The "Dirty Dozen"
Of the 47 listed noxious weeds in Nevada, 12 are particularly troublesome in the Truckee Meadows. Many of them are perennials, or plants that grow back from the roots each year. Click on their names to view their descriptions and photos.
For more information, download the following publications from the University of Nevada Cooperative Extension website:
- Identification of Knapweeds and Starthistles in Nevada
- Identification of Thistles in Nevada
Canada Thistle
Cirsium arvense
- A perennial that spreads by roots and seeds
- Grows 1 to 4 feet tall
- Has clusters of small, white to purple flowers at the end of the stems
- Leaves are very spiny - it hurts to touch this weed!
- Grows in moist and disturbed sites
- This invasive weed is very aggressive and difficult to control
- Pulling and burning do not control this weed, as they favor root resprouting
- Chemical controls are needed
Dalmatian Toadflax
Linaria dalmatica
- A perennial that spreads by roots and seeds
- Grows up to 3 feet tall
- Has yellow flowers that resemble snapdragons
- Leaves are heart-shaped and clasp the stem
- Grows along roadsides and in rangelands or pastures
- In the past, this weed was intentionally planted in gardens, but has now escaped and is very difficult to control
- Pull or dig for several years, removing as much root as possible.
- Mowing is not effective and may spread the weed
- Chemical controls are available
Hoary Cress
Cardaria draba
- A perennial that spreads by roots and seeds
- Grows up to 2 feet tall
- Produces white flower clusters with flat tops in May
- Leaves are lance-shaped and bluish-green
- Grows in meadows, fields, roadsides, ditches, streams, and rangelands as well as garden sites
- Mow two to three times per year at the bud stage to slow spread
- Do NOT pull, as plants will grow from root fragments
- Chemical controls are available
Medusahead
Taeniatherum caput-medusae
- An annual grass that sprouts from seed only
- Grows to 2 feet tall
- Produces a spike flower with long, twisted awns
- Grows in many of the same locations as cheatgrass
- Concentrates silica in the foliage, making it unpalatable to wildlife and livestock
- Burns readily and increases fire danger.
- Control by preventing seed set. Mow or pull when plants begin to flower.
- Chemical controls are available
Musk Thistle
Carduus nutans
- A biennial thistle that sprouts from seed only
- Grows to seven feet tall
- Produces a single, large purple flower at the end of a bent, naked stem
- Leaves have spiny margins
- Stems are spiny and winged
- Grows in varied locations, from vacant fields to roadsides to forest and rangelands
- Dig, removing the top two inches of root prior to seed set
- Chemical controls are available
Perennial Pepperweed/Tall Whitetop
Lepidium latifolium
- A perennial that spreads by roots and seeds
- Grows to six feet tall
- Produces white flowers resembling baby's breath in June
- Leaves are lance-shaped
- Grows along streamsides, meadows, pastures, floodplains, and roadsides and forms dense colonies
- Do NOT pull, dig, or cut the roots, as this may stimulate new growth
- Chemical controls are needed
Purple Loosestrife
Lythrum salicaria
- A perennial that spreads by roots and seeds
- Grows up to six to eight feet tall
- Produces a spike of showy purple flowers in August
- Stems have square edges
- In the past, this weed was intentionally planted in gardens, but has now escaped and is very difficult to control
- Grows in moist or marshy sites along streams or ditches, and in wetlands
- Do NOT pull, dig, or cut the roots, as this may stimulate new growth
- Chemical controls are needed
Russian Knapweed
Acroptilon repens
- A perennial weed that spreads by root and seed
- Grows two to three feet tall
- Produces small pink, white, or lavender flowers during summer months
- Upper part of root is dark brown to black in color
- Grows in dense colonies along roadsides, riverbanks, and ditches, and in pastures and waste places
- Cut or mow prior to seed set to reduce current year's growth; will not kill plants
- Chemical controls are needed
Scotch Thistle
Onopordum acanthium L.
- A biennial weed that spreads by seed only
- Grows up to 12 feet tall
- Violet to reddish flowers are 1 to 2 inches in diameter
- Stems have broad, spiny wings
- Plant has a grayish appearance and is very spiny
- Grows in along roadsides and in waste places and disturbed soils
- Dig, removing the top two inches of root prior to seed set
- Chemical controls are available
Saltcedar/Tamarisk
Tamarix species
- A perennial weed that spreads by root and seed
- Grows as a shrub or deciduous tree; may be 5 to 20 feet tall
- Produces delicate pink to white flowers during spring or summer
- Leaves are tiny and resemble cedar leaves
- Grows in dense colonies along riverbanks, and ditches; a mature tree may use as much as 200 gallons per day
- Weeds will resprout vigorously if cut or burned
- Chemical controls are needed
Spotted Knapweed
Centaurea maculosa Lam.
- A biennial to short-lived perennial weed that spreads by seed only
- Grows one to three feet tall, sometimes taller
- Produces small pink, white, or lavender flowers during summer months
- Bracts below flower head have dark spots but are not spiny
- Grows in disturbed soil, rangelands, pastures, meadows and roadsides
- Cut or mow prior to seed set to reduce current year's growth, or dig, removing the top 2-6 inches of root
- Chemical controls are available
Yellow Starthistle
Centaurea solstitialis
- An annual to short-lived weed that spreads by seed only
- Grows one to three feet tall
- Bright yellow flower heads are about 1 inch in diameter
- Inch-long spines form at ends of bracts under flowerheads
- Stems are winged, but not spiny
- Grows along roadsides and in waste areas and grasslands
- Pull, dig or mow at first sign of yellow flowers
- Chemical controls are available
