The identification of ‘mayweeds’ often causes confusion. They are all members of the daisy family, Compositae, and have a superficially similar appearance. As a result of successive taxonomic revisions they have a large number of synonyms. However, it is crucial to accurately identify the species present in an experiment because the ecology and susceptibility to certain herbicides differs between species.
SYNONYMS
Tripleurospermum inodorum ‘scentless mayweed’ Bayer Code: MATIN
Tripleurospermum maritimum ssp inodora, Matricaria maritima ssp inodora,
Matricaria perforata, Matricaria inodora, Chamaemelum inodorum.
Matricaria recutita ‘scented mayweed’, ‘wild chamomile’, Bayer Code: MATCH
Matricaria chamomilla, Chamomilla recutita.
Matricaria discoidea ‘pineapple weed’, ‘rayless mayweed.’ Bayer Code: MATMT
Matricaria matricariodes, M. suaveolens, M. discoidea, Chamomilla sauveolens
Anthemis arvensis ‘corn chamomile’ Bayer Code: ANTAR
Anthemis cotula ‘stinking mayweed’ Bayer Code: ANTCO
IDENTIFICATION
(For an illustration of the technical terms used here, see the glossary at the end of this leaflet.)
Tripleurospermum inodorum
‘Seeds’: 2-3 mm.long, black, sometimes lighter on the 3-4 sharp angles. Angularly cylindrical with a flat style end.
Seedling: Leaves bipinnate from 2nd or 3rd true leaf.
Leaves: 2-3 pinnate, hairless, bright glossy green.
Smell: Almost none.
Flower head: 2-4cm diameter, yellow centre, white rays never reflexed, receptacle flat and solid. No scales on the receptacle between the seeds.
Ecology: The commonest mayweed of arable crops in England especially on heavier soils. Relatively tolerant of some herbicides used in the 1980s and robust enough to compete with cereals and rape.
Matricaria recutita
‘Seeds’: 1-1.5mm.,dark with strong longditudinal white ridges which make the bulk seed appear grey.
Seedling: First 4 leaves regularly pinnate with pinnae <4 times as long as broad.
Leaves: Hairless, multi- pinnate with long very narrow, linear segments.
Smell: Invariably pleasant.
Flower head: 1-2.5cm. diameter, conical yellow centre, white rays reflexed downward. Receptacle conical, hollow. No scales on the receptacle between the seeds.
Ecology: A less robust plant than T. inodora but more adapted to lighter and drier soils. Its early flowering and short life cycle adapt it well to some horticultural crops.
Matricaria discoidea
‘Seeds’: 1mm. grey with low ridges and oblique style end.
Seedling: First 4 leaves irregularly pinnate with pinnae >4 times as long as broad.
Leaves: Hairless, multi-pinnate with linear segments.
Smell: Not unpleasant in moderation, said to resemble that of pineapples.
Flower head: 1 cm diameter, conical, yellow with normally NO white rays. Receptacle hollow, conical.
Ecology: A low growing species which does not compete with arable crops. Restricted to open grassland and some vegetable crops.
Anthemis arvensis
‘Seeds’: 1.5-2mm.straw coloured, four-sided with a flat base and no tubercles.
Seedling: First two true leaves very regularly pinnate, with leaflets all exactly opposite, in the same plane with no teeth and broader near their tips than near their base.
Leaves: Slightly woolly especially underneath, often with a blue-grey tinge. 1-3 pinnate with narrow but short and flat segments.
Smell: Pleasant when dilute.
Flower head: 2-3 cm diameter, yellow centre, white rays. Receptacle shallowly conical, solid, with scales between the seeds which greatly delay seed shedding.
Ecology: Not very competitive, particularly at the seedling stage. Very susceptible to ‘hormone’ herbicides and now rare in northern Europe.
Anthemis cotula
‘Seeds’: 1.5-2mm., brown, irregularly conical with obvious tubercles on longditudinal ridges.
Seedling: First four true leaves irregularly pinnate with flat, irregularly toothed leaflets more or less in the same plane.
Leaves: Generally hairless but with a grey-green colour. 2-3 pinnate with the segments flat, long and narrow.
Smell: Strong, astringent unless very dilute.
Flower head: 1-2.5cm diameter, yellow centre, white rays become reflexed, receptacle steeply conical in fruit with a few teeth between the seeds near the apex.
Ecology: No longer a common arable weed, now confined to compacted areas and thin crops on headlands.
SOME OTHER SPECIES
Tripleurospermum maritimum ssp maritimum ‘sea mayweed’
This taxon is sometimes considered a separate species to T. inodorum. It tends to be biennial or perennial with somewhat succulent leaves and prostrate habit. It is restricted to maritime habitats.
Tripleurospermum tenuifolium Matricaria trichophylla, Bayer Code: MATTR
Chamaemelum trichophyllum.
Taller than T. inodorum with larger flowers (2-4cm.) and brown rather than black seeds. Restricted to the Balkans.
Anthemis ruthenica A. neilreichii, Bayer Code: ANTRU
Plant profusely branched, densely hairy, leaves simple to bi-pinnate with broad segments. Pleasant citrus smell when crushed. Flower heads 1-2.5cm. diameter, receptacle conical, scales small-toothed, seed cylindrical. Restricted to the Balkans and Asia.
Anthemis altissima A. cota, Cota altissima, Bayer Code: ANTAL
Leaves grey-green, regularly bipinnate. Stem below flower head strongly thickened. Flower 2-4 cm. diameter, receptacle flat, scales long pointed. Seeds brown-black, flattened, ten ribbed. Southern Europe and the Balkans.
Anthemis austriaca A. cotiformis Bayer Code: ANTAU
Very woolly, grey-green, bi-pinnate leaves with short narrow segments. Seeds light brown, flattened, strongly angled. East Mediterranean and Balkans.
