Corylus colurna L.

Corylus colurna is the only tree-sized hazel whose natural distribution extends west into Europe. Its nuts taste similar to those of the common European Hazel C. avellana, but are slightly smaller and thicker-shelled and are protected until they drop within a much more elaborately lobed husk with a ruff of spreading, leathery points. In terms of habit it typically differs from C. avellana about as drastically as two trees can: young Turkish hazels can be almost [Larix]-like in winter, with a straight trunk carrying a spire-shaped crown on light, slender limbs – a habit highlighted by the remarkable natural pallor of the winter twigs, and complemented in February by the strict verticals of the long and generally abundant male catkins. Mature trees retain a few much bigger limbs which can carry a broadly domed crown, but still with a good straight bole. Just a few fork or branch heavily from the base.

This is an easy tree to grow, tolerating drought and cold and not bothered much by the soil so long as it is not waterlogged. As such it has long been cultivated outside its native heartlands in the Near East and the mountains of the Balkans; one at Alland in lower Austria is believed to have been planted around 1560 and in 2021 had a long trunk 102 cm broad (monumentaltrees.com 2023). The species reached England around this time, via the imperial medicinal garden in Vienna where it was grown by Charles L’Ecluse (Clusius), and by the 1660s John Ray was growing ‘many goodly trees’ grafted onto Corylus avellana (Johnson 2015). There are no surviving trees in the UK this old – this is a species less well adapted to the mild and moist conditions of the Atlantic fringe – but two which were already big when recorded by Henry Elwes and Augustine Henry more than a century earlier (Elwes & Henry 1906–1913) still survive as rugged, domed specimens at Syon in west London and in a private corner of Wollaton Park in Nottingham (Tree Register 2023). An old but rather dumpy tree grows as far north as Dundee’s Baxter Park, while the species’ hardiness is demonstrated by its cultivation since 1976 at the Linnaeus Garden at Uppsala in central Sweden (Royal Botanic Garden Edinburgh 2023). Another planted in the mid 1960s has thrived as well as any tree at the Stanmer Park Arboretum near Brighton, England, a collection planted to test the performance of hundreds of potential street trees in the most free-draining and reactive of chalky soils.

All these qualities have recommended C. colurna in recent decades as a near-perfect street tree. (The only perfect street tree, of course, is one that is different from any other tree in its street and can therefore be guaranteed to perform best when faced by at least one potential combination of novel pathogens and shifting weather-patterns.) The formal habit also suits this hazel for planting in large avenues, though there are not as yet many examples. Seed-raised examples can be so consistently cone-shaped – in youth – that few named selections have been made.

There do not seem to have been many recent re-introductions to the west of what is already a widely-grown plant. Hørsholm Arboretum in Denmark grows a good tree from seed collected in Macea, Romania, by the Botanical Garden of the University of Lasi (University of Copenhagen 2023).

In North America, the popularity of any hazel is likely to be compromised by the presence of Eastern Filbert Blight (EFB), to which only the two native bushes are reliably resistant. Corylus colurna remains much less well-known and widely available than it is across Europe, though it is more likely to resist EFB than C. avellana or than many of the nut-producing clones derived from this species (Capik & Molnar 2012).

The nuts’ small size and thick shells are factors which have discouraged the use of C. colurna in breeding nut trees. However, the roots can provide a non-suckering stock onto which scions of all fruiting hazels can easily be grafted, and are often used for this purpose. The rather slow establishment from seed of C. colurna may lead to its replacement as a commercial rootstock by the related Corylus chinensis (Cerović et al. 2009; Rovira 2021; Bijelić et al. 2021). Turkish Hazel also produces a good timber, which is dense and beautifully tinged pink and is used in joinery (Čokeša et al. 2020); Linnaeus’ species name derives from the classical Latin for a kind of hazel with useful wood, rather than nuts.