ND Noxious & Troublesome Weeds
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Annual
Sowthistle and Spiny Sowthistle (Sonchus oleraceus L.) [Sonchus asper (L.) Hill] |
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State Noxious Weed List -No Growth form: Both species are annual and differ primarily in leaf form. Spiny sowthistle, as the name implies, has sharp stiff prickles along the stem and leaves. Leaves clasp the stem with rounded basal lobes (auricles) that resemble a rams horn.
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Annual sowthistle leaves are deeply toothed lower on the plant but progressively less so on the upper stem and auricles are distinctly pointed. Both species have yellow flowers, borne on a long vase like involucre, with several in a cluster. Spiny sowthistle has slightly larger flower heads (0.5 to 1 inch across) compared to annual sowthistle (0.25 to 0.75 inches). The seeds for both are flattened with 3 to 5 ribs. Both species grow 2 to 4 feet tall. |
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These sowthistle species are both
from Europe and now widely established in the region.
They have a milky latex and a small tap-root. The
plants are often mistaken for perennial sowthistle.
However, perennial sowthistle has a creeping perennial
root system, larger and longer leaves and grows
4 to 6 feet tall. 
