Suppression by three grass species of broom seedling emergence and survival

Grass ground covers are often used in forestry to suppress weed germination, but little is known on how best to use grasses to suppress broom (Cytisus scoparius). In this field study, three grass species, Yorkshire fog (Holcus lanatus), Italian ryegrass (Lolium multiflorum) and perennial ryegrass (Lolium perenne), were sown at three rates in autumn and spring, then suppression of broom germination and survival of seedlings was measured. Scarified broom seeds sown at the same time as the grasses produced large numbers of competitive plants by the final assessment 12 months after sowing, regardless of the time of sowing, species of grass sown or rate of grass sown. However, no seedling emergence was recorded for the treatments in which broom seeds were sown 6 months after the grass ground cover had established. All three grass species established well, although only Yorkshire fog performed well in both seasons. Grass ground covers showed some potential to be used as part of weed management for broom in planted forests, but probably only if herbicides can also be used to control broom establishing at the same time as the grass.