A very large genus of deciduous and evergreen trees and shrubs found in almost all parts of the habitable globe except western N. America and Australasia. In gardens they are best known by the evergreen group, especially by I. aquifolium and its numerous forms and hybrids. They have very frequently angular young shoots; leaves alternate, stalked. Flowers of little or no beauty, small, often dull white, produced in the leaf-axils, the males and females usually on separate plants. Petals and stamens four to six. Fruit although commonly called a berry, really a drupe, usually red or black, with a thin, fleshy outer layer, surrounding one of several nutlets – generally termed seeds.
The most valuable hollies are undoubtedly those with evergreen foliage, but the deciduous ones, especially those earlier known under the generic name of Prinos, are sometimes handsome in fruit. Owing to the frequently unisexual character of the plants, these often fail to appear if both sexes are not grown. All the species like a moist, loamy soil. (For propagation, see under I. aquifolium.)
The standard work on Ilex is: T. Loesener, ‘Monographia Aquifoliacearum’, Nov. Act. Acad. Caes. Leop.-Carol. Nat. Cur., Vol. 78 (1901), pp. 8-500, and Vol. 89(1908), pp. 20-312. For the species of China, this is superseded by: S.-Y. Hu, ‘The Genus Ilex in China’, Journ. Arn. Arb., Vol. 30 (1949), pp. 283-344 and pp. 348-387, and Vol. 31 (1950), pp. 39-80, 214-40 and 242-63.