Alturas Field Office

Invasive Species, Noxious Weeds 
Alturas Field Office Area 

Dalmatian toadflax
Stout perennial to 4 feet. Leaves blue-green and waxy-like, heart shaped, clasping stem, less than 2 inches long, alternately arranged and crowded on one stem. Flowers yellow, two lipped, with an orange, hairy center. Flower has a long spur, resembling a snapdragon flower. Reproduces by seed and creeping root system.
Linaria dalmatica

Diffuse knapweed
A slender, highly branched annual or short-lived perennial 1 to 2 feet. Stems rough to the touch. Leaves narrow, pinnately divided below, reduced above. Flowers numerous, narrow, with white to rose, but sometimes purplish, ray flowers. Phyllaries with marginal, comb-like bristles and a distinct slender spine on the tip. Seeds are brown or grayish, without bristles.
Centaurea diffusa 

Dyers woad
Winter annual, biennial, or short-lived perennial 1 to 4 feet. The large tap root may exceed 5 feet in depth, and can sprout new plant if the original plant is severed. Leaves bluish green, alternate and basal, with a whitish nerve on the upper surface of the blade. Flowers yellow, small, and crowded into flat-topped clusters. Purplish-brown seed pods contaiing a single seed appear near med-summer giving this weed a totally different appearance from the other mustards.
Isatis tinctoria

Hoary cress
Deep rooted perennial to 3 feet. Leaves blue-green, lance-shaped. Lower leaves stalked, while upper leaves with two lobes clasping the stem. Many clusters of white flowers give a white, flat-topped appearance. Flower with 4 petals. Seed capsules heart-shaped, containing 2 reddish-brown seeds separated by a narrow, papery partition. Reproduces from both root segments and seed.
Cardaria draba

St. Johnswort
Perennial 1 to 3 feet with erect, two-ridged stems and numerous rust-colored branches. Leaves opposite, oblong, entire, covered with tiny transparent dots. Flowers numerous, bright yellow, with five separate petals that twist after flowering. Peltals about 1/2 inch long with occasional minute black dots around the edges. Stamens numerous, arranged in three groups.
Hypericum perforatum

 Aggressive winter annual 1/2 to 2 feet. Leaf blades generally 1/8 inch wide or less, rolled. Inflorescence long-awned spike nearly as wide as long. Mature awns or beards twisted, 1 to 4 inches long, stiff, finely barbed. Sometimes confused with foxtail or squirreltail, however spike head does not break apart as seeds mature. Individual awn-florets fall away, leaving a bristly head of awn-like glumes that will persist over winter.
Taeniatherum caput-medusae

 Leafy spurge
A glabrous perennial, up to 3 feet. Leaves narrow, alternate, 1 to 4 inches long. Numerous clusters of small, yellow-green flowers subtended by paired, heart-shaped, yellow-green bracts. Entire plant contains a milky juice. Reproduces by seed and vigorous creeping root system.
Euphorbia esula

Perennial pepperweed
Perennial 1 to 6 feet. Leaves lanceolate, bright green to gray-green, smooth to toothed margin. Basal leaves larger than upper leaves. White flowers develop in dense clusters near the ends of branches. Fruit a two-seeded capsule. Reddish-brown seeds round, flat, slightly hairy, and about 1/16 inch long. 
Lepidium latifolium

PuncturevineTribulus terrestris L.Zygophyllaceae: Caltrop familyAnnual with prostrate or somewhat ascending, mat forming trailing stems, each about ½ to 5 feet long.  Leaves opposite, hairy, and divided into 4 to 8 pairs of leaflets.  Flowers yellow, with 5 petals.  Fruit hard, about ½ inch across, separating into five parts when mature, each with 2 to 4 sharp, hard spines resembling a goat’s head.  Flowers April to October.Native to Mediterranean.  Grows in pastures, cultivated fields, waste areas, and disturbed sites such as roadways.  Toxic to livestock in vegetative condition.  It particularly thrives in sandy and sandy loam soils.  The hard spiny burs damage wool, and may be injurious to livestock as well as humans’ bare feet, dogs’ pads, and bike tires.  Other common names include goathead, caltrop, and Mexican or Texas sandbur.Puncturevine is widespread throughout northeastern California and northwestern Nevada with scattered occurrence.
Tribulus terrestris

 Purple loosestrife
Rhizomatous perennial with erect stems, 2 to 6 feet. Leaves lance-shaped, simple, entire, and opposite or whorled. Flowers rose-purple, with 5 to 7 petals, less than 1/2 inch long, arranged spike-like and terminal on the stem.
Lythrum salicaria

 Russian knapweed
Perennial forming dense colonies by shoots from widely spreading black roots. Stems erect, openly branched, up to 3 feet. Lower leaves deeply, but not so finely, divided; upper leaves entire or serrate. Flowers 1/4 to 1/2 inch in diameter, numerous on the ends of branches. Ray flowers pink to lavender. Phyllaries pearly, rounded or pointed, with papery margins. Seeds small, from 1/8 to 1/4 inck long, with numerous whitish bristles.
Acroptilon repens

