Roman hazelnut (Römische Zellernuss)

Roman hazelnut, also known as Römische Zellernuss, is a very old, traditional, and globally valued hazelnut variety originating from Italy. Due to its outstanding, regular, and abundant productivity, high resistance of the catkins and wood to frost, and large nut size, it is one of the most widespread and sought-after companion varieties and pollinators in modern commercial orchards throughout Europe and the Balkans.

It is a fully cross-pollinated variety with pronounced protandry. It cannot set fruit with its own pollen, so the presence of compatible pollinator varieties in the orchard is essential. Since it flowers medium-late to late, it requires partners with the same flowering period. It is distinctly incompatible with the Cosford variety, as they share the same sterility alleles and cannot pollinate each other. The best, biologically synchronized, and field-proven pollinators for Roman hazelnut are Hall’s Giant, Istrian Round, and Nocchione. Roman hazelnut itself produces large quantities of viable pollen and is a premium pollinator for Hall’s Giant, Istrian Round, and the American variety Ennis, while due to its late flowering it cannot be used for early varieties such as Istrian Long.

It grows as a moderately vigorous to vigorous shrub with a wide and branched canopy. Its main genetic and morphological characteristic is that it naturally forms an exceptionally large number of root suckers, which require regular removal if grown on its own roots. When grafted, it develops as an exceptionally stable, long-lived, and well-branched tree. It enters the fruiting stage early, in the third year after planting, and once it starts bearing, it produces regular, stable, and very high yields every year.

It belongs to the group of medium-late hazelnut varieties. In our region and under continental climatic conditions, it reaches harvest maturity at the end of August and during the first half of September.

Harvesting takes place at the end of summer and in early autumn. A major pomological and economic advantage of this variety is its exceptionally short husk, or involucre, which is split open and shorter than the nut itself. Due to this botanical trait, mature large nuts fall out of the husk completely easily and naturally, dropping massively directly to the ground, which greatly facilitates, speeds up, and reduces the cost of mechanical collection from the ground using vacuum harvesters, without the need for subsequent husking.

In a dry, cool, and well-ventilated space, well-dried in-shell nuts can be stored successfully for 6 to even 12 months without any loss of quality. Thanks to the firm shell, the kernel retains its ideal texture, freshness, and moisture content for considerably longer than when shelled.

The nut is large, with an average weight of 3–3.5 g, uniform on the tree, and characteristic in its distinctly recognizable roundish-flattened, slightly angular, and asymmetrical shape with a pronounced longitudinal seam. The shell is medium-thick, firm, smooth, and pale light brown to chestnut in color, with darker stripes. The kernel is large, light-colored, compact, sweet in taste, moderately rich in oils, and full in aroma. It has a good industrial kernel ratio of around 42–45%, and its pellicle separates from the kernel very easily and cleanly after roasting, or blanching, which makes it exceptionally popular and highly valued in both the domestic and global confectionery industry for producing premium chocolates, spreads, and hazelnut pastes, as well as for mass table consumption.

It is a moderately resistant variety. It is characterized by very high natural resistance of the wood and catkins to extremely low winter frosts and low temperatures during dormancy. In humid years before harvest, it requires preventive protection against hazelnut Monilinia fruit rot, Monilinia coryli, while among pests the greatest threats are the hazelnut weevil, Balaninus nucum, and phytophagous stink bugs, whose punctures cause the appearance of empty nuts and therefore require timely chemical protection.

The root system is surface-level and distinctly fibrous when grown from its own shoot, as a shrub, so it requires moderate moisture. When grafted onto Turkish hazel rootstock, however, it develops an exceptionally deep, powerful taproot that tolerates prolonged summer droughts extremely well, provides high tree stability, and completely prevents the appearance of root suckers, which drastically reduces orchard maintenance costs.

Our hazelnut plants are produced in two premium forms: as trained one- or two-year-old own-rooted shoots for bush-form cultivation, or as highly sought-after grafted hazelnuts on Turkish hazel rootstock, Corylus colurna, for tree-form cultivation, which guarantees easier mechanical cultivation and exceptional orchard longevity.