Jefferson Filbert Hazelnut Tree

Corylus avellana 'Jefferson' (OSU 703.007) is an Oregon State University hazelnut cultivar released in 2009 for large nuts, good kernel quality, and high yields ([OSU Jefferson profile](https://agsci.oregonstate.edu/hazelnuts/jefferson-hazelnut)). Its production and pollination details are cultivar-specific, so retain the exact Jefferson identity when planning a crop. ## Crop and pollination OSU lists Gamma, Eta, and Theta as pollinizers for Jefferson, with recommended proportions of 10%, 30%, and 60%, respectively ([OSU Jefferson profile](https://agsci.oregonstate.edu/hazelnuts/jefferson-hazelnut)). These are OSU production recommendations; use current local extension guidance for orchard or garden spacing and bloom overlap. OSU reports large nut size, good kernel quality, and high yield ([OSU Jefferson profile](https://agsci.oregonstate.edu/hazelnuts/jefferson-hazelnut)). ## Size and disease An OSU nine-year specimen measured 3.33 metres tall with a 3.0-metre canopy spread; this is an observed plant, not a universal mature-size guarantee ([OSU Jefferson profile](https://agsci.oregonstate.edu/hazelnuts/jefferson-hazelnut)). The cultivar profile describes very high resistance to eastern filbert blight (EFB), but a later OSU alert reports aggressive EFB infections in Jefferson and other historically resistant cultivars in part of the northern Willamette Valley ([OSU Jefferson profile](https://agsci.oregonstate.edu/hazelnuts/jefferson-hazelnut); [OSU EFB alert](https://extension.oregonstate.edu/catalog/potential-new-aggressive-efb-strain-infecting-resistant-hazelnut-varieties)). Resistance should not be treated as immunity. ## Maintenance Allow enough room for a fruiting hazelnut and compatible pollinizers. Monitor for local EFB pressure and follow current regional recommendations for disease management and crop care ([OSU EFB alert](https://extension.oregonstate.edu/catalog/potential-new-aggressive-efb-strain-infecting-resistant-hazelnut-varieties)). Monitor for local EFB pressure and follow current regional recommendations for disease management and crop care.