Anthemis arvensis L.
Corn chamomile is a native annual, locally common on light arable land and waste places throughout the UK. It can sometimes act as a biennial. A long established weed of arable land on dry calcareous or sandy soils, it is found in cereals and occasionally on dry grassland. It has a scattered distribution and is locally common in southern England, the central Midlands and East Anglia. It prefers dryer areas with low summer humidity and is relatively tolerant of dry conditions. In early surveys of Bedfordshire, Hertfordshire and Norfolk it was especially associated with temporary grass or clover seed crops having been introduced as a contaminant with the crop seed.
An aromatic plant with a faintly scented foliage, corn chamomile is the least common of the annual mayweeds. Corn chamomile is phenotypically plastic and is very variable in size and habit. Hybrids may occur with scentless mayweed (Tripleurospermum inodorum) but these are sterile.
Flowering begins in late-May or early-June, reaching a peak in July and continuing through into August. Corn chamomile is able to grow new shoots when cut down during cereal harvesting and may flower again in stubble in September. The ray florets are female, the disc florets are hermaphrodite but plants are self-incompatible and cross-pollination is via a range of pollinating insects. The average number of seeds per flowerhead is 65-90. An average plant may produce 2,100-4,200 seeds.
Seed germination takes place mainly in the autumn from September to October and in spring, but odd seedlings emerge throughout the year. Germination levels are increased if the seedcoat is removed. The period from germination to fruiting is around 100 days. Corn chamomile is frost-hardy and can grow as a winter annual. Overwintered plants come into growth in March, internode elongation of the flowering stems begins in late-April to early-May.
Seeds stored in soil for 11 years retained 47% viability.
Seed has been found in cattle and bird droppings. Passage through the digestive system of some birds is said to improve seed germination. Corn chamomile seed has been a frequent contaminant in clover and grass seed.
The chief method of control is to prevent the weed seeding through surface cultivations in spring and summer, and by the inclusion of root crops in the rotation. Plants should be hoed-off or hand-pulled if necessary. On poor land deficient in lime the traditional practice was to add lime to discourage the corn chamomile.
The larvae of Apion sorbi (Coleoptera) and Homoeosoma saxicola (Lepidoptera) have been recorded on corn chamomile flower heads eating the receptacle.
Updated October 2007.