S. oleraceus is an annual and sometimes biennial herb, 40-150 cm tall, containing white latex in all plant parts. The taproot is upright with many branches, especially near the soil surface. Stem below synflorescence simple or branched, glabrous. Basal and lower stem leaves with basal portion petiole-like and attenuate, mostly smaller than middle stem leaves, otherwise similar. Middle and upper stem leaves extremely variable, elliptic, oblanceolate, or lanceolate, 6-20 × 2-9 cm, almost entire to ± irregularly, soft, glabrous, adaxially dull green, base auriculately clasping with auricles usually acutely prostrate, margin ± coarsely spinulosely dentate, apex acute;lateral lobes triangular to elliptic, usually recurved, apex acute to acuminate;terminal lobe larger than others, broadly triangular, broadly hastate, or obovate-cordate. Synflorescence shortly corymbiform or racemiform, with few to several capitula. The flower-head has a green involucre consisting of 27-35 lance-shaped bracts, 10-13 mm long and hairy while young. Each flower-head contains 80-250 ligulate flowers which are longer than the involucre. The flowers are yellow and the ligule is about as long as the corolla tub. Achenes are brown, 2.5-3.75 x 0.7-1 mm, oblanceolate, and transversely tuberculate-rugose. Thistledown is white and persistent. One plant may produce 4000-6000 seeds or more (Nyárády, 1965;Anghel et al., 1972;Boulos, 1976;Hutchinson et al., 1984;Ciocârlan, 1990).
Related invasive species
- Sonchus oleraceus
Related Farm Practice
- Hosts
- Soil
S. oleraceus is a common seed crop contaminant and has been carried either deliberately or accidentally by humans to almost every corner of the earth, where it invades mainly open and disturbed areas. It grows in a wide variety of environments on a wide range of substrates – roadsides, cultivated land, gardens, construction sites, sand dunes, logged or burned areas, on walls, mountain slopes, and near water. Once introduced to a new area the plants spread quickly because they grow and flower quickly and produce copious wind- and bird-dispersed seeds that germinate quickly in large numbers. They invade many cropped areas, especially among vegetable and winter crops. They are almost perfect ‘designer weeds’. Additionally, this species has small light seeds which are easily dispersed by wind and water.
S. oleraceus may occur as a weed in annual or perennial crops, particularly those which are widely-spaced or have a longer vegetation period, such as Helianthus annuus, Nicotiana tabacum, Arachis hypogaea, Phaseolus vulgaris and Citrullus lanatus. S. oleraceus competes with cultivated plants during fructification, and thus has a detrimental effect on yield (Holm et al., 1977). S. oleraceus grows well in optimally interspaced maize crops (Lorenzoni, 1963).