 Spotted knapweed
Erect biennial or perennial with stout taproot. Stems 1 to 4 feet. Basal leaves up to 6 inches long, narrow, undivided to pinnately parted. Leaves of the mature plant finely divided. Flowers with pinkish-purple to cream ray flowers. Phyllaries stiff, tipped with a dark, comb-like fringe. Seeds about 1/8 inch long, tipped with tuft of persistent bristles.
Centaurea stoebe

Squarrose knapweed
Perennial forming dense colonies by shoots from widely spreading black roots. Stems erect, openly branched, up to 3 feet. Lower leaves deeply, but not so finely, divided; upper leaves entire or serrate. Flowers 1/4 to 1/2 inch in diameter, numerous on the ends of branches. Ray flowers pink to lavender. Phyllaries pearly, rounded or pointed, with papery margins. Seeds small, from 1/8 to 1/4 inck long, with numerous whitish bristles. 
Centaurea virgata

 Yellow starthistle
Annual 1 to 3 feet, erect and rigid branching, from taproot. Stems rigid, winged, and covered with a cottony pubescence. Basal leaves deeply lobed (as are leaves of seedlings); upper leaves entire and sharply pointed. Flowers yellow, terminal, armed with straw-colored 3/4 inch thorns. Outer seed dark brown without bristles; inner seed mottled light brown with a tuft of white bristles, about 1/8 inch long.
Cirsium ochrocentrum

Bull thistle
 A biennial with a short, fleshy taproot. The stem is 1 to 6 feet tall, widely spreading and spiny winged. Leaves sparsely and prickly hairy above, cottony below with spines on margins. Lower leaves to 16 inches long. Flowers terminal, solitary to more or less clustered, 1-1/2 to 2 inches wide and dark purple. Phyllaries narrow and spine tipped. Seeds straw colored, 1/8 inch long, striped lengthwise with brown or black, with a protrusion at one end, and tipped with plume-like hairs.
Cirsium vulgare 

 Musk thistle

Carduus nutans

 Scotch thistle

Onopordum acanthium

Mediterranean sage

An aromatic biennial 2 to 3 feet. Leaves large, grayish, woolly, irregularly toothed, develop a rosette up to 2 feet in diameter in the first year. Plant bolts second season producing multi-branched stems with white to blue-green, woolly, felt-like leaves. Flowers two-lipped, usually yellowish-white, borne in clusters on profusely branched stems.
Salvia aethiopis 

Downy Brome
Downy Brome Bromus tectorum L. Poaceae:  Grass Family Downy brome is an annual or winter annual, 4 to 30 inches tall, reproducing by seed.  Leaf sheaths and flat blades are densely covered with soft hair.  Ligules are short.  Inflorescence is dense, slender, usually drooping, 1-sided, 2 to 6 inches long.  Spikelets are nodding, slender 3/8  to ¾ inch long.  Awns are 3/8 to 5/8 inch long, usually purplish at maturity.
Bromus tectorum 

Houndstongue Cynoglossum officinale L. Boraginaceae:  Borage family; Houndstongue is a biennial growing 1 to 4 feet tall and reproducing by seed.  Leaves are alternate, 1 to 12 inces long, 1 to 3 inches wide, rough, hairy, and lacking teeth or lobes.  Flowers are reddish-purple and terminal.  The fruit is composed of 4 prickly nutlets, each about 1/3 inch long. Houndstongue was introduced from Europe.  It forms a rosette the first year, and sends up a flowering stalk the second year.  The leaves are rough and resemble a hound’s tongue.  It may be found in pastures, along roadsides and in disturbed habitats.  In the Alturas Weed Management Area, it is most commonly found in the Big Valley Mountains of Lassen County, within Ponderosa Pine and White Fir plantations.  The nutlets break apart at maturity and cling to clothing or animals.   Houndtongue is toxic, containing pyrrolizidine alkaloids, causing liver cells to stop reproducing.  Animals may survive for six months or longer after they have consumed a lethal amount.  Sheep are more resistant to houndstongue poisoning than are cattle or horses.  Horses may be especially affected when confined in a small area infested with houndstongue and lacking desirable forage.  Therefore, ranges and pastures should be maintained to encourage production of grasses and high quality forage. Non-standard name: gypsy flower
Cynoglossum officinale 

Pheasant Eye


Noxious weeds are non-native plants introduced to North America from Europe and Asia. These plants have spread at an alarming rate because, unlike native species, there are no native insects, fungi, or diseases to control their growth and spread in this country. What began as a handful of plants introduced in the 19th century, now number in the hundreds of millions. Noxious weeds destroy wildlife habitat and forage, threaten endangered species and native plants, increase erosion and groundwater loss and prevent recreational activities.

Estimates indicate that noxious weeds are spreading at rate of 4,600 acres per day on federal lands alone in the western United States.  They have invaded approximately 17 million acres of public rangelands in the West -- more than quadrupling their range from 1985 to 1995. In northern California, yellow starthistle expanded its range from 1 million acres in 1981 to 10 million acres in 1997.

The Bureau of Land Management is just one of many governement agencies mounting an effort to control and prevent noxious weeds, as well as educate the public about how destructive these plants can be.

The information presented here is from the book, Selected Noxious Weeds of Northeastern California, a joint project of the Bureau of Land Management, U.S. Forest Service, Lassen County, Modoc County, Northern Deputy Agricultural Commissioners and Sealers Association, Tuscarora Gas Transmission Company, and the California Department of Food and Agriculture.