Hybrid Hazelnut (corylus heterophylla etc)

They are a cross of American and European hazelnuts. While the nuts are a bit smaller than European hazelnuts, their American genetics provide more hardiness to the Eastern Filbert Blight, and improved cold hardiness.
 
Aldara Seedlings: Super cold hardy selection bred by Grimo Nut Nursery in Canada. According to Grimo, they are early bearing, blight resistant and have good kernel quality.
 
Wisconsin Seedlings: Another Grimo source - these are hybrids crossed with European hazels with years of exposure to the Wisconsin & Minnesota climate. They are productive trees with moderately thick shells. There is variation in tree size, nut size and the ease of husking.  
 
Mature tree size is about 10-14 ft tall and wide. Hardy to zone 3b, possibly 3a.
 
See guides from University of Wisconsin-Madison for more information on growing hazelnuts!