American Hazelnut in Winter

Winter in the Central Piedmont of North Carolina has been cold and windy, with below average temperatures and bursts of damaging winds. In the City of Raleigh, consecutive low temperatures of 9, 15, and 25 degrees Fahrenheit were recorded in early January.  These unusually low temperatures have had a stunting affect on a number of our native southern species.  However Corylus americana, the American Hazelnut, whose natural range extends deep into the Canadian Provinces, is unaffected by these conditions. Hazelnuts are extremely cold-hardy, even blooming during the winter when most shrubs are dormant . In the Falls Lake area, American Hazelnut usually blooms sometime in February. The winter bloom is thought to aid wind pollination since leaves are not on the trees and shrubs to block the wind-born pollen grains.
Below are photos of American Hazelnut male catkins and female flowers. The red ribbon-like structures in the female flowers are the styles. In the first photo, 4 small female flowers can be seen.

Corylus Americana Male Catkins and Female Flowers

Corylus americana
Male Catkins and Female Flowers

Corylus americana Female Flower

Corylus americana
Female Flower

American Hazelnuts are large, multi-stemmed shrubs that form small colonies. Although they are uncommon in the Falls Lake area, the absence of dense foliage in the winter makes them easier to spot from trails and greenways. The next photo shows a cluster of mature American Hazelnut stems in a small, isolated colony near a stream.

Corylus americana Multiple Stems

Corylus americana
Multiple Stems

The most important mode of reproduction is underground rhizomes, giving rise to young shoots that grow and mature near the parent plants. In the next shot, most of the older stems of this American Hazelnut are bent badly, but clusters of new shoots can be seen all around the older stems.

Corylus americana Multiple Stems and Shoots

Corylus americana
Multiple Stems and Shoots

When conditions are favorable, large numbers of shoots can form dense thickets. Native Corylus species are credited with playing an important role in soil conservation due to their strong and complex root systems.

Corylus americana Thicket

Corylus americana
Thicket

Corylus americana is a remarkably glandular plant, not only in the spring and summer, but even in the dead of winter. This twig was photographed just after the coldest period this area experienced in early January.

Corylus americana Twig Stipitate Glands

Corylus americana
Twig Stipitate Glands

The stalked glands emerging from the twigs are known as stipitate glands. The term stipitate is derived from the botanical term stipe, which is a stalk that supports another structure. So stipitate glands are simply glands on the ends of stalks. It is believed that glands such as these evolved as a means for plants to transport and store secretions (with potentially toxic by-products) outside the plant body where they can serve as a first line of defense on the surface of the plant. Stipitate glands are also a useful tool in differentiating Corylus americana from its close relative Corylus cornuta, the Beaked Hazelnut, which does not have stipitate glands. These glands are very obvious on spring foliage and do not require magnification to be seen. They can even be seen on the bracts of the nuts in the late summer and fall, as the following shot illustrates.

Corylus americana Bract with Stipitate Glands

Corylus americana
Bract with Stipitate Glands

 American Hazelnut is sometimes confused with the more common Smooth Alder – Alnus serrulata  –  a similar multi-stemmed, clumping shrub with winter catkins and early blooming female flowers. Both Smooth Alder and American Hazelnut are members of the birch family (Betulaceae) and are found in similar locations, sometimes directly adjacent to each other.

In the Falls Lake area, the catkins of Smooth Alder are often reddish purple until they bloom, and the female flowers are in upright clusters at the tips of the twigs, bearing no resemblance to the flowers of American Hazelnut.  The fruits persists into the winter and appear like little pine cones suspended above the male catkins.

Alnus serrulata Winter Male Catkins

Alnus serrulata
Winter Male Catkins

Alnus serrulata Female Flowers

Alnus serrulata
Female Flowers

Alnus serrulata Winter Fruits

Alnus serrulata
Winter Fruits

The nuts of Corylus americana are edible and are considered a delicacy by many, although their small size means that few are planted for commercial purposes.  A European cousin, Corylus avellana, is the main source of commercially produced Hazelnuts in the U.S.  The vast majority are grown in the Northwest U. S.  This species is also becoming an important source of Taxol, a critically important cancer drug.  The discovery of Taxol in Hazelnuts has a role in conserving rare Yew species, such as the Pacific Yew, which was originally the only source of Taxol.

Herb Amyx

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