Ilex is a genus belonging to the family Aquifoliaceae, native of Afro-Eurasia, Australia and the Americas, established by Carl Linnaeus. It has over 300 species in the subtropical regions of both hemispheres. The genus includes species of trees, shrubs, and climbers, with evergreen or deciduous foliage and inconspicuous flowers. The genus was more extended in the tertiary and many species have adapted to laurel forest habitat. Ilex is adapted from sea level to more than 2,000 metres (6,600 ft) with high mountain species. Ilex are dioecious and have smooth, glabrous, or pubescent branchlets. The plants are generally slow-growing but over time can reach more than 10 m (33 ft). The genus name aquifolium is derived from the Latin (acer = "acute" & folium = "leaf"). Many are evergreen tree with some species growing to 25 m (82 ft) tall. Type species is the Mediterranean Ilex aquifolium described by Linnaeus.
Plants in this genus have simple, alternate glossy leaves, typically with a spiny toothed, or serrated leaf margin.
Ilex genus members also have small flowers. The flower is from greenish to white, with four petals. Male and female commonly flower on different plants, although there are exceptions. The pollination is done by bees and other insects.
The small fruits of Ilex, although often referred to as berries, are technically drupes. They range in color from red to brown to black, and rarely green or yellow. The "bones" contain up to ten seeds each. Some species produce fruits parthenogenetically, such as the cultivar 'Nellie R. Stevens'. The fruits ripen in winter and offer a pleasant color contrast with that of the plants' foliage. They are generally slightly toxic and can cause vomiting and diarrhea when ingested by humans. However, they are a very important food source for birds and other wildlife, and in winter the Ilex is an important source of food and shelter