|Scientific Name||Sonchus asper (L.) Hill|
|Common Names||English: Spiny sowthistle, Prickly sowthistle; German; Raue Gänsedistel; French: Laiteron épineux; Spanish: Cerraja, cardimuelle; Portuguese: Serralha espinhosa, serralha áspera|
|Description||Herbaceous annual plant which can reach 150 cm (59.05 inch) in height. It forms a deep taproot.|
Leaves with prickly margins that initially develop as a basal rosette and then occur alternately along the flowering stem, bluish-green color of the leaves, and yellow flowers with a 'puff-ball' seedhead.
Young leaves form a basal rosette. Both young leaves and cotyledons have a whitish coating.
Egg-shaped, approximately 3 to 8 mm (0.12 - 0.31 inch) long, occur on petioles.
Erect, 25 cm - 150 cm (9.84 - 59.05 inch) tall, branched in the inflorescence.
Alternate, sessile, clasping, auriculate, with undulate spiny margins, deep shiny green above, glaucous below.
Lowest leaves obovate to spatulate or somewhat lyrate-pinnatifid, to +15 cm (5.9 inch) long.
Upper leaves reduced, becoming ovate-lanceolate.
Auricles spiny but round at the apex.
Terminal loose corymbiform cluster. Cluster subtended by foliaceous bracts.
Peduncles long, glaucous, occasionally with sparse glandular pubescence but typically glabrous.
Small scarious bracts usually present at the divisions of the inflorescence or somewhere on the peduncles.
Involucre - to 1.5 cm (0.59 inch) tall (long), +/-1cm (0.39 inch) in diameter at base, vase-shaped.
Phyllaries imbricate. Outer phyllaries with small prickles at apex, shorter than inner phyllaries. Inner phyllaries in 3 or 4 series, to 1.5 cm (0.59 inch) long, glabrous, innermost with scarious margins or completely scarious, linear.
Ray flowers perfect, fertile.
Flower heads to 2.7cm (1.06 inch) broad.
Ligules to 6 mm (0.24 inch) long, 1.5 mm (0.59 inch) broad, 4-notched at apex, yellow.
Corolla tube pubescent, 1cm (0.39 inch) long, white.
Style bifurcate, pubescent.
Achenes slightly flattened, ovoid to narrowly so, to 3 mm (0.12 inch) long, 1.1mm (0.043 inch) broad, with 3 nerves on each side (6 total), glabrous.
May - October.
Pappus of numerous capillary bristles to 9 mm (0.35 inch) long, white. Receptacle slightly concave in flower.
Viability of Seeds
By wind-dispersed seed. The average number of seeds per flower head is 200, and a plant often has over 100 flower heads. Seed numbers per plant range from 21,500 to 25,000 but a large plant may produce 60,000.
Waste ground, disturbed sites, roadsides, railroads.
Most soils but S. asper prefers well drained slightly acid to alkaline soils, and has some tolerance of saline conditions.
Additional Crop Information
Also in grass seed production, pasture.
Because of the long pappus of the fruits, this plant can spread easily and quickly. The prickly leaves and big taproot make the plant difficult to remove.
Useful non-chemical contribution to Integrated Weed Management
Cutting, pulling or hoeing of the plants before flowering. Tillage and surface cultivations in spring and the inclusion of root crops in the rotation should keep the weed in control. Regular cultivations will help to deplete the soil seedbank.
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