Quercus petraea - Sessile Oak

The Quercus petraea, also known as the Sessile Oak, closely resembles its cousin the Quercus robur. Observing the way the acorns are attached to the branches is a good technique to differentiate them: the former bears acorns directly attached to their support, while the fruits of the latter are suspended from peduncles. These two majestic trees are very often found in forests. This noble species, a symbol of longevity, has a wide and irregular crown, massive and twisted branches located towards the base of the trunk, beautiful deciduous foliage that provides pleasant shade in summer, and numerous acorns that delight small animals. Large and tall, it grows more slowly than Quercus robur but can reach a venerable age. Its large development requires space, in a large garden.

The Sessile Oak belongs to the Fagaceae family. It is native to a large part of temperate Europe. It thrives in sub-oceanic to oceanic climates, or mild continental climates which are not too dry. It is a species of hills and low mountains, where it can be found up to 1600m (5249ft) in altitude. It prefers sandy-loamy soils that are neutral to slightly acidic, cool, deep, and well-drained, although it can tolerate slightly rocky, lightly chalky, and sporadically dry soils.

In its natural environment, it can reach a height of 40m (131ft) with a spread of 25 to 30m (82 to 98ft), while its trunk can measure up to 2m (6ft 7in) in diameter. In our gardens, it will reach an average height of 27m (88ft 7in) with a spread of 20m (65ft 7in). This oak can live up to 1000 years according to some estimates. Deciduous oaks have the advantage of producing good and abundant soil which is favourable to the growth of plants that germinate under their cover.

The growth of this oak is rather slow. Its habit is massive, slightly wider than it is tall. The relatively short trunk is covered with initially green and smooth bark, which later becomes dark, thick, and slightly fissured. The crown is irregular in shape, rounded oval and open. Its young branches are grey-brown and shiny. The late deciduous foliage consists of long petiolate, alternate, soft, obovate leaves that can reach 5 to 15cm (2 to 5.9in) in length and 3 to 8cm (1.2 to 3.1in) in width. Each leaf is divided into 9 to 12 slightly marked and irregular, rounded lobes of a medium green, matte on the upper side, with the lower side being paler. The leaves turn brown relatively late in autumn, and remain attached to the branches for a while before falling. The flowering of this oak occurs in April-May, shortly after the appearance of the foliage, on this year's shoots. The female flowers are placed in a cup directly attached to the branch: this distinctive feature is the origin of the species name, sessile. The male inflorescences are elongated, pendant catkins, tinged with yellow. They are produced at the base of shoots. The female flowers, at the axils of the leaves, give way to ovoid and elongated acorns, measuring 1.5 to 3cm (0.6 to 1.2in) in length. They are often grouped in pairs or threes, directly on the branches. A cup covered with scales covers one-third of the acorn. The colour changes from green to brown at maturity, in September and October. The root system of this tree is deep and powerful, with both a taproot and extensive lateral roots, providing a solid and long-lasting anchorage in deep and sandy soils.

The Sessile Oak is a tree that should be protected and preserved if it grows in a park or a large garden, if only for the symbolism surrounding an old subject, a true cornerstone of an ancient garden. It can be planted either in isolation or in rows in a very large garden. It also provides pleasant shade in summer. Its acorns feed small animals such as squirrels and jays. It can be associated, with maples, plane trees, lindens, and sophora in a large park. The root system of oaks, which tends to be deep, allows for the other plants at their base: consider, for example, bear's breeches, Anemone blanda, Omphalodes verna, periwinkles, Naples cyclamen, dead-nettles, shade-loving perennial geraniums, Ophiopogon, Liriope muscari...