Vicia hirsuta (L.) Gray (Ervum hirsutum)
Hairy tare is a scrambling annual, native in grassy places and rough ground throughout lowland Britain and is a weed of cultivated land. It is found in the hedgerows as well as in the open field. It occurs sporadically as a birdseed alien.
In a survey of arable weeds in 1971-73, hairy tare was absent to rare in some areas but common to abundant in others. It was found in 15% of the surveyed fields. Hairy tare is a problem weed in Central and Northern Europe.
There is evidence that hairy tare was a weed of crops in the Iron Age.
Hairy tare flowers from May to August. The pods are usually 2-seeded. Seed numbers per plant range from 200 to 250. Seed collected 15, 20, 25 and 30 days after flowering gave germination levels of 10, 64, 85 and 90% respectively when tested after a period of storage.
The seeds are relatively indifferent to light but there is slightly lower germination under a leaf canopy than in diffuse light. Scarification of the seed coat increases the level of germination.
Seed sown in the field and cultivated periodically, emerged mainly from October to May with just odd seedlings emerging through the summer. Seedling emergence was high for 3 years then decreased but some viable seeds still remained after 5 years.
Hairy tare seed mixed at different depths in soil, emerged from depths of 150 mm in both cultivated and undisturbed soil. In a sandy-loam soil, field seedlings emerged from the upper 0-90 mm with most seedlings coming from top 50 mm layer of soil. In a clay-loam soil, the hairy tare seedlings emerged from the upper 100 mm but again the majority were from the surface 0-50 mm.
Hairy tare seeds mixed with soil and left undisturbed had declined by 84% after 6 years but in cultivated soil the decline was 91%. After 5 years burial in soil, hairy tare seeds still retained 50% viability. Seed that had been dry stored for the same period had over 90% viability.
Hairy tare was a contaminant of cereal seed particularly home saved seed. It was also an impurity in crimson clover seed.
The seed has been found in cattle droppings.
Hairy tare seedlings are controlled by harrowing at the cotyledon stage, hoeing at the 3-leaf stage and by cultivator at the young plant stage.
In winter cereals in Germany, thermal weeding at early crop and weed stages reduced hairy tare but not after tillering of the cereal. Application of kainite, a natural mineral, was also effective at early weed stages but was weather dependant and like flame weeding caused some crop injury. Regular tine harrowing improved the level of control.
Hairy tare scrambles up cereal shoots and choosing a taller cultivar is unlikely to help but increased crop competition can reduce seed production by the weed.
Updated October 2007.