"Banksia ilicifolia" has a stout trunk up to in diameter, and rough, fibrous, grey bark which is up to thick. New growth takes place mainly in summer. Young branchlets are covered in hair which they lose after two or three years. Leaves grow on stems less than two years of age, and are arranged in a scattered pattern along the stems although crowded at the apices (branchlet tips). Resembling those of holly, its leaves are a dark shiny green colour, and variously (egg-shaped), elliptic, or (wavy) in shape, and long. Generally serrated, the leaf edges have up to 14 prickly "teeth" separated by broad v- to u-shaped sinuses along each side, although some leaves have margins lacking teeth. The leaves sit atop petioles in length. The upper and undersurface of the leaves are initially covered in fine hairs but become smooth with maturity. Flowering takes place from late winter to early summer. The inflorescences are dome-shaped flower heads rather than spikes as many other banksias, and arise from stems that are around a year old. No lateral branchlets grow outwards from the node where the flower head arises. The flower heads measure in diameter, and bear 60 to 100 individual flowers. The inflorescences pass through three colour phases, being initially yellow, then pink, then finally red, before falling away from the head. One to three follicles develop from fertilised flowers, and remain embedded in the woody base of the flower head. Each follicle bears one or two seeds.