Constant species

Capsella bursa-pastoris, Chamomilla suaveolens, Lolium perenne, Poa annua, Polygonum aviculare.

Physiognomy

The Polygonum aviculare-Chamomilla suaveolens community comprises open swards characterised in late spring and summer by mixtures of Polygonum aviculare, Chamomilla suaveolens, Capsella bursa-pastoris, Poa annua and young, scattered plants of Lolium perenne. Matricaria perforata and Chenopodium album are occasional to frequent but they do not dominate and typically other associates are relatively few in number and not abundant. Smaller herbs, such as Urtica urens, Veronica persica, Anagallis arvensis, Lamium purpureum, Plantago lanceolata and Medicago lupulina, or grasses like Elymus repens, Dactylis glomerata and Agrostis stolonifera are commonest among these companions with just very occasional taller herbs such as Rumex obtusifolius, R. crispus and Artemisia vulgaris. Bryophytes are absent or very sparse.

Sub-communities

Sisymbrium officinale-Polygonum arenastrum sub-community. Polygonum arenastrum is a frequent preferential here, forming denser prostrate mats among the more branched and somewhat ascending P. aviculare, and Bilderdykia convolvulus also occurs occasionally, its long flexuous stems trailing over the ground and other low herbs. Sisymbrium officinale is common, too, with Sinapis arvensis, Stellaria media and Senecio vulgaris occasional.

Plantago major sub-community. Scattered plants of Plantago major and, more occasionally, Coronopus squamatus are characteristic here, their rosettes often flattened by trampling.

Habitat

The Polygonum-Chamomilla community is an ephemeral vegetation type of disturbed and moderately trampled loamy and sandy soils throughout the lowlands of Britain.