It is an evergreen shrub or small tree up to 15 m tall, with dense, sclerophyllous foliage. The leaves are 1.6-12 cm long with a 4–25 mm petiole and spiny margins, somewhat resembling those of the holly, hence its English name; they are dark green when mature and generally shiny on top, and have a smell resembling almonds when crushed. The flowers are small (1-5 mm), white, produced on racemes in the spring. The fruit is a cherry 12–25 mm diameter, edible and sweet, but contains little flesh surrounding the smooth seed.
There are two subspecies:
It is a persistent member of chaparral communities, being slow-growing but long-lived. In the absence of fire, P. ilicifolia will outlive or outshade surrounding vegetation, making room for seedlings. Eventually, it will form extensive stands co-dominated by scrub oak. Although it will stump-sprout after fires, the seeds are not fire-adapted like those of many other chaparral plants are. Instead, it relies on the natural death of surrounding vegetation during long periods of fire-free conditions to make room for its seedlings.
The seeds will only germinate after an acid treatment, such as that received when they pass through the digestive tract of coyotes or birds which feeds on the fruits. The coyotes are discouraged from eating the seeds themselves by cyanide, which is released from the seeds if they are cracked. Others report that germination levels are high with only suitable moisture and temperature levels. Sufficient light levels are also reported to be necessary for germination.
The caterpillars of the pale swallowtail (Papilio eurymedon) feed on this and other members of the riparian woodland plant community.