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Chavers Mining Resource <br /> Integrated Noxious Weed Management Plan <br /> January 2024 <br /> Page 4 <br /> ■ Scotch Thistle(Onouordum acanthium): Scotch thistle(Onopordum acanthium)is a <br /> non-native biennial forb that reproduces solely by seed. A biennial is a plant that <br /> completes its lifecycle within two years. During the first year of growth, Scotch thistle <br /> appears as a rosette in spring or fall. During the second year in mid to late spring—the <br /> stem bolts, flowers, sets seed, and the plant dies. A prolific seed producer, Scotch thistle <br /> can produce up to 14,000 seeds per plant. Scotch thistle can grow up to 12 feet tall. Stems <br /> are numerous,branched, and have broad, spiny wings. The leaves are large, green, spiny, <br /> and covered with fine dense hair giving the leaf a woolly appearance. The flowers are <br /> violet to reddish in color,numerous(70-100/plant), and are surrounded by spine-tipped <br /> bracts. You can expect to see flowers from mid-June to September.Due to the robust, <br /> spiny nature of Scotch thistle,this plant can act as a living barbed wire fence, making <br /> areas impassible for wildlife, livestock, and people. Scotch thistle invades rangeland, <br /> overgrazed pastures, roadsides, and irrigation ditches. It also prefers moist areas adjacent <br /> to creeks and rivers. <br /> ■ Hoary Cress (Cardaria draba): Hoary Cress(Cardaria draba)is a non-native perennial <br /> that spreads by seeds and aggressive, creeping,roots that vigorously produce new plants. <br /> Depending on conditions,hoary cress grows to a height of to 2 feet tall. The first <br /> leaves emerge from a crown and are dull gray-green, oblong and often have a slightly <br /> wavy margin. Subsequent leaves are alternate,have short fine hairs and an irregularly <br /> toothed margin. Only the lower leaves have stems, others are stalk-less and clasp the <br /> plant stem with two ear-like lobes. Flowers are fragrant, numerous, small,white with 4 <br /> petals and grow in compact clusters.Hoary cress is a member of the Mustard family. In <br /> the fall seeds germinate and rosettes become established. It frequently flowers in April <br /> and May and again in the fall during optimum conditions. Seed production begins about <br /> one month later. Hoary cress produces up to 4800 seeds per plant. Seed viability is up to <br /> 3 years. However,the primary means of spread is the vertical and horizontal root system. <br /> Root fragments are capable of forming new plants. In one year, a single plant, without <br /> competition, can spread vegetatively to cover an area 12 feet in diameter and can produce <br /> 450 shoots.Hoary cress can be found in disturbed open sites,roadsides, ditches, riparian <br /> areas, grain and vegetable fields. It does especially well in irrigated crops such as alfalfa <br /> and sugar beets. Hoary cress grows well in most soil conditions, including alkaline soils. <br /> However, it does not tolerate shade. <br /> ■ Cheaterass(Bromus tectorum): Commonly referred to as cheatgrass, (Bromus <br /> tectorum)it is also known as downy brome, downy cheat and bronco grass. It is widely <br /> distributed throughout the United States and has been reported to be the dominant species <br /> on more than 100 million acres of the intermountain west. Cheatgrass is unique in that it <br /> occupies a dual role as a serious weed and important early season forage. Cheatgrass can <br /> maintain dominance for many years on sites where native vegetation has been eliminated <br /> or severely reduced by grazing, cultivation or fire. Cheatgrass is a winter annual member <br />