June 9, 2012

Corylus sp. - Hazel, Filbert




    Members of genus Corylus grow wild throughout temperate North America, Asia and Europe.  Corylus contains 15 to 20 species of shrubs and trees, including two which the USDA considers “commercial cultivars”: C. colurna and C. maxima, also known as filberts (Whitcher and Wen 2001: 283, Nesom 2007).  The two North American species, C. americana and C. cornuta, were very important foods throughout prehistory.   North Americans used hazelnuts for both food and medicine.  They were eaten raw, used as a base for soup, and processed to produce dermatological aids, emetics, remedies for cramps, respiratory aids and, by the Iroquois, a special wash used to treat loneliness (Moerman 2009:158-9). 


    Both species of North American hazel produce fruit in late summer every two to three years.  Fresh fruits are most easily differentiated on the basis of the shape of their involucres (a cup-like structure or bract enveloping the apex of the nut): C. americana has a flat, fringed involucre and often appears in clusters, whereas C. cornuta has a long beaked involucre and occurs singly or in pairs.  Nuts of C. americana are distinguishable on the basis of their truncate apex, even without an involucre. C. americana nuts are also slightly larger, averaging 15 X 12 X 10 mm, whereas C. cornuta averages 13 X 12 X 10 mm.  Both nuts are smooth with slight ridges running from the apex to the base (Montgomery 1977: 57; Figure 1).

Figure 1: Top: C. cornuta;  Bottom: C. americana

   Archaeologically, hazelnuts are usually identified based on fragments of nutshell (pericarp) which are quite distinctive and easy to differentiate from other kinds of nutshell commonly recovered in the Eastern Woodlands.  The shells are less than 2 mm thick and are formed by two distinct layers.  The outer layer is thinner.  Parallel ridges run from the apex to the base of the nut.  These can be seen in cross section as circular voids between the two layers of the shell.  This feature is almost always visible on archaeological fragments, and is common to both North American species.  Fragments of the inner nutshell also bear parallel striations that allow identification even if the outer layer is not present (Figure 2).  

Figure 2: Experimentally carbonized fragments of modern C. americana nutshell. Top: Double layered pericarp with parallel ridges; Bottom: profile of pericarp with circular voids between two layers

Archaeological Distribution

    In the Eastern Woodlands, hazelnuts were used alongside hickory and walnut from at least the Early Archaic, but are less abundant than these other staple nut crops in the archaeological record for most time periods.  Exceptions to this rule, as in the European Mesolithic, have been argued to indicate times of intensive land clearance and incipient agriculture.  During the Middle Woodland  in the American Bottom and Illinois River Valley,  hazelnut shell abundance increases sharply in archaeological contexts and is more frequently recovered than in any other time period (Simon and Parker 2006:224).  In the Eastern Woodlands, hazelnut shell is usually identified as Corylus americana, because this species is much more common in these areas today.  Corylus cornuta  is completely absent in Indiana, Missouri, and the lower Mississippi. Criteria for distinguishing between species from fragments of nutshell are not established.  In the west, Corylus cornuta var. californica was an important resource along the California coast and in the Pacific Northwest (Hammett and Lawlor 2004; Lepofsky 2004).  
The Plant and its Modern Distribution

Native hazels are present throughout the United States with the exception of Texas, New Mexio and Arizona, Nevada, and Utah.  C. americana does not grow west of the Great Plains. C. cornuta is separated into eastern and western subspecies, but it does not grown in the midsouth and parts of the midwest.   Hazels prefer sun or partial shade, tending to form thickets on disturbed ground close to streams.  They may also form the understory in forests, especially those with fairly open canopies.  American hazels begin to produce nuts in their first year, and will produce a good crop every two or three years thereafter (Nesom 2007).  Hazels rely on small, scatter-hoarding mammals for seed dispersal, but humans have also played a role in their success and spread.  The relationship between hazel and fire, whether natural or human-induced, is well established.  For example, one study which compared undisturbed timber stands to recently burned stands in the Turtle Mountains of North Dakota found that the incidence of hazel in the burned stands had increased by nearly 25%.  Although studying drastic changes in the overall plant community, the authors assert: “The most obvious influence of fire is the increase in relative cover of Corylus cornuta [beaked hazel]…” (Potter and Moir 1961:476).


The record establishing hazel species as human camp followers and food sources stretches back into the Terminal Pleistocene (Cunliffe 1994:109-110; Palmé and Vendramin 2002).  In addition to their widely accepted tastiness, hazelnuts are extremely nutritious and useful. Hazelnuts are 60% fat by fresh weight, a property which would have made them attractive to human foragers.  They are also high in unsaturated fats and phytoserols, both of which are known to reduce incidence of high blood pressure and heart disease (Amaral et. al. 2006:274-5).  Extracts of American hazelnuts are also used as emollients (Nesom 2007), while their branches are ethnographically known to have been used for basketry by American Indians (Kindscher and Hurlbut 1998).  Human land clearance in temperate forests, especially by fire, will create favorable habitats for hazel species and tend to increase the availability of their nuts as a food crop.  In most places and times where hazels are available, humans have used their nuts, branches, and leaves for food, crafts, or medicine.


Amaral, Joana S. , Susana Casal, Ivana  Citov´a, Alberto Santos, Rosa M. Seabra, and Beatriz P. P.  Oliveira
      2006            Characterization of Several Hazelnut (Corylus avellana L.) Cultivars Cased in  Chemical, Fatty Acid and Sterol Composition. European Food Research and Technology 222:276-80.

Cunliffe, Barry
1994    The Oxford Illustrated History of Prehistoric Europe. Oxford University Press, New York.

Hammett, Julia E., and Elizabeth J. Lawlor
2004    Paleoethnobotany of California. In People and Plants in Ancient Western North America, edited by Paul E. Minnis, pp. 278-366.  Smithsonian Books, Washington, DC.

Kindscher, Kelly, and Dana P. Hurlburt
    1998    Huron Smith's Ethnobotany of the Hocą (Winnebago). Economic Botany 52(4):352-72.

Lepofsky, Dana
2004    Paleoethnobotany in the Northwest. In People and Plants in Ancient Western North America, edited by Paul E. Minnis, pp. 367-464. Smithsonian Books, Washignton, DC.

Moerman, Daniel E.
2009    Native American Medicinal Plants: An Ethnobotanical Dictionary. Timber Press, Portland.

Montgomery, Frederick H.
1977    Seeds and Fruits of Plants of Eastern Canada and Northeastern. University of Toronto Press, Toronto.

Nesom, Guy
2007    Plant Guide: American Hazelnut (Corylus americana Walt.). Natural Resources Conservation Service. Electronic Resource, http://plants.usda.gov/plantguide/pdf/pg_coam3.pdf, accessed May 1, 2012.

Palmé , A.E., and G.G. Vendramin
2002    Chloroplast DNA variation, postglacial recolonization and hybridization in hazel, Corylus avellana. Molecular Ecology 11:1769-79.

Potter, Loren D,. and D. Ross Moir
1961    Phytosociological Study of Burned Deciduous Woods, Turtle Mountains North Dakota. Ecology 42(3):468-80.

Simon, Mary L., and Kathryn E. Parker
2006    Prehistoric Plant Use in the American Bottom: New Thoughts and Interpretations. Southeastern Archaeology 25(2):212-57.

Whitcher, Ixchtel N., and Jun Wen
2001    Phylogeny and Biogeography of Corylus (Betulaceae): Inferences from ITS Sequences. Systematic Botany 26(2):286-98.

Written by Natalie G. Mueller