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Wisconsin Plant of the Week

Corylus cornuta Marshall

Betulaceae (Birch Family)

Common Name:

beaked hazelnut

07/28/2002

Beaked hazelnut, similar to the commercial filbert, is a deciduous native shrub that grows to 3 m tall often in the understory shade of oak and pine forests. It’s easily killed by fire but otherwise is tolerant of wide ranging conditions -- from full sun (where it produces many more nuts) to dense shade, and from dry sandy soil to the wetland edge. 

Separate male and female flowers bloom in early spring before the leaves open. The male flowers are in light brown catkins, 2 to 3 cm long, in clusters of 2 or 3 near the tips of last year’s twigs. The female flowers are hidden within dull gray scales, except for protruding threadlike deep red stigmas, an adaptation that helps protect the immature seed in cold weather. The fruit is a small edible nut enclosed in a bristly husk with a long tube-like beak that ripens to brown by late summer.

Hazelnut leaves are simple, alternate, oval with a round base and pointed tip and with doubly toothed margins. The veins in the leaves are straight and reach all the way to the margin. The zigzag twigs and leaf stalks are smooth.

Hazelnuts reproduce by seed and root suckers.  Propagation by seed requires racing the squirrels, who tend to strip the nuts before they’re ripe; keeping the nuts moist and planting promptly or cold-stratifying for several months.  After planting propagation suffers from a typically low germination rate and seedling predation.

Once shrubs are established the spring catkins are a protein source for grouse and woodcock.  Grouse, pheasants, turkeys, other birds and small mammals, eat and disperse the nuts.  Deer and rabbits browse the twigs in winter.

American hazelnut (C. americana), more common throughout Wisconsin, is very similar except for bristly twigs and leaf stalks, and smooth, round leafy bracts around the nut without the long beak.  Cultivated filberts, with the same taste but larger fruit than that of either native species, are C. colurna and C. maxima.

  • How to know the Birch Family:   All are woody trees or shrubs with simple, alternate leaves, with toothed margins.  Veins in the leaves are pinnate (