The most abundant bright red berries of autumn are those of firethorn, Pyracantha coccinea. They resemble English hawthorn, cotoneaster and toyon berries, but are shinier and more abundant. Their weight causes their limbs to sag. Most are either rich deep red, or brighter slightly orangy red. Orange berries are uncommon locally. Cultivars with yellow berries are less vigorous and rare.
Berry production may seem to be more variable than it actually is. Healthy plants typically produce a profusion of berries. They only seem to be more profuse if they ripen late, after migratory birds fly south. Such birds are voracious with early berries. Overwintering birds are less numerous, and consume berries slower. Regardless, few berries last long enough to deteriorate and get messy.
Firethorn is thorny enough to function as an impenetrable hedge. However, it is unpleasant to prune with all those thorns. Also, pruning without removing the stems that bloom and produce berries takes effort. Upright cultivars can get higher than downstairs eaves. Some cultivars get only a few feet tall as they sprawl over the ground. Even without berries, the evergreen foliage is appealing.