Family: Aquifoliaceae
Common Name: Holly

There are 400 species in this genus of mostly hardy, evergreen and deciduous trees which are found predominantly in temperate climates of the northern hemisphere. They are grown for their attractive, thick, dark green, leathery leaves and their cheerful berries which are produced mainly in winter. Some of the leaves have smooth margins, while others have distinctive, toothed, spiky edges. The small, insignificant, greenish white flowers are usually unisexual and the berry, though commonly red, can also be yellow or black. Although hollies will grow in warm areas, most need a cooler climate to do well and produce good crops of berries. Dollies make good hedges and windbreaks, and also pleasing specimen plants in lawns, shrub borders and woodland gardens.

Species

I. aquifolium, common or English holly, is popular in Europe and North America for the colour it provides in winter. It has been very widely hybridized. It is the holly we associate with Christmas. A very hardy, rather slow growing, evergreen tree, to about 25 m (80 ft), it forms a roughly pyramidal shape. The spiky, deep green leaves become smoother with age. As the flowers are unisexual, berries are only found on female trees when there is a male tree close by to provide pollen. Holly makes a beautiful specimen tree and can also be used as a hedge. It can tolerate very cold winters and, once established, can also tolerate drought. The wood from this species is used for veneers and inlays. Some cultivars bear only male flowers, others only female, so if a crop of berries is required, it is necessary to grow a mixture of varieties. 'Silver Queen' is the best of the silvery cream, variegated forms, bearing male flowers only. The leaves are margined with creamy white. A silvery variegated cultivar like 'Argentea Marginata', with female flowers, could be chosen to grow with it. Other popular cultivars include 'Golden Queen', which is actually a male holly, with spiny leaves boldly edged with gold. A very fine holly, it will pollinate female cultivars. It makes a superb specimen tree in a lawn. 'Ferox', known as hedgehog holly because the upper surfaces of the leaves are prickly, is a compact holly, with purple hark, which does not produce berries. 'Ferox Argentea' is a slow-growing, variegated form with silvery white markings; 'Ferox Aurea' is slow growing, to around 2 m (6 ft), with golden variegations; 'J. C. van 'Fol' is a self-fertile, female holly producing heavy crops of berries. The clusters of bright, glossy, red berries, which remain on the bush throughout winter, and the deep green foliage make this a handsome garden specimen.

I. cornuta, Chinese or horned holly, is a much-branched, evergreen shrub or small tree, which is self-fertile. It tolerates a warmer climate and produces larger berries than the common holly.

I. crenata, Japanese or box-leafed holly, is a compact, evergreen shrub, with stiff branches, small, narrow, deep green leaves and small, black berries. In Japan it is favored for bonsai, and it is also used as a hedge and for topiary. There is a wide range of cultivars of both I. cornuta and I. crenata. There are numerous dwarf forms of Ilex crenata including' Compacta','Helleri','Hetzii' and 'Morris Dwarf'. These would make good dense ground cover if mass planted in groups or drifts.

Cultivation

Propagate hollies from seed, cuttings or by grafting. Seed can take up to a year to germinate and the sex of the plants will not be known until they flower some years later. However, this is not important if growing large numbers for hedges or screens. Cuttings or grafting, using seedling understock, are used to reproduce varieties and cultivars. Cuttings, 5-8 cm (2-3 in) long, are taken in autumn from mature wood of the current season. Hollies will grow in most garden soils but need regular watering in summer when young. Prune in late winter to encourage dense growth.

Climate

Zone 6 for the species listed below.