Jefferson was developed and evaluated at Oregon State University in Corvallis, Oregon, and was released in January 2009. This variety combines very high
resistance to eastern filbert blight (EFB) caused by the fungus Anisogramma anomala (Peck) E. Müller with large nut size, good kernel quality, and high yields. ‘Jefferson’ was released for the in-shell market as an EFB-resistant replacement for ‘Barcelona’. Kernel quality is suitable for many end-uses.
Jefferson is suitable for planting in areas with high EFB disease pressure.
Tree growth and habit
Jefferson trees are a little smaller and have a slightly more upright growth habit. Trees are moderately vigorous and have an upright, spreading canopy. They will be easy for growers to manage with occasional pruning. In other hazelnut cultivars, good light penetration into the canopy has been shown to increase nut set, nut size, and kernel size and reduce the occurrence of single-nut clusters that are common inside densely shaded canopies. Tree size is estimated by measuring the trunk crosssectional area at 30 cm from the soil line.
this estimate, ‘Jefferson’ trees are 30%–40% smaller than the vigorous standard ‘Barcelona’ and 5%–10% smaller than ‘Lewis’. When canopy width and height were measured in the ninth leaf, ‘Jefferson’ was 15% smaller than ‘Barcelona’ in both height and width. There was less than 10% difference in
canopy height and spread between ‘Jefferson’ and ‘Lewis’. Tree anchorage is strong, and no tendency to lean has been noted. During the 8-year evaluation period, trees were irrigated regularly for the first 5 years. Establishment and performance of this cultivar under dry conditions have not been tested.
Basic requirements Filberts are hardy plants which can survive adverse growing conditions. They should be grown in a soil which is at least 2.4 to 3 m (8-10 ft) deep and will grow optimally in well-draining, fertile loams with a pH between 5.5 and 7.5 in full sun or partial shade. Filberts will grow well in areas where wild hazel grows large and vigorous.
Propagation methods While it is possible to propagate filberts from cuttings, the success rate for obtaining rooted cuttings is usually only between 20 and 50%. The most successful method of propagating filberts is by layering. The most successful and widely used method of layering for commercial filbert production is tip layering.
Tip layering involves bending shoots into a V-shape and burying the lower parts in the soil to a depth of 20 to 25 cm (8-10 in) while the tips of the shoot, which will form the new tree tops, are kept upright. The soil is kept moist to promote root development above the V bend on the tip and roots should ideally be congregated in a 5 to 10 cm (2-4 in) section of the shoot.
Planting Trees should be planted in early winter while dormant. The trees should be planted at least 6 m (20 ft) apart.
Before planting, remove as much as possible of the old layered shoot and prune back the ends of any broken roots. Plant the tree in a hole large enough to accommodate the roots but avoid deep planting. Fill in the hole around the roots with fine soil, pressing down with your hands to eliminate any air pockets around the roots. Add soil on top of the roots and tamp down to set the tree. Fill in the remainder of the hole with loosely packed soil.
Once planted, the tree should be headed back in order to compensate for reduced water uptake. the tree should be cut back to a height of 45 to 76 cm (18-30 in). Suckering Hazelnut trees produce suckers which should be removed from the tree at, or close to, their point of origin on the trunk. This can be achieved by gently removing the soil from around the sucker. While the trunk is exposed, any other buds which are beginning to show should also be removed.
Cutting the sucker at or just below the soil line will encourage more suckers so it is important to make the cut as close to the trunk as possible. Harvesting Newly planted trees usually bear nuts within two to three years after planting although full production may not be reached until twenty five years after planting. The nuts are usually harvested two to three times over the season. The nuts can be spread out on the ground to dry or, as with commercially produced nuts, dried artificially at a temperature of 90 to 100°C (176-212°F).