Marsh Sowthistle, Sonchus palustris, by the River Yare.

If you visit the Norfolk Broads or the coastal wetlands of Suffolk you may encounter a tall, stately plant with yellow flowers growing in the marshes and on some of the riverbanks. This is Marsh Sowthistle, Sonchus palustris.

Marsh Sowthistle (also known as Fen Sowthistle) is a perennial plant. It has long, lance-shaped leaves with two backward-pointing lobes at the base. In late spring the plant produces tall stems which can reach 2.5 or even three metres (8 – 9.5 feet) tall, each one bearing many-branched bunches of yellow flowers. Flowers are produced from May to September but usually peak in late July and early August. They are followed by seeds with fluffy white parachutes, which are dispersed by the wind.

Sonchus palustris flower and buds.

Sonchus palustris flowerhead with some seeds forming.

Sonchus palustris is a member of the Daisy family, Asteraceae (formerly known as the Compositae) and each flower head is a composite structure consisting of lots of individual small flowers (florets). Yellow-flowered Asteraceae can be difficult to identify but Sowthistles are some of the easiest and Marsh Sowthistle is pretty impossible to confuse with any of its relatives because of its sheer size (note 1).

Sonchus palustris has a restricted range in the British Isles. It is absent from Scotland and Ireland and the native populations are in the Norfolk Broads and East Suffolk (where the plant is increasing in number) and the Thames valley and North Kent (where urban development has caused a decline). A population of plants found in Hampshire in 1959 is also thought to be native.

The original populations of Marsh Sowthistle in Cambridgeshire became extinct through drainage long before 1930 but the plant was reintroduced to Woodwalton Fen in Huntingdonshire and has now spread out along the River Nene and drainage channels in the Fens. Marsh Sowthistles by the Humber in Yorkshire were probably introduced with willows from East Anglia. There is also a small colony of Marsh Sowthistle in Bedfordshire and a single site in Wales.

Outside the British Isles, Sonchus palustris is a native of much of Europe, east into Turkmenistan, Uzbekistan and western Russia, reaching as far south as Iran, Turkey and Spain. It is absent from Portugal and Finland and became extinct in Italy. Sonchus palustris has been introduced into Ontario in Canada, where it occurs at two widely separate sites (note 2).

In Norfolk, two of the best places to see Marsh Sowthistle are Strumpshaw Fen RSPB Reserve and the Ted Ellis Reserve at Wheatfen, where walking along a path lined with magnificent Marsh Sowthistle plants is one of the highlights of any visit in July and August.

Marsh Sowthistles, Great Willowherb and Common Reed at Wheatfen. 8th August 2022.

Marsh Sowthistle featured at a key moment in the lives of Ted and Phyllis Ellis, who lived at Wheatfen and  studied plants, fungi and wildlife throughout their lives. Phyllis studied Botany as part of her teaching diploma and in 1934 she was observing Marsh Sowthistles on St. Olave’s Marsh (by the River Waveney). Ted was also on site and noticed her interest in the plants. He approached her, thinking that she might be up to no good, possibly about to dig up the plants. This is said to be the first time they spoke; they married four years later (note 3).

Marsh Sowthistles were much rarer in Norfolk in the 1930s. In 1957, in one of his nature columns, Ted Ellis attributed the increase in plants to the dredging of waterways, where the dredged spoil on riverbanks provided an ideal place for Marsh Sowthistle seeds to germinate (note 3).

Sowthistles have hollow stems containing a white latex that bleeds when they are cut or broken. Their English name comes from the practice of feeding sowthistles to lactating sows in the belief they would produce more milk. Sonchus means “hollow” and palustris refers to the damp ground where Marsh Sowthistle grows.

In general, sowthistles are edible and the young leaves can be eaten raw or cooked and contain good levels of vitamins A, B, C and K, but old leaves are bitter and tough. There are some sowthistle recipes on the Eatweeds website.

Sowthistles also had various medicinal uses: the latex was used as a cure for warts and parts of the plants were used to hasten childbirth, treat skin and eye problems and freshen foul breath. The Plants For A Future website has specific entries for the food and medicinal uses of Prickly Sowthistle (Sonchus asper) and Smooth Sowthistle (Sonchus oleraceus). As always there is the caveat: “Always seek advice from a professional before using a plant medicinally.”

But it’s best to stick to Prickly Sowthistle (Sonchus asper) and Smooth Sowthistle (Sonchus oleraceus) if you’d like to add sowthistles to your diet. Marsh Sowthistles should be admired rather than eaten.

Notes

Note 1 – Mike Crewe’s Flora of East Anglia website gives a useful comparison of the yellow-flowered Asteraceae that grow in East Anglia.

Three other species of Sonchus (Sowthistles) occur in the British Isles and the Botany In Scotland blog has a post on how to tell them apart. Prickly Sowthistle (Sonchus asper) and Smooth Sowthistle (Sonchus oleraceus) are both annual plants, found on disturbed ground such as in gardens and on roadsides and the edges of arable fields. Perennial Sowthistle (Sonchus arvensis) also grows on waste ground but also on river banks and ditches at the coast. All three grow to 1.5 metres tall, much shorter than Marsh Sowthistle.

My favourite of the three is Perennial Sowthistle, which I tend to call Corn Sowthistle, the name I learnt from my first flower book, Keble Martin’s Concise British Flora in Colour. (Keble Martin used “Fen Sowthistle” as the English name for Marsh Sowthistle but it wasn’t a plant I’d seen.)

For completeness, the “New Flora of the British Isles“ by Clive Stace (Fourth Edition, 2019) also lists a hybrid between S. oleraceus and S. asper which has occurred very rarely in England but “most records [are] doubtful or erroneous” and Slender Sowthistle (Sonchus tenerrimus), a rare casual from Southern Europe.

There are 106 species of Sonchus worldwide.

“Sowthistle” is sometimes spelt “Sow-thistle”.

Note 2 – The Plantnet website also shows some occurences in the United States, eastern Africa and eastern Australia, but the Kew Plants Online website makes no mention of these.

See the INPN website for the distribution of Sonchus palustris in France.

Note 3 – From the Ted Ellis Trust booklet “Wildflowers of a Broadland Reserve Wheatfen. Part 1: Species of the fen and reedbeds”, written by Will Fitch, the current warden of Wheatfen.

Phyllis Ellis died in 2004 but I was fortunate to meet her in the late 1990s when I took part in a conservation task at Wheatfen. She was very hospitable and invited us in to have tea and cake in her living room.