Plant of the Month: January

Ilex x koehneana 'Chestnut Leaf' AGM Common name: Holly Family: Aquifoliaceae Vital statistics Height and spread: 12m (40ft) x 5m (15ft) Form: Evergreen shrub or tree Soil: Moist but well drained, moderately fertile, humus-rich. Aspect: Full sun (best for variegated hollies) or partial shade. Hardiness: Fully hardy to frost tender.

Ilex x koehneana 'Chestnut Leaf' @ Rosemoor

There are two plantings of this striking subject at Rosemoor, one - a single plant - situated adjacent to Rosemoor House on the Old Nursery site. The second is a larger group, and this can be found in the Formal Garden's lower shrubbery, close to the Winter Garden.

Ilex

This genus contains 400 or more species of evergreen and deciduous trees, shrubs and climbers from woodland in tropical, subtropical and temperate regions, excluding western North America and southern Australasia.

Hollies are grown for their foliage and berries. In the garden, Ilex is best known as evergreen trees or shrubs, especially I. aquifolium and its numerous forms and hybrids.

The name Ilex comes from the Latin name for the holm oak (Quercus ilex).

Hollies have angular young shoots and leaves that are usually simple, alternate and stalked with margins that are entire, spiny or spine-toothed.

The insignificant flowers are small, often dull-white, produced in the leaf-axils with the males and females usually on separate plants.

The fruit, commonly called a berry (pulpy fruit containing one or more seeds) is really a drupe (the seed protected by a hard casing, the stone, contained in a fleshy layer within an outer skin). It is usually red or black but occasionally white, orange or yellow, with a thin, fleshy outer layer surrounding the seeds.

Failure to fruit by female plants is likely to be caused by the absence of a male plant growing nearby.

Hollies make good specimen trees, hedges and windbreaks. They are attractive additions to a woodland garden, and offer food and shelter to birds and insects.

Celtic druids thought that holly symbolised the sun and sprays of it were taken into dwellings during winter months. It was used by Romans during Saturnalia for decoration, as it is today at Christmas. North American Indian tribes used the emetic leaves of Carolina tea holly (I. vomitoria) for their Black Drink ceremony and holly branches were once used by chimney sweeps.

I. x koehneana (I. aquifolium x I. latifolia)

Bernhard Koehne, a German botanist and dendrologist first reported this hybrid in Florence in the late nineteenth century. The name was officially published in 1919. It is a cross between the English holly I. aquifolium and the Japanese holly I. latifolia.

Aquifolium is the classical name for holly and latifolia means broad-leaved.

It is a narrowly conical, evergreen, large shrub with olive green twigs and purple-flushed young shoots.

The leaves are large, 8-12cm (3-5in) long, mid-green, glossy and oblong to elliptic with large marginal spines.

Female plants bear red fruits 8mm (0.4in) across.

I. x koehneana 'Chestnut Leaf' is a robust clone, probably of French origin, female, with light or yellowish green leaves and shiny, pillar-box red berries. I. x koehneana and its cultivars can be used either as a specimen or planted in a group or avenue or screen.

In the USA there are many cultivars not available from commercial sources in the UK. The males include 'Jade', 'Ajax' and 'Chieftan' and some of the females are 'Agena', 'Ruby' and 'Wirt L. Winn'.

Related hollies

I. latifolia is originally from China and Japan. It is a narrowly conical, evergreen with olive-green twigs and oblong or oblong-ovate, entire or spine-toothed, glossy, leathery, dark-green leaves 8-18cm (3-7in) long. The flowers are yellowish green and the fruits are abundant and orange-red.

I. aquifolium (common holly or English holly) is a very useful evergreen tree or bush for the British climate. It can be used in industrial and coastal areas and for hedges, as well as in woodlands and as specimen trees.

The typical form is pyramidal or oblong with grey bark. Its leaves are elliptic or ovate, glossy, dark-green, 5-10cm (2-4in) long with entire, spiny, spine-toothed or wavy margins and long lasting red, or rarely orange or yellow berries, 4-6mm (0.1-0.25in) across.

Its many cultivars include I. aquifolium 'Argentea Marginata', I. aquifolium 'Golden Milkboy' and I. x aquifolium 'Pyramidalis Fructu Luteo', all of which have an Award of Garden Merit.

AGM

The RHS Floral B Committee awarded Ilex x koehneana 'Chestnut Leaf' an Award of Garden Merit and described it as: Small evergreen tree of conical habit. Leaves elliptic, to 15cm long, yellowish-green and regularly spined. Flowers small, dull white; berries large, red.

Cultivation

Grow in moist, but well-drained, moderately fertile, humus-rich soil in full sun (for best variegated colour) or partial shade.

Plant or transplant in late winter or early spring.

Prune, to remove crossing shoots and maintain a healthy framework, in late winter or early spring.

Prune free standing specimens only in the early years; clip formally grown plants in summer and hedges in spring.

Propagation

Sow seed in containers in a cold frame in autumn. Germination may take 2 - 3 years and cultivars will not come true from seed.

Take semi-ripe cuttings in late summer or early autumn.

Pests and Diseases

Scale insects and leaf miners may be a problem, as may aphids on young shoots.

Occasionally, hollies may suffer from root rot Phytophthora.