Erysimum officinale L.
It is distinct from the mustard plants which belong to the genus Brassica. S. officinale is similar to other Sisymbrium, but differs in its tall, erect stems with tiny flowers and fruits that are compacted parallel to the stem instead of hanging free. S.officinale grows to 80 cm high. The lower leaves are broad with two or three lateral lobes. The flowers are about 4 mm across and yellow. Fruits are long and without hairs when young but show hairs when mature and reach 18 mm long on racemes pressed close to the stems.
Found in Ireland, Wales and England and also in the highlands of Scotland.  It is found on roadsides, wasteland and as a weed of arable land. A native of Europe and North Africa, it is now well-established throughout the world.
The Greeks believed it was an antidote to all poisons. In folk medicine, it was used to soothe sore throats - indeed one name for it is singer's plant. This plant "grows by our roadsides and on waste ground, where it is a common weed, with a peculiar aptitude for collecting and retaining dust...it is named by the French the 'Singer's Plant,' it having been considered up to the time of Louis XIV an infallible remedy for loss of voice. Jean Racine, writing to Nicolas Boileau, recommends him to try the syrup...in order to be cured of voicelessness." It is "good for all diseases of the chest and lungs, hoarseness of voice...the juice...made into a syrup with honey or sugar, is no less effectual...for all other coughs, wheezing and shortness of breath...the seed is held to be a special remedy against poison and venom." It was "formerly used for hoarseness, weak lungs and to help the voice." Herbalists use the juice and flowers for bronchitis and stomach ailments, among other uses, and as a revitalizer. In Tibetan medicine it is used to repress the symptoms of food poisoning.
- BSBI List 2007 (xls). Botanical Society of Britain and Ireland. Archived from the original (xls) on 2015-06-26. Retrieved 2014-10-17.
- Parnell.J. and Curtis, T. 2012. Webb's An Irish Flora. Cork University Press ISBN 978185918-4783
- Scannell, M.P. and Synnott, D.M. 1972 A Census Catalogue of the Flora of Ireland Dublin Stationery Office
- Clapham, A.R,. Tutin, T.G. and Warburg, E.F. 12968 Excursion Flora of the British Isles Cambridge University PressISBN 0521046564
- "Plants for A Future Database - Sisymbrium officinale". Plants for a Future database. Retrieved 2007-05-25.
- M Greve & C F Leyel, A Modern Herbal, UK: Merchant Books, 1973, p.570
- N Culpeper, The Complete Herbal, UK: Wordsworth Editions, 1995, p.177
- R C Wren, Potter's New Cyclopedia of Botanical Drugs and Preparations, UK: C W Daniel Co, 1994, p.140
- Howard, Michael. Traditional Folk Remedies (Century, 1987), p.153
- Medical Thangka