Weeds

Sonchus arvensis L.- Perennial sowthistle

Taxonomy:

Family Asteraceae Dumort. (Compositae), Genus Sonchus L. Only one subspecies is described in the territory of the Former Soviet Union - Sonchus arvensis subsp. uliginosus (Bieb.) Nym.

Biology type:

Soboliferous perennial

Morphology and biology:

Roots are long, well developed, with adventitious buds. Root system is shallow. Main root does not reach a depth of more than 50 cm. Long horizontal roots branching off this root elongate more than one meter in length, although they lie no deeper than 6-12 cm. Root system is very fragile, and even small root fragments (up to 3 cm in length) are able to produce sprouts. Propagation of this weed in crops is due to the formation of root offsets. Stem is upright, in upper part it is adenotrichous or glabrous. Leaves are lance-pinnate with triangular lobes; near their base there are rounded auricles. Upper leaves are entire. Inflorescences are rather large flower heads, up to 3 cm across when open. It flowers from July till September. Achenes are oval, flattened, 2.5-3 mm in length, 0.75-1 mm in width and 0.4 mm in thickness. They are dark-brown, blunt-rounded on the top, narrowed to the base, with 5 rather prominent longitudinal ribs. Pappus from white soft simple hairs easily separates from achenes.

Geographical range:

This weed occurs across almost all Europe and northern Africa. As an adventive plant it is found in America, Australia and Japan. Within the territory of the Former Soviet Union it occurs throughout the European part, in the Caucasus, in the southern part of Western and Eastern Siberia, in the northern part of Central Asia, and in the Far East.

Ecology:

Widely distributed segetal weed in fields of forest zone in the European part of the Former Soviet Union. It needs sufficient moisture, and in dry fields it usually occupies lower, wet places. This weed is able to grow in moisture conditions ranging from meadow and steppe, to marsh. It prefers rich soils, but is able to tolerate weak salinity. Its importance as an arable weed in steppe zone is reduced, and in desert zone (even in irrigated fields) it does not grow.

Economic value:

One of the worse weeds in our fields. It infests all types of crops, and also occurs in fallows, vegetable and fruit gardens. All plants contain white sap not palatable to cattle. It is regarded as a good bee plant. Control measures: the main requirement is weed eradication no later then rosette stage, when newly formed root system is not able to vegetatively propagate.

Reference citations:

Buch T.G., Kachura N.N., Shvydkaya V.D., Andreeva E.R. 1981. Weeds of Primorskiy Krai and their control measures. Vladivostok: Dalnevostochnoe Publishing House. 256 pp.
Kott S.A. 1955. Weed plants and their control measures. Moscow: Selchozgiz. Ed.2. 384 pp.
Maltsev A.I. 1937. Atlas of the major species of weeds of the USSR. Moscow-Leningrad: Selkhozgiz. V.1: 168.
Nikitin V.V. 1983. Weeds in the flora of the USSR. Leningrad: Nauka. 454 pp.
Ramenskiy L.G., Tsatsenkin I.A., Chizhikov O.N., Antipin N.A. 1956. Ecological estimation of forage land on a plant cover. Moscow: Selkhozgiz. 472 pp.
Tcherepanov S.K. 1995. Vascular plants of Russia and adjoining states (within the limits of the Former Soviet Union). Saint Petersburg. 991 pp.

© O.E.Kravchenko