For ordinary purposes the nuts sold commercially, whether imported or grown in this country, are called filberts while those nuts which may be found growing prolifically in woodlands and pastures over almost the whole United States but which are not to be found on the market are called hazelnuts.  This lack of commercialization of hazelnuts should be recognized as due to the smallness of the nut and the thickness of its shell rather than to its lacking flavor.  Its flavor, which seldom varies much regardless of size, shape or thickness of shell, is both rich and nutty.  The three main food components of the hazelnut, carbohydrate, protein and oil, are balanced so well that they approach nearer than most other nuts the ideal food make-up essential to man.  The English walnut contains much oil and protein while both chestnuts and acorns consist largely of carbohydrates.

One salient feature which definitely separates the species Corylus Americana or wild hazel, from others of its genus, is its resistance to hazel blight, a native fungus disease of which it is the host.  Controversies may occur over the application of the names “hazel” and “filbert” but there is no dispute about the effect of this infection on members of genus Corylus imported from Europe.  Although there is wide variety in appearance and quality within each of the species, especially among the European filberts, and although filberts may resemble hazels sufficiently to confuse even a horticulturist, the action of this fungus is so specific that it divides Corylus definitely into two species.  Corylus Americana and Corylus cornuta, through long association, have become comparatively immune to its effects and quickly wall off infected areas while filbert plants are soon killed by contact with it.  Hybrids between filberts and hazels will usually be found to retain some of the resistance of the hazel parent.

The ideal nut of genus Corylus should combine qualities of both hazels and filberts.  Such a hybrid should have the bushy characteristics of the American hazel with its blight-resisting properties and its ability to reproduce itself by stolons or sucker-growth.  It should bear fruit having the size, general shape, cracking qualities and good flavor of the filbert as popularly known.  The hybrids I am growing at my farm, which I call “hazilberts” and which are discussed later, seem to fulfill these requirements.  The plants may be grown as bushes or small trees.  They are blight-resistant and their nuts are like filberts in appearance.  Three varieties of these hazilberts have ivory-colored kernels which are practically free of pellicle or fibre.  They have a good flavor.

A comparison of the ripening habits and the effect of frost on the various members of the genus Corylus growing in my nursery in the fall of 1940, is shown by these extracts taken from daily records of the work done there.  It should be noted that the summer season that year was rainy and not as hot as usual, so that most nuts ripened two to three weeks later than they normally do.