Identifying Sow Thistle (Sonchus oleraceus)

Take great care when identifying wild plants and fungi, this blog is not a resource to be taken by itself and further resources will be linked. Consult other sources and double check. While foraging is an extremely rewarding and useful skill, numerous common plants and fungi can make you sick or kill you. Be absolutely sure of what you’re eating and, when gathering, ensure you leave enough not only to ensure the survival and growth of the species but also enough for others to enjoy, from the human and more-than-human communities. Also cultivate an awareness of contamination and pollution – wastewater runoff, spraying, exhaust fumes – as this should affect your decision to harvest.

The Plant

Sonchus oleraceus is an annual edible “weed” from the Asteraceae family. It is native to Europe and Western Asia but is now considered an invasive species throughout the world, especially in Australia and New Zealand. It can be found in most disturbed areas such as gardens, public parks, riversides, fields, and orchards, and grows well in full sun but can tolerate most soil conditions. Sonchus means “hollow” referring to sow thistles hollow stem, whilst oleraceus means “vegetable/herbal”, describing its use to people for hundreds of years. Its common name “sow thistle” came about due to the plants attractiveness to pigs and “thistle” comes from the Proto-Indo-European word for “to prick”, as quite a few Asteraceae’s have sharp prickles. There was a native variety of Sonchus oleraceus called Sonchus kirkii (named after several naturalists named Kirk), which the indigenous Māori called “pūhā”. This native thistle is scarce due to colonisation and so now Māori often eat this common sow thistle instead and refer to it as pūhā.

Description

Sow thistle stems are hollow, green (sometimes purple or flecked with purple), and grow upright form 30- 100cm high. Sonchus oleraceus leaves are a medium green to a dusky blue green and are jagged in shape (I find the leaves on the same plant often look quite different from one another). The leaves are often matte but are sometimes more waxy and shiny (these ones are thicker and firmer leaves). When the foliage or stem is crushed it exudes a milky white sap which is very bitter. Sow thistle flowers are bright yellow, composite, and tend to grow in clusters near at the very top of the plant. They will produce flowers during spring and summer and they are hermaphroditic, meaning each flower contains male and female parts which are pollinated by insects. The seeds are like fluffy parachutes which are carried by wind or water.

Ecology

I have been fortunate enough to come across Sonchus oleraceus all over the North and South Islands on New Zealand. It will generally crop up in sunny spots in disturbed areas such as; vegetable gardens, parks, pastures, walkways, roadsides, and riverbanks. It prefers full sun and tolerates most soil conditions and is at its tastiest when you harvest the fresh new growth in spring and summer. Sow thistle is available to harvest pretty much all year round, however.

Nutritional/Medicinal Information

Sow thistle is high in a number of nutrients, especially vitamin C as it contains 30-40mg of vitamin C per 100g of thistle. It also contains vitamins A, B1, B2, and a fair amount of the mineral calcium.

This bitter green is good for liver health, digestive function, and as a blood purifier. A juice was made from sow thistle and drunk to treat haemorrhages and the Native American Houma people used an extraction of the plant as an abortifacient; to bring on menstruation and to also expel the placenta after birth. The sap can treat constipation and also be applied topically to prevent infection of wounds.

Māori would thicken the sap and use it as a kind of chewing gum.

Possible Lookalikes

Sow thistle is most likely to be confused with prickly sow thistle (Sonchus aster), which, as it’s name implies, is prickly and spiny along the leaf edges. This plant is also edible, however.

The native Sonchus kirkii is also edible but is less common and not as easy to forage.

Dandelions and hawksbeards don’t look as much like sow thistle but they are also edible incase of confusion.

Interesting Facts

Māori would thicken the sap and use it as a kind of chewing gum.

Sow thistle was not only popular among pigs just as food, it is also believed that the latex-like milky sap in the plant was helpful for lactation in pregnant sows.

If you do want to get rid of this plant in your garden, for whatever reason, it can generally be controlled by mowing as it doesn’t regrow from the root.

Storage and Cooking

Sow thistle is best harvested young and eaten fresh. You can eat the leaves chopped up fresh or, if the bitterness puts you off, you can bruise and rinse handfuls of the leaves under running water and rinse out some of the sap, then chop and add to cooked food. The roots can be dried and used as a coffee substitute.

Sonchus oleraceus is a great addition to salads, soups, stirfries, pastas, curries, pizzas, or juices. Anything you would use spinach in, I would recommend trying sow thistle instead. Enjoy my fellow foragers!

Further Reading

Herb Federation of New Zealand

Wild Food UK

Massey University

iNaturalist

Manaaki Whenua Land Research