Quercus dentata 'SIR HAROLD HILLIER'

Oak trees are an integral part of our landscape, whether they come from America, Asia, or southern Europe. They border our ponds, adorn mixed forests, and many species and cultivars are popular in large parks and botanical gardens. Daimyo oak originates from Asia, specifically from Mongolia. It extends south and east through central and southern parts of Asia, reaching as far as Korea and Japan. It was introduced to Europe in 1830. It is a large tree with sparse branching, where its beauty is ensured by its huge leaves, which are used in Japanese cuisine to wrap kashiva mochi (a Japanese dessert) but are not eaten. It is an ideal tree for a continental climate, where it benefits from seasonal changes and a cooler winter, which allows it to grow somewhat slower than in warm maritime climate, but it branches better.

Sir Harold Hillier (1905-1985) was a renowned British horticulturist and dendrologist who became famous for his work in horticulture and plant conservation. In 1953, he founded the Hillier Arboretum, now known as the Sir Harold Hillier Gardens. Located in Ampfield, near Romsey in Hampshire, it covers an area of 180 acres. It contains over 42,000 trees and shrubs, including rare and endangered species. Sir Harold Hillier was knighted in 1983 for his contributions to horticulture. His gardens are now managed as a charitable organization and serve for conservation, education, and recreation.

The origin of the Sir Harold Hillier variety of Daimyo oak is somewhat mysterious, as it shares many characteristics with the Carl Ferris Miller variety, to the point of being almost identical. It has been proven that the seeds of both varieties came from Korea. The leaves of this tree are among the largest of all oaks, as they can reach up to 30 cm in length and half that width on a mature tree. They are conspicuously toothed with rounded lobes, glossy, minute down, and very stiff, which is more common for evergreen plants. They look almost exotic, and their shape invites sharp contrast with plants that have differently shaped or textured leaves. Their colour from spring to late summer is pleasantly medium green, and in autumn they enchant us with colourful transformations in rich shades of yellow, red, and orange, creating quickly changing maps, and before they dry, they turn a peculiar salmon-orange, which looks very attractive on such large leaf surfaces. Although a deciduous tree, its dry leaves often remain on the branches until the end of winter and fall off only with the opening of new leaf buds. On windy days, their rustling is noticeable, pleasant, and quite loud, like a bamboo wind chime.

This oak grows moderately fast and is considered a smaller tree compared to common oaks. Its final height in C.E. climate in gardens with limited root space can reach around 6-8 meters with half the width, but in parks and open landscape, it can grow up to twice that, though over many decades. Young trees make upright branches and form a narrowly pyramidal canopy, which becomes slightly rounded with age. They are often pruned in late winter to achieve a denser habit and maintain a smaller size. Shaped trees look luxurious and offer slightly larger leaves. The trunk is heavily furrowed.

It is not difficult to grow, just avoid waterlogged or water-retentive soil, where a new plant could rot from the roots. Fertilization is not required, nor is it recommended in order to ensure good maturation of new shoots and better branching. Soil pH does not matter. Plant it in full sun only. Newly transplanted trees need a strong support for 2-3 years until they establish. It is very hardy and has already survived winters in Canada at -37 °C.

Last update 21-02-2025