Quercus ilicifolia Tromp Ball - Bear Oak

Quercus ilicifolia 'Tromp Ball' is a variety of holly-leaved oak characterised by a bushy and rounded habit. Grafted on a stem, it forms a unique small tree with a globular and irregular crown. This variety has ornamental deciduous foliage, reminiscent of holly leaves, but turns a beautiful red in autumn. Its size makes it suitable for gardens of all sizes. While not demanding, this oak prefers well-drained, slightly acidic soils that are not too dry.

Quercus ilicifolia 'Tromp Ball' (also known as Quercus ilicifolia 'Nana') was selected at the Trompenburg Arboretum in the Netherlands and described in 2001. It is derived from the holly-leaved oak (Quercus ilicifolia), a species native to the eastern United States, introduced to Europe in 1800. All oaks belong to the Fagaceae family.

'Tromp Ball' naturally forms a bush that can reach 2 to 4 metres in height and width. Its habit is rounded, irregular, but well-branched. Its shoots are grey-brown with silver buds. Its foliage is deciduous, developing in spring and falling in autumn. The leaves are generally rectangular, ovate, or obovate, measuring 5 to 10 cm long and 3 to 5 cm wide, with 5 to 7 small lobes. Each lobe ends in a thorn, which is the tip of a vein. The leaf blade is leathery, dark green and shiny on the upper side, grey-green or whitish-green on the underside. In autumn, the leaves turn red, a colouration that will be more pronounced in suitable climates and soils. This oak blooms in May, bearing male flowers in catkins and female flowers in clusters. This flowering, which attracts pollinators, has no decorative value. The fruits are oval acorns, pointed at the top, measuring between 1 and 1.6 cm in diameter and 1 cm long. Each acorn is inserted into a grey or olive-brown cup cup that covers nearly half of the fruit. The acorns mature in the second year after flowering.

When grafted on a stem, Quercus ilicifolia 'Tromp Ball' can be planted as a specimen tree on a lawn or in the centre of a bed of ground cover perennials, for example. It can also be planted alongside low-growing shrubs chosen for their flowering or autumn colours. It will pair well with dwarf barberries or dwarf conifers, for instance. In any case, it deserves to be closely observed.