Corylus americana × avellana

Many of the Corylus clones now used for commercial nut production in North America derive from hybrids between the native American C. americana and clones of the European C. avellana (and/or C. maxima), combining the large and freely produced nuts of the latter group with the former species’ greater hardiness and, most importantly, its resistance to infection by Eastern Filbert Blight (EFB). The fullest introduction to this group is provided by Thomas Molnar in chapter two (Corylus) of Chittaranjan Kole’s Wild Crop Relatives: Genomic and Breeding Resources: Forest Trees (Heidelberg, 2011; Molnar 2011). The cross has not, as yet, thrown up any sports of particular ornamental interest.

The first person to try to hybridise Corylus americana and C. avellana seems to have been J.F. Jones, a nurseryman from Lancaster, Pennsylvania. In 1917, hazelnut culture in North America depended entirely on traditional clones introduced from western Europe, but the vulnerability of all of these plants to EFB meant that nut production was effectively limited to the Pacific coastal region – which EFB was not to reach for another half century. Jones selected an unusually prolific plant of C. americana from the local wild population, which was later to be widely planted in its own right under the clonal name ‘Rush’. Jones’ attempts to use ‘Rush’ as a pollen parent failed, but in 1919 he managed to use it as the seed-parent to produce hybrids with the European hazel clones ‘Barcelona’, ‘Cosford’, ‘Daviana’, ‘Italian Red’ and ‘Kentish Cob (known in the New World as ‘Duchilly’ or ‘Du Chilly’). After Jones’ death in 1928, his estate released the clones ‘Bixby’ (a cross with ‘Italian Red’) and ‘Buchanan’ (a cross with ‘Barcelona’ which is still in commerce).

A similar breeding programme was pursued by C.A. Reed of the Bureau of Plant Industry in Maryland, who used in addition to Jones’ ‘Rush’ the Corylus americana clones ‘Winkler’ and ‘Littlepage’. Two new selections, ‘Potomac’ (‘Rush’ crossed with ‘Kentish Cob’) and ‘Reed’ (‘Rush’ crossed with ‘Hall’s Giant’), were released in 1951. In the same year S.H. Graham of Ithaca, New York, released ‘Morningside’ (‘Rush’ crossed with ‘Kentish Cob’) and ‘Graham’ (‘Winkler’ crossed with the European hazel clone ‘Longfellow’). Carl Weschcke, in the harsh climate of Wisconsin, bred ‘Carlola’, ‘Delores’ and ‘Magdalene’, all of which were raised from a local wild selection of C. americana pollinated by a clone of C. avellana, ‘Brag’, which had been developed in British Columbia by another hazel breeder, Jack Gellatly. However, none of these clones proved reliably resistant to EFB, and few if any remain in cultivation (Molnar 2011).

Eastern Filbert Blight reached Oregon’s Willamette valley, the heartland of American hazelnut production, in the 1960s (Muehlbauer, Capik & Molnar 2021), prompting Oregon State University at Corvallis to embark on a large-scale breeding programme involving a variety of wild Corylus americana genotypes and multiple generations of hybrid descendants. In 2016, about fifteen Corvallis-bred fruiting hazels of hybrid origin were commercially available (USDA 2016). THE BEAST^® (‘OSU 541.147’) was patented in 2021 as the most promising Corvallis hybrid to date; it has a vigorous, upright habit and its rather small nuts fall free of their husks, as in C. avellana. The parentage was C. americana ‘Rush’ crossed with ‘Barcelona’, and ‘OSU 226.118’, itself bred at Corvallis from the C. avellana clones ‘Tombul Ghiaghli’, ‘Montebello’ and ‘Compton’ (Mehlenbacher & Smith 2021).

The greater prevalence of EFB in eastern North America, where wild Corylus americana provides a constant source of infection, has encouraged the development of even more reliably resistant (and cold-hardy) clones. Cultivars developed at Rutgers University in New Jersey – working closely with Corvallis – include ‘Raritan’ (a cross of two Corvallis clones, ‘OSU 539.031’ and ‘OSU 616.018’), ‘Monmouth’ (‘Sacajawea’, another Corvallis clone of European ancestry, crossed with ‘OSU 616.055’), ‘Hunterdon’ (‘Sacajawea’ crossed with ‘OSU 616.055’) and ‘Somerset’ (‘OSU 655.123’ crossed with the European clone ‘Ratoli’) (Muehlbauer, Capik & Molnar 2021).

Older selections, developed at the New York Agricultural Experiment Station and still recommended, include ‘NY 398’ (‘Gene’ or ‘Geneva’; ‘Rush’ crossed with the Old World ‘Red Lambert’), ‘Slate’ (‘Rush’ crossed with ‘Barcelona’ and named to honour George Slate who began hazelnut breeding at the Station in 1925), ‘Cheryl’ (‘Rush’ crossed with ‘Kentish Cob’) and ‘Linda’ (with the same parentage) (Muehlbauer, Capik & Molnar 2021).

At the Morden Experiment Station in the very cold climate of Manitoba, Canada, hazelnut breeding by Ernie Grimo has used wild C. americana selected in Saskatchewan, sometimes open-pollinated. Clones which were commercially available in 2021 from the Grimo Nut Nursery included ‘Kiara’, ‘Frank’, ‘Marion’ and ‘Joanne’. ‘Skinner’ used C. americana from the Hudson Bay area and the old European clone ‘Italian Red’; ‘Dermis’, an open pollinated seedling of ‘Skinner’, has better EFB resistance (Muehlbauer, Capik & Molnar 2021).