Sow thistle is a soft, slightly fleshy, leafy annual. The winter-growing rosette sends up a leafy stem up to 1m tall, with milky sap and yellow flowers about 2 cm in diameter
Leaves are sharply pointed but are never prickly
Flower heads are pale yellow, composite, up to 2cm across, in clusters of a few or many
Leaves on the flower stem alternate on two sides of the stem and are soft, mid- to dark-green and are hairless. Leaves are flat or slightly wavy and are divided nearly to the midrib into sharp, regular lobes. The basal lobes of the stem leaves are sharply pointed and spreading, and the terminal lobes are broad and pointed. Arrow-shaped ear-like projections wrap around the stem at the base of the leaf stalks
Flower stems are erect, hollow, finely ribbed and hairless, leafy, branched and have milky sap
Plants are found throughout New Zealand, in a wide range of places including gardens and disturbed ground, cultivated fields, waste areas and grasslands
Prickly sow thistle is similar in most respects except the leaves are tougher and have prickly spines on the lobed leaves and the flowers a more golden yellow. It can also be an annual or biennial plant.
Biology
Origin
These species are very widespread, found in Europe, North Africa and in north and west Asia, and has been introduced to many other parts of the world.
Life cycle
Both sow thistles are prolific producers of seeds and a single plant can produce up to 25,000 seeds
Each seed has a pappus (feathery attachment) which helps it to be carried for some distance by air currents
Seeds like to germinate on or near the surface and can germinate at any time of the year if soil moisture is adequate. Seeds can survive in the soil for at least a year or two
Plants first produce a low-growing rosette which, in the spring, sends up a flowering shoot.
Benefits
Sow thistle is widely used as a source of food for both livestock and people. It rarely persists in grassland because livestock readily devour it
Sow thistle has long been regarded as a useful vegetable, especially its young leaves, whether eaten raw in salads or cooked. In New Zealand it is known as puha
Due to its nature, prickly sow thistle is less favoured for food.
Impacts
Impact on pasture
This weed has very little effect on pasture as it is readily grazed by stock
Impact on crops
this weed can grow into a tall, bushy plant, but is easy to control by mechanical or chemical means
Control
Grazing Management
Readily grazed by cattle
Physical control
Easily controlled mechanically and, when young, easy to pull or hoe out.
Chemical control
Readily controlled by all commonly used herbicides except trifluralin
Popay I, Champion P, James, T 2010. An illustrated guide to common weeds of New Zealand. New Zealand Plant Protection Society, Christchurch, New Zealand. 416 p.
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