Evergreen oak

Appearance

An evergreen tree of large size, attaining in favourable places a height of 21–28 m, and developing in open situations a huge head of densely leafy branches as much across, the terminal portions of the branches usually pendulous in old trees. The trunk is sometimes over 6 m in girth. The young shoots are clothed with a close grey felt. The leaves are very variable in shape, most frequently narrowly oval or ovate-lanceolate, 4–8 cm long, 1.2–2.5 cm wide, rounded or broadly tapered at the base, pointed, the margins sometimes entire, sometimes more or less remotely toothed. When quite young, both surfaces are clothed with whitish down, which soon falls away entirely from the upper surface leaving it a dark glossy green; on the lower surface it turns grey or tawny, and persists until the fall of the leaf; the petiole is 3–16 mm long. Fruits are produced one to three together on a short downy stalk, ripening the first season; the acorns usually 12–18 mm long in the UK, the cups with appressed, downy scales.

Naming

The resemblance of the foliage to that of the common European holly, "Ilex aquifolium", has led to its common and botanic names. The name ' was originally the classical Latin name for the holm oak, but later adopted as a botanical genus name for the hollies.There are two subspecies:
⤷ "Quercus ilex" subsp. "ilex". Native in the north and east of the species' range, from northern Iberia and France east to Greece. Leaves narrow; acorns 2 cm long, bitter tasting.
⤷ "Quercus ilex" subsp. "rotundifolia". Native in the southwest of the species' range, in central and southern Iberia and northwest Africa. Leaves broader; acorns 2.5 cm long, sweet tasting.

Habitat

Holm oak grows in pure stands or mixed forest in the Mediterranean and often at low or moderate elevations, such as coastal California. One of the plant associations in which holm oak is found is the holm oak/Atlas cedar forests of the Atlas Mountains. In Morocco, some of these mixed forests are habitat to the endangered primate, Barbary macaque, "Macaca sylvanus".

Holm oak is prevalent from Portugal to Italy along the northern Mediterranean coastal belt, and from Morocco to Tunisia along the southern Mediterranean coast.

Holm oak is damaging biodiversity in the United Kingdom and is listed as an alien invader. Normally the tree is unable to withstand severe frost, which would prevent it from spreading north, but with climate change, it has successfully penetrated these areas. The largest population of Holm oak in Northern Europe is present on and around St. Boniface Down on the Isle of Wight and into the neighbouring town of Ventnor, and has shown to tolerate the high winds on the downs. It is thought that this population's propagation has been bolstered by native Eurasian jays, which harvest acorns from oak trees and store them by burying them in the ground where they may then germinate.

Uses

The wood is hard and tough, and has been used since ancient times for general construction purposes as pillars, tools, wagons, vessels and wine casks. It is also used as firewood and in charcoal manufacture.

The holm oak is one of the top three trees used in the establishment of truffle orchards, or truffières. Truffles grow in an ectomycorrhizal association with the tree's roots.

The acorns, like those of the cork oak, are edible and are an important food for free-range pigs reared for ibérico ham production. Boiled in water, the acorns can also be used as a medicinal treatment for wound disinfections.

"Q. ilex" can be clipped to form a tall hedge, and it is suitable for coastal windbreaks, in any well drained soil. It forms a picturesque rounded head, with pendulous low-hanging branches. Its size and solid evergreen character gives it an imposing architectural presence that makes it valuable in many urban and garden settings. While holm oak can be grown in much of maritime northwestern Europe, it is not tolerant of cold continental winters.