Weed of the Week: Sow Thistle (Annual & Perennial)

Many growers make no distinction at all between perennial and annual sow thistles. That’s because all three versions are tall weeds with yellow, dandelion-like flowers and stems that produce a milky sap. Seedlings of the two species(Sonchus asper & Sonchus oleraceus) are practically indistinguishable, and may be difficult to tell apart even at spray stage without examining the root system. Spiny sow thistle was covered in the previous post.

Annual Sow Thistle: (Sonchus oleraceus L.)

Annual Sow Thistle

Annual Sow Thistle

Winter annual broadleaf plant. Inhabits agricultural land and other disturbed locations. Species are not easy to distinguish at the seedling stage. Mature plants are erect with a smooth thick stem that secretes a milky sap when cut. The leaves are hairless somewhat bluish green. The upper leaves are smaller than the lower leaves. Flowering generally takes place in the spring and summer and under favorable conditions. Flowers cluster at the stem tips to form daisylike flower heads. Flower heads mature into white, fluffy seed heads.


Perennial Sow Thistle: (Sonchus asper L.)

Perennial Sow Thistle

Perennial Sow Thistle

Perennial broadleaf plant. Adapted to a wide range of conditions, perennial sow thistle does best in moist, fertile soils with full sunlight. Stems are upright and leafy at the base. Cut stems secrete a milky sap. Leaves are alternate and waxy, with prickled edges and variable shape. Leaf color varies from light to dark green. Flowers are small, yellow and dandelion-like. They are grouped in loose clusters at the ends of stems. One plant may have up to 20 flower heads, but with only few in bloom at a time.


Select Herbicide Options:


2, 4-D


Grazon P+D


Chaparral (for bermudagrass pastures, will destroy bahiagrass)

Cimarron Max (for bermudagrass pastures, will destroy bahiagrass)

Pastora (for bermudagrass pastures, will destroy bahiagrass)

REMEMBER: THE LABEL IS THE LAW!  Always read the pesticide label before using.




Comments are closed.