Ilex crenata 'Caroline Upright' DARK STAR Japanese holly, box-leaved holly
Ilex
The genus Ilex, commonly known as holly, is very extensive and includes more than 400 species of evergreen and deciduous shrubs and trees, distributed from the tropics of South America through the subtropics of Asia to the temperate zones of Europe. In addition to the possibility of variegated foliage, their greatest advantage is evergreen character, at least in most species, which makes them an excellent complement to deciduous trees and shrubs during the dormant season. Moreover, many hollies naturally lack spines, which will please those who dislike prickly shrubs. The most horticulturally significant are the East Asian species, among which the Japanese holly (Ilex crenata) stands out. This species was described in 1784 by the Swedish botanist Carl Peter Thunberg (1743–1828) during his stay in Japan.
Japanese hollies are very useful and elegant evergreen shrubs that many people at first glance mistake for boxwoods or honeysuckles because of their small, glossy leaves. This very resemblance has predestined them to become the ideal replacement for true boxwoods, which in Europe are gradually disappearing under the pressure of the massive invasion of the box tree moth and due to the fungal disease known as box blight, which has been devastating plantings especially in the British Isles. Japanese hollies, however, are thornless, offer a wide range of shapes and sizes, and require only minimal care. Since they are naturally quite variable, new mutations and cultivars often appear, each slightly different from the last – and every novelty is, of course, a welcome delight.
Caroline Upright or DARK STAR is a selection of Japanese holly with upright growth and deep green leaves. They are broadly elliptic. In mid spring opens a profusion of small, creamy white flowers serving plenty of bee food. It is a female variety so if pollinated by a male plant from nearby they are followed by small, black berries in autumn. They are not edible nor poisonous for people but contain saponins which cause severe discomfort if eaten in quantity. They are important bird food in winter. Stems are pale grey-green.
It grows about 20-30 cm per year and naturally forms dense, upright growing, many-branched shrubs. You can use it like a box plant - in the same spot or a container or among other large-leaved, evergreen plants to which its delicate foliage will provide a great contrast. As every other Japanese holly it is ideal for bonsai making as well as for hedging. It can be pruned and clipped in almost any way from early spring by end July.
Japanese holly is tolerant of most soil types except heavy clay, but it thrives best in well‑drained, evenly moist, acidic soil, occasionally enriched with slow‑release fertilizer. It has a strong root system that copes better with poorer conditions than English hollies and adapts easily to the limited root space of containers without showing signs of stress or drought. It is hardy to about −27 °C (USDA zone 5) and is also suitable for outdoor planters with good drainage and where it requires more frequent but careful watering, including during frost‑free winter days.
Last update: 09-09-2022
