Common holly

Botanical data

Family

Aquifoliaceae (Aquifoliaceae)

Height

2–6 m

Width

1.5–4 m

Habit

Conical

Growth rate

Slow

Position

Full sun, Partial shade, Shade

Soil

Humus-rich, Loamy, Sandy

pH reaction

pH 5.5–7.5

Moisture

Moderate, Moist

Bloom

May–June

Hardiness

USDA 7a–9a

Propagation

From cuttings, From seed

Characteristics

A densely branched shrub or small tree with a conical outline that broadens and spreads with age. In cultivation it usually stays a shrub 2–4 m tall, while old specimens in fertile, sheltered positions reach about 6 m; in the mild, oceanic climate of Western Europe it grows into a small tree about 10 m tall, exceptionally taller. It grows slowly — reaching its final size takes several decades, but in return it lives more than a hundred years. The bark stays smooth and grey-green for a long time. The leaves are evergreen, leathery, stiff, dark green and strongly glossy above, paler beneath, with a margin that is wavy and tipped with hard spines. A single leaf persists on the shoot for several years, so the shrub renews its foliage gradually and never stands bare. The spininess is not uniform across the whole plant: leaves in the lower part of the shrub, within reach of grazing animals, tend to be markedly more bristly than those higher in the crown, which often have an almost smooth margin. The flowers are small, white, four-petalled, clustered in the leaf axils; they open in May and June, are subtly fragrant and are readily visited by bees. Dioecy is visible on inspecting a flower: a male specimen has four prominent stamens and a vestigial pistil, while a female one has a green, spherical ovary in the centre and reduced stamens. Without pollen carried from a male plant, a female specimen will not set a single berry — this is the commonest cause of disappointment with a bought "holly that does not fruit." The second frequent cause is too deep a shade: shade tolerance concerns growth, not flowering, so beneath a dense tree canopy the shrub grows healthily but sets few flower buds and fruits sparingly. The fruits are spherical drupes about 1 cm in diameter, ripening blood-red from September and persisting on the branches through winter. For humans they are toxic, while for birds they are a reserve for the hungry gap: thrushes and fieldfares usually eat them only in late winter, once the frosted flesh has softened.

Popular cultivars

‘J.C. van Tol’

A female, self-fertile cultivar — it sets fruit even without a male specimen nearby, though it fruits more heavily with a pollinator. Leaves dark green, glossy, almost spineless, so safe beside paths and in small gardens. Berries large, bright red, abundantly set.

‘Pyramidalis’

A female, self-fertile cultivar with a dense, conical habit and leaves bearing few spines. Fruits heavily and regularly; good for narrow hedges and as a specimen with a distinct, upright silhouette.

‘Alaska’

Regarded as one of the hardiest cultivars of the species, which is decisive under Polish conditions; introduced into cultivation around 1960 in Germany. Female, with a narrow, erect habit and narrower, more strongly toothed leaves than the type. Fruits every year, and the berries persist into March.

‘Ferox Argentea’

A male cultivar — it will not set fruit and is planted as a pollinator for female specimens and for its foliage alone. The spines grow not only on the leaf margin but also on the upper surface of the blade, hence the English name hedgehog holly; the leaf margin is creamy white.

‘Silver Queen’

Despite the name suggesting a female sex, this is a male cultivar and does not fruit — planted as a pollinator and for its ornamental foliage. Young shoots purple, young leaves with a pinkish tinge, mature ones dark green with a broad, cream margin.

‘Handsworth New Silver’

A female, fruiting cultivar with dark purple shoots and narrow, spiny leaves with a broad cream margin. Forms a large, dense shrub; distinguished with the RHS Award of Garden Merit.

Growing and care

Companion plants

The evidence level indicates whether the relationship is backed by research, observation, or gardening tradition.

Diseases and pests

Toxicity

History and origin

The species name aquifolium was formed from the Latin words acus ("point, needle") and folium ("leaf") and refers to the spiny margin of the blade. A shrub that in the depths of winter stands green and laden with red berries has been treated since antiquity as a sign of the persistence of life: the Romans sent each other holly branches during the Saturnalia, and Christianity took the custom over into Christmas observance — it was fixed, among other things, by the English carol "The Holly and the Ivy." The German name Stechpalme, meaning "spiny palm," arose because in countries without palms it was holly branches that were blessed on Palm Sunday. Holly wood is hard, heavy and almost white, with a very fine grain; it was used for inlay work, tool handles, walking sticks and white chess pieces, and, dyed black, it substituted for ebony. Birdlime was boiled from the bark. The plant was introduced into gardens early and several hundred cultivars were selected, differing in habit, leaf colour, spininess and sex. The reverse side of this success is naturalisation: on the north-west coast of North America, common holly has escaped from cultivation into the forests and is regarded there as an invasive species, displacing the native understorey.

Uses

It is most often planted as an evergreen hedge: dense, impenetrable and spiny, so genuinely a barrier, and at the same time tolerant of clipping and able to regenerate from old wood — it is therefore also suitable for clipped forms and for a specimen with a striking silhouette. Thanks to its tolerance of deep shade it succeeds where most ornamental shrubs fail: beneath the canopy of old trees, against north-facing walls, in shaded corners of a plot. It is worth distinguishing two goals, however: if what matters is the evergreen mass and screening alone, deep shade is fine, but if it is the red berries, we plant the female specimen in partial shade or in a bright spot, because the darker it is, the sparser the flowering and the fewer the berries. Fruiting female specimens can be the only source of colour in the garden in December and January, and branches with berries are a classic material for wreaths and arrangements. Ecologically the shrub works on three levels: the flowers give bees nectar in May and June, the dense, spiny interior is a safe nesting place for small birds, and the berries provide late-winter food for thrushes. Because of the toxic berries and hard spines it is better not to plant it beside a sandpit, a dog run or along narrow paths.

Trivia

• The spininess of holly leaves varies within a single plant: blades within reach of animals' mouths are heavily bristled, while those higher up often have smooth margins. Research on this species indicates that it is an induced defensive response to browsing, not a fixed trait of the cultivar.
• The German name Stechpalme ("spiny palm") and the English tradition of festive wreaths describe the same cultural mechanism: in Northern Europe, evergreen, prickly branches substituted for unavailable palm fronds and symbolised life persisting despite winter.
• In Great Britain, holly is the spring larval host plant of the holly blue butterfly (Celastrina argiolus) — its spring generation lays eggs on holly, and its summer generation on ivy.
• The sex of a cultivar cannot be read from its name. The classic example is Silver Queen — despite the "queen" in its name, it is a male cultivar that will never set fruit.

Frequently asked questions