European hazelnut flowers can survive down to at least 10F (-12.2C), and when fully elongated, their catkins down to 15F (-9.4C).  Regardless, they are still vulnerable to frost damage, since they awaken quite early.  Only the most blight resistant, late blooming varieties should be planted in most of the US.

American hazelnuts are better adapted to hot summers and cold winters, as well as late frost, but the nuts are very small and the bush suckers quite a bit.  However, they may develop nice fall colors in locations other hazelnut species will not.

European Hazelnut
Corylus Avellana

Barcelona

🔍
Zone
• 4 (5)
Blooms
💮
• early
Ripens
🌰
• late
Fruit
• 3.3-3.8g/nut, 39-43% kernel, 70-85% have good nuts
Yield
• moderate cumulative and efficiency yield
Afflictions
• Resistant to bud mite.
Highly susceptible to eastern filbert blight.

Barcelona is the standard commercial cultivar, but it is being replaced by Jefferson.

Delta

🔍
Released in Oregon (2002).
Zone
• 4 (5)
Blooms
💮
• mid
Growth
• likely smaller than Barcelona
Afflictions
• Resistant to eastern filbert blight.  At least somewhat resistant to bud mite.

Dorris

🔍
OSU 309.074 (Tonda Gentile delle Langhe x OSU 23.017 (Barcelona x Extra Ghiaghli)) x Delta.  Developed in Oregon.  Released in 2011.
Zone
• 4
Blooms
💮
• mid    ◦ ~2 weeks after Barcelona
Ripens
🌰
• late    ◦ similar time as Barcelona
Growth
• 60% of Barcelona
Fruit
• 3.37g/nut, 43% kernel
Yield
• moderate cumulative yield, high efficiency yield
Afflictions
• At least somewhat resistant to eastern filbert blight and bud mite.

Dorris is as productive as Barcelona but is quite efficient due to being 60% of the size.

Ennis

🔍
Zone
• 4 (5)
Ripens
🌰
• late    ◦ ~0 to 0.5 weeks after Barcelona
Growth
• 60-70% size of Barcelona
Fruit
• 3.1-4.6g/nut, 43-46% kernel
Yield
• high cumulative and efficiency yield
• may have double the usual nut defects some years
Afflictions
• Highly susceptible to eastern filbert blight.

Epsilon

🔍
Released in Oregon (2002).
Zone
• 4 (5)
Growth
• ~70% of the size of Barcelona or less.
Afflictions
• Resistant to eastern filbert blight (may be highly resistant).

Eta

🔍
Zone
• 4 (5)
Blooms
💮
• late
Ripens
🌰
• late    ◦ ~0 to 0.5 weeks after Barcelona
Growth
• 75% of the size of Barcelona
Fruit
• 2.8g/nut, 48% kernel
Yield
• moderate cumulative yield? low efficiency yield?
Afflictions
• At least somewhat resistant to eastern filbert blight.  Somewhat resistant to bud mite.

Felix

🔍
OSU 384.095 (Casina x OSU 55.129 (Tonda Gentile delle Langhe x Extra Ghiaghli)) x Delta.  Developed in Oregon (1999).
Zone
• 4
Blooms
💮
• mid-late
Ripens
🌰
• mid-late    ◦ ~1 to 1.5 weeks before Barcelona
Growth
• as large as Barcelona
Fruit
• 2.65g/nut, 50% kernel
• nut defects appear to be quite low
Yield
• less productive than Barcelona
Afflictions
• At least somewhat resistant to eastern filbert blight.  Somewhat resistant to bud mite.

Gamma

🔍
Released in Oregon (2002).
Afflictions
• Resistant to eastern filbert blight.

Jefferson

🔍
Zone
• 4 (5)
Blooms
💮
• late
Ripens
🌰
• late    ◦ similar time as Barcelona
Growth
• 70% of the size of Barcelona
Yield
• moderate cumulative yield, higher yield efficiency than Barcelona
Afflictions
• At least somewhat resistant to bud mite.
Somewhat susceptible to eastern filbert blight.

Jefferson is being used to replace Barcelona as the main commercial producer due to its equivalent or slightly better nut quality, higher yield efficiency, and lower susceptibility to eastern filbert blight (EFB).  While it performs quite well west of the Rockies, where more effective strains of EFB aren't present, it may not have enough resistance to thrive in the east.

Lewis

🔍
Developed in Oregon
Zone
• 4 (5)
Blooms
💮
• mid
Ripens
🌰
• mid-late    ◦ ~0.5 to 1 weeks before Barcelona
Growth
• 75% of Barcelona
Fruit
• 2.8g/nut, 46-48% kernel
Yield
• high cumulative and efficiency yield
Afflictions
• Resistant to bud mite.
Susceptible to eastern filbert blight.

Mcdonald

🔍
Tonda Pacifica (Tonda Gentile delle Langhe x OSU 23.024 (Barcelona x Extra Ghiaghli)) x Santiam.  Developed in Oregon (1998).
Zone
• 4
Blooms
💮
• mid
Ripens
🌰
• mid    ◦ ~2 weeks before Barcelona
Growth
• 75-85% of Barcelona
Fruit
• 2.5g/nut, 51.5% kernel, low number of defects
Yield
• Moderate cumulative yield, moderate-high efficiency yield
Afflictions
• At least somewhat resistant to eastern filbert blight.  Somewhat resistant to bud mite.

Sacajawea

🔍
Released in Oregon (2006).
Zone
• 4 (5)
Blooms
💮
• mid
Ripens
🌰
• mid (mid-late)    ◦ ~1 to 2 weeks before Barcelona
Growth
• 85% of Barcelona
Fruit
• 2.8g/nut, 48-50% kernel
Yield
• high cumulative and efficiency yield
Afflictions
• Resistant to bud mite.
Susceptible to eastern filbert blight.

Theta

🔍
Released in Oregon (2009).
Zone
• 4 (5)
Blooms
💮
• late
Ripens
🌰
• late    ◦ ~0 to 1 week after Barcelona
Growth
• similar to Barcelona
Fruit
• 2.3g/nut, 50% kernel
Yield
• low cumulative and efficiency yield
Afflictions
• Somewhat resistant to eastern filbert blight and bud mite.

Tonda Di Giffoni

🔍
Popular in Italy, probably originated there.
Zone
• 4 (5)
Blooms
💮
• mid
Ripens
🌰
• late    ◦ same time as Barcelona
Growth
• 55% of Barcelona
Fruit
• 2.7 to 3.2g/nut, 45-50% kernel
• slightly more nut defects than some of the newer varieties
Yield
• moderate cumulative yield, high efficiency yield
Afflictions
• Resistant to bud mite.
Susceptible to eastern filbert blight.

Tonda Pacifica

🔍
Tonda Gentile delle Langhe x OSU 23.024 (Barcelona x Extra Ghiaghli).  Developed in Oregon (1982).
Zone
• 4 (5)
Blooms
💮
• mid season or earlier
Ripens
🌰
• mid-late    ◦ ~1 to 1.5 weeks before Barcelona
Growth
• smaller than Barcelona
Fruit
• 2.24g/nut, 47% kernel
• fewer defects than Barcelona
Yield
• moderate cumulative yield, high efficiency yield
Afflictions
• May have some resistance bud mite.
Highly susceptible to eastern filbert blight.

Wepster

🔍
Tonda Pacifica x OSU 440.005.  Developed in Oregon (1998).
Zone
• 4
Blooms
💮
• mid
Ripens
🌰
• mid-late    ◦ ~1 to 1.5 weeks before Barcelona
Growth
• 80-110% of Barcelona
Fruit
• 2.39g/nut, 43.9% kernel
Yield
• high cumulative and efficiency yield
Afflictions
• At least somewhat resistant to eastern filbert blight.
Somewhat susceptible to bud mite?

Yamhill

🔍
Zone
• 4 (5)
Blooms
💮
• mid
Ripens
🌰
• mid (mid-late)    ◦ ~1 to 2 weeks before Barcelona
Growth
• 60-70% of Barcelona
Fruit
• 2.3g/nut, 49% kernel
• may produce a fairly high number of defects
Yield
• high cumulative and efficiency yield
Afflictions
• Somewhat resistant to eastern filbert blight.
Somewhat susceptible to bud mite.

York

🔍
OSU 479.027 x OSU 504.065.  Developed in Oregon (1998).
Zone
• 4
Blooms
💮
• mid    ◦ ~2 weeks after Barcelona
Ripens
🌰
• mid-late    ◦ ~0.5 to 1.5 weeks before Barcelona
Growth
• 75% of Barcelona
Fruit
• 2.73 to 2.85g/nut, 46% kernel
Yield
• moderate cumulative and efficiency yield
Afflictions
• At least somewhat resistant to eastern filbert blight.  May have some resistance to bud mite.

American Hazelnut
Corylus Americana

Skinner

🔍
Originated in Manitoba, Canada.
Zone
• 3a
Blooms
💮
• very late?
Ripens
🌰
• early    ◦ 70 to 90 days after pollination
Growth
• 4-6ft in height
Fruit
• slightly larger than the average american hazelnut
Afflictions
• Somewhat resistant to eastern filbert blight.

Skinner produces few runners.

Winkler

🔍
Originated in Iowa, introduced in 1918.
Zone
• 3
Blooms
💮
• very late?
Growth
• 6ft in height
Fruit
• slightly larger than the average american hazelnut
Afflictions
• Resistant to eastern filbert blight.

Hazelnut
(hybrid)

Badgersett Seedlings

🔍
C. americana, C. cornuta, and C. avellana parentage
Zone
• 4 (3)
Afflictions
• Most seedlings appear to be at least somewhat resistant to eastern filbert blight.

Badgersett Farm sells seedlings from multi-generation, improved hybrid selections.

Precocious

🔍
C. avellana x C. americana
Zone
• 4a (3)
Blooms
💮
• late
Afflictions
• At least somewhat resistant to eastern filbert blight.

'Precocious' appears to generally refer to a strain of seedlings rather than a variety.