeter wide. It is monoecious, with both terminal and axillary racemes consisting of staminate heads occurring above their pistillate counterparts. Flowering occurs mainly in February through April. The fruits are 10-15 millimeter burs covered with hooked spines.

Ambrosia chamissonis is a species of ragweed known by the common names Silver Burr Ragweed, Silver Beachweed and (Silver) Beach Bur(r). It is known from most of the coastline of western North America from Alaska to Baja California, where it is a resident of beaches and other sandy coastal habitat. This is a large, sprawling perennial herb exceeding three meters in maximum width. The stems are roughly or softly hairy and longitudinally ridged. The plentiful leaves are a few centimeters long, woolly and silver-green, and variable in shape. The plant is monoecious, with male and female flowers on each individual. Staminate (male) flower heads containing many pale colored florets occur at the tip of the flower cluster, with pistillate (female) flower heads clustered below them. Each pistillate head contains a single tiny flower which develops into a fruit. The fruit is a brown bur up to a centimeter wide covered in sharp spines.

Ambrosia chenopodiifolia is a species of ragweed known by the common name San Diego Burrsage or San Diego Burr Ragweed. It is native to Baja California, and California as far north as San Diego County, where it is a member of the coastal sage scrub plant community. This is a thickly branching shrub exceeding 3 meters in maximum height. The leaves are ovals up to 3 centimeters long and coated in white hairs. They are sometimes lobed. Like other ragweeds it is monoecious, with each flower cluster bearing heads of pistillate (female) flowers below a cluster of staminate (male) flowers. The flower cluster is spiny, especially when in fruit. The fruit is a spherical, woolly bur about half a centimeter long covered in hooked spines.

Ambrosia dumosa, the burro-weed or white bursage, is a common constituent of the creosote-bush scrub community throughout the Mojave desert of California, Nevada, and Utah and the Sonoran Desert of Arizona and northwestern Mexico. Ambrosia dumosa has been studied to determine allelopathic interactions with creosote bush, Larrea tridentata, which produces a chemical that inhibits the growth of A. dumosa. Other studies have suggested that A. dumosa roots produce a chemical that causes them to grow away from conspecific roots, preventing competition for water resources. In addition to burrow-weed, A. dumosa is also commonly called bur sage, burro weed, and burro bush.

Hymenoclea monogyra (also, Ambrosia monogyra) is a species of flowering plant in the daisy family known by the common name singlewhorl burrobrush. It is native to the southwestern United States and northern Mexico, where it grows in deserts and adjacent mountains and dry valleys. This is a thickly branching shrub reaching heights from one to four meters. The thin stems are covered in narrow, hairy leaves and flower in large flower clusters of staminate and pistillate flowers. The staminate flowers have translucent white corollas and the pistillate flowers are rounded, fruit-bearing structures. The fruit is an achene with a single whorl of several papery wings.

Ambrosia psilostachya is a species of ragweed known by the common names Cuman ragweed, perennial ragweed, and western ragweed. It is native to most of North America including all of southern Canada, nearly all of the continental United States, and the northern half of Mexico. It is a common plant in many habitat types, including disturbed areas such as roadsides. It can be found in parts of Eurasia as an introduced species. This is an erect perennial herb growing a slender, branching, straw-colored stem to a maximum height near two meters, but more often remaining under one meter tall. Leaves are up to 12 centimeters long and vary in shape from lance-shaped to nearly oval, and they are divided into many narrow, pointed lobes. The stem and leaves are hairy. The top of the stem is occupied by an flower cluster which is usually a spike. The species is monoecious, and the flower cluster is composed of staminate (male) flower heads with the pistillate heads located below and in the axils of leaves. The pistillate heads yield fruits which are achenes located within oval-shaped greenish-brown burs about half a centimeter long. The burs are hairy and sometimes spiny. The plant reproduces by seed and by sprouting up from a creeping rhizome-like root system. This plant had a number of medicinal uses among several different Native American groups.

Ambrosia pumila is a rare species in the Asteraceae (Sunflower) family known by the common names San Diego Ambrosia and San Diego Ragweed. It is native to a very limited area in far southern California and Baja California where it grows in a variety of habitats along the coastal strip, inland valleys and foothills at elevations below 2,000 ft. This is a perennial herb not exceeding half a meter in height. The leaves are gray-green, fuzzy, and divided into numerous minute lobes to give a feathery appearance. They are up to 13 centimeters long, not counting the winged petioles. The flower cluster is tipped with staminate (male) flower heads above several larger pistillate (female) heads. The pistillate heads each yield usually one fruit, which is a fuzzy burr only a few millimeters wide with short, soft spines. However, it rarely produces viable seed, usually spreading by its rhizome, forming clonal groupings. It is adapted to dry habitat, but only on upper floodplain fringes, or adjoining depressions containing vernal pools or similar structures. It is a plant of open habitat and is not tolerant of heavy shade. If not given supplemental summer water it will become deciduous but will come back from the rhizome after winter rain. This is not an easy plant to find and infrequently used in residential gardens. It is important for restoration projects in areas of appropriate habitat, and it may be useful in gardens seeking to specialize in rare plants of southern California.