Sonchus asper

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.

Descriptions

Characteristic Features

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 Plant

Young leaves form a basal rosette. Both young leaves and cotyledons have a whitish coating.

Cotyledons

Egg-shaped, approximately 3 to 8 mm (0.12 - 0.31 inch) long, occur on petioles.

Stems

Erect, 25 cm - 150 cm (9.84 - 59.05 inch) tall, branched in the inflorescence.

Leaves

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.

Propagatio Organs

Flowers

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.

Flowering Period

May - October.

Fruit

Pappus of numerous capillary bristles to 9 mm (0.35 inch) long, white. Receptacle slightly concave in flower.

Viability Of Seeds

1-2 years

Propagation

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.

Occurrence

Habitat

Waste ground, disturbed sites, roadsides, railroads.

Soil

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.

Agricultural Importance

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.

Control

Integrated Crop 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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