Authors: TunyaLee Morisawa, Global Invasive Species Team, The Nature Conservancy
Salsola kali L.
Russian thistle, tumbleweed, common saltwort, windwitch and prickly glasswort
Considered very invasive, Salsola kali competes with native species and obstructs stream channels, roadways, and can become a fire hazard. Salsola kali is a host plant of the sugarbeet leafhopper. This insect vectors curly-top virus, a disease affecting sugar beets, tomatoes, and beans. Salsola kali dominates areas during drought conditions or when competing vegetation is removed. Growth of russian thistle is suppressed when other plants establish first and have adequate moisture to overtop the weed.
Salsola kali is a member of the Chenopodiaceae (goosefoot or beet family) and is native to Russia and Siberia. In 1873, Russian thistle was brought to the U.S. in contaminated flax seed. Prevalence in the semi-desert range of western states is due to its drought tolerance and long-distance method of seed dispersal.
Mature plants grow 31-152 cm high and are bushy, dense annuals. Young plants have stems with red or purple stripes. The 1.3 - 6.4 cm long leaves are alternate, thread-like, cylindrical or awl-shaped with pointed tips. The flowers are solitary, small and greenish to white in color and lack petals. Papery spine-tipped bracts are present at the base of each flower. Russian thistle typically blooms from July to October. However, this plant is indeterminate and continues to flower and produce seed until temperatures drop below -3.9° C.
Salsola kali is a summer annual that reproduces by seed. Fruit contains a single seed and has 5 wings - one from the back of each sepal. When the plant is mature it breaks off at the ground forming “tumbleweeds” that are tossed by the wind, scattering seeds. A single plant can produce 100 - 200,000 seeds. Little moisture (0.25-0.76 cm of rainfall) is required for germination. Seeds are dormant over winter allowing the seed to germinate in spring over a wide range of temperatures (optimum temperatures ranging from 7.2° C to 35° C) generally in late March or early April. Seed longevity is short and rapidly declines after 2 years in the soil. Germination can occur if daytime temperatures are above freezing, however, seedlings are easily killed by frost. Seedlings look similar to pine tree seedlings. A large, spreading root system, 183 cm laterally and 183 cm deep, enables plenty of shoot growth with little moisture.
Salsola kali is found in disturbed areas such as roadsides, trails, abandoned fields, along streams and lakes, and over-grazed ranges and pastures.
Establish desirable plants such as competitive perennial grasses in disturbed or open areas and after the control of russian thistle.
Pull or uproot young plants or hoe just below ground level before seed set. Cutting flowers before maturity has worked for some stewards on preserves.
Mowing Salsola kali tends to cause the plant to grow low but repeated mowing may provide control.
Some plants in the Pacific Northwest are resistant to sulfonylurea herbicides such as Glean®, Finesse®, Ally®, Amber®, Express® and Harmony Extra®. Resistance to the trazine herbicides has also been observed.
A non-selective broadleaf herbicide such as glyphosate can provide control of Salsola kali. Apply the herbicide before seed set. An application of 2,4-D may actually cause S. kali to become tough and leathery, producing a plant that is more difficult to manage.
Pacific Northwest Extension Publication, Washington, Idaho, Oregon. Russian Thistle (Salsola iberica Sennen & Pau). Weeds Publication PNW 461.
Pacific Northwest Extension Publication, Washington, Idaho, Oregon. Managing Russian Thistle Under Conservation Tillage in Crop-Fallow Rotations. Weeds Publication PNW 492.