barley grass, mouse barley, squirrel
Hordeum murinum L.
Wall barley is an annual grass common in central, southern and eastern England, and scattered elsewhere. It is found on waste and rough ground and barish patches in rough grassland. It occurs on the margins of cultivated fields. Distribution is related both to the availability of ruderal habitats and to climate. Frequency decreases with increasing rainfall combined with decreasing temperatures, although, it can cope with greater rainfall if temperatures are higher. In ruderal situations it extends further into cooler wetter regions by taking advantage of features such as the base walls where conditions are locally warmer and drier.
Wall barley is part of a complex of overlapping subspecies whose centre of distribution is in the Mediterranean region. Subspecies murinum is the native grass in the UK. Sub-species leporinum and glaucum are introduced casuals. In Australia, biotypes of the latter two sub-species have been reported with resistance to the herbicide paraquat
In New Zealand, wall barley is a particular problem to stock. The sharply pointed seeds can penetrate the eyes, mouth and skin of sheep causing animal losses and devaluing the pelts. The level of damage is influenced by the breed of sheep, mainly due to differences in the structure of the coat. Sheep dogs too are affected when the seeds become embedded between their toes.
Wall barley flowers from June to July.
Wall barley seeds tend to germinate under cool moist conditions in the autumn after shedding. The seeds germinate under high or low light intensity and in darkness. In glasshouse conditions, seed sown on the soil surface, at 2 mm or 25 mm deep emerged well. With seed sown at 50, 75 or 100 mm deep, emergence gradually declined with depth. The deeper sown seeds germinated but failed to emerge.
Seed shed in cultivated soil rarely persists for more than 2 years. A small proportion of seeds may possess innate dormancy but it is thought unlikely that wall barley will build up a large seedbank in the soil.
In pasture, the grass should be cut or kept closely grazed down to prevent seeding and reduce injury to stock from the seed awns. Once the weed has flowered and set seed, even goats will not eat the seed heads. Maintaining a short but not overgrazed sward has eradicated wall barley within 2 years. Wall barley does not compete well against a mixture of perennial ryegrass and white clover in the sward.
Updated October 2007.