The genus Ilex contains about 600 species of holly bushes and trees. They can be as small as 6 inches in height or as tall as 70 feet. The leaves can be spined or spineless, and the berries can be yellow, black or orange as well as red. Some species are deciduous, while others are evergreen. Holly species can be found in North and South America as well as Africa, Europe and Asia. China alone has over 200 native species. The largest number of species is found in subtropical areas of Asia and the Americas.
Hollies are usually grown as ornamental plants. Large hollies can provide a focal point for a garden. Smaller hollies can be grouped as foundation plantings. They make good hedges and privacy screens. Evergreen species, especially those with brightly colored berries, provide winter interest in the garden. Holly bushes are also a good choice for gardens intended to attract wildlife. They give shelter and protection from predators to many birds. Their berries provide food for both birds and wild animals. They are such a good food source that hollies were cultivated to feed cattle and sheep in medieval Europe.
Holly bushes are dioecious plants. Each individual plant has either female or male flowers, but never both. If female plants are to produce berries, they should be planted within 30 feet of a male plant. Most hollies grow best in full sun, although some species do grow in shade. All the evergreen species produce more berries when they are grown in the sun. Most holly bushes prefer a slightly acidic soil. They like good drainage and a soil that has lots of organic matter. Match the cold hardiness of the holly species to the location of the garden. Some species cannot tolerate very cold winters, while others will thrive in such conditions. Unless they are planted as a hedge, pruning is not necessary for hollies. However, they respond well to pruning, and can even be used for topiary.
Blue hollies (Ilex x meserveae) are widely grown as garden plants. This is a hybrid that has glossy, spiny leaves and red fruit. It has a high degree of cold hardiness and responds well to pruning. You can find blue hollies in most garden centers. They are usually sold under trademarked names like Blue Princess. Japanese hollies (Ilex crenata) are also widely available. This fast-growing shrub has tiny dark green leaves. It responds very well to pruning, so it is a common choice for foundation plantings. Convexa and Green Lustre are popular cultivars.
Holly berries are a great food for birds, but they will cause vomiting and diarrhea if they are eaten by people.