Pineapple Weed, Matricaria discoidea
Plants make an impression in different ways. I love Erigeron karvinskianus (Mexican Fleabane) for its prolific flowers, Gunnera manicata for its giant leaves and Calabrese for its taste.
It is the smell of Pineapple Weed, Matricaria discoidea, that I like. It is usually my first impression of the plant, as I accidentally step on it as I walk along footpaths, pavements or over waste ground. It is a scent that takes me back to childhood and warm summer days in the countryside.
I first knew Pineapple Weed by its older scientific name of Matricaria matricarioides. It also has other English names, including ‘wild chamomile‘, ‘disc mayweed‘, ‘pineapple mayweed‘ and ‘apple virgin‘. It is a member of the daisy family, the Asteraceae, and has a rich smell of pineapple when crushed.
Its close relatives Chamomile and the Mayweeds* (which have a similar smell) have more typical ‘daisy’ flowers, with white ray florets around the outside of the flower head and tube florets in the centre. Pineapple Weed just has the tube florets, which are like small yellow buttons. It is either the plant’s smell or the shape of its flowers that give it the name Pineapple Weed.
Pineapple weed is an annual herb which flowers from June to September in the UK. It is not native to Europe, however, and was introduced to Britain in 1781 from North America. It escaped from Kew Gardens in 1871 and soon spread. In Finland it was first grown in Kaisaniemi Botanic Garden in Helsinki in 1849 but within a year it had escaped and is now found throughout the country.
Pineapple Weed is a native of North-east Asia and the North-west United States. It is usually found growing in poor, compacted soils and roadsides. My nearest patch is on the verge of George Borrow Road in Norwich; I took the photograph above when walking from Bamburgh to Seahouses in Northumberland in June this year.
Pineapple Weed is edible, though some people are allergic to it. The chemical that gives the plant its characteristic fruity smell is a terpene called myrcene, which is also found in Basil, Hops, Mangoes and Cannabis. The plant also contains a coumarin called herniarin, and this may be responsible for the allergic reaction. The chemical has a range of biological activities, including haemostatic and anthelmintic properties (i.e. it can stop bleeding and can be used to expel parasitic worms). Extracts of Pineapple Weed also have antimicrobial properties.
The fresh or dried flower heads of Pineapple Weed can be used to make a herb tea (rather like chamomile) and the fresh flowers can be eaten raw in salads or cooked.
Pineapple Weed’s ribbed seeds can be spread on footwear. However, in “The Roadside Wildlife Book” (1974) and “Flora Britannica” (1996), Richard Mabey suggests that the motor car, and pneumatic tyres in particular, aided the spread of the plant in Britain, as the seeds stick to tyres. He quotes an experiment: in 1968 a car had its tyres carefully washed and was then driven along 65 miles of road following heavy rain, including passing places and field gateways. The tyres were then hosed down and the sediment was incubated in sterilised compost. Plants from 13 different species grew, including 220 seedlings of Pineapple Weed.