T.E.R:R.A.I.N - Taranaki Educational Resource: Research, Analysis and Information Network

Sonchus arvensis (Field sow thistle)

Kingdom: Plantae
(unranked): Angiosperms
(unranked): Eudicots
(unranked): Asterids
Order: Asterales
Family: Asteraceae
Tribe: Cichorieae
Genus: Sonchus
Species: S. arvensis
Binomial name: Sonchus arvensis
Common names: Field sow thistle, Perennial sow thistle, Field milk thistle, Corn sow thistle, Dindle, Gutweed, Swine thistle, Tree sow thistle, Puha

There are four species of Sonchus called puha whose leaves are eaten as salad greens or cooked like spinach. Sonchus oleraceus (Common sow thistle), Sonchus asper (Prickly sow thistle), Sonchus arvensis (Field sow thistle) Sonchus kirkii  (New Zealand sow thistle)

Sonchus arvensis is a perennial wildflower 50–150 cm tall native to Europe and has also become naturalized in many other countries and is considered an invasive noxious weed in some places including New Zealand in Otago, Canterbury and Hawkes Bay. Its habitats are paddocks, ditches, roadsides, edges of gravel parking lots and disturbed areas. 
Sonchus arvensis has golden yellow flowers are 4 cm wide and are surrounded by involucral bracts. The bright yellow of the flowers attracted bees and flies which aid in successful pollination, this can result in the production of up to 6,000 flying-haired achenes, which help it spread with ease. The achenes are also spread with grain and hay-seed. Sonchus arvensis first grows a leaf rosette with creeping roots which have adventitious buds which develop into new shoots. 
The plant has a copious amount of latex hence the word ‘milk’ used in some of its common names.

Glandular hairs are present.

Thanks to Wikipedia for text and information