Volunteer cereals arise from seed shed at or before crop harvest. In barley the whole ear may break off while in wheat individual grains tend to fall from the spikelet. Some cultivars are more resistant to shedding and lose 5% of grains compared with an average of 16%. Cereal seedlings can emerge from straw used as mulch or as animal bedding. Seed can also be carried on and dispersed by farm machinery. Seedlings that reach maturity will produce a further generation of potential volunteer seedlings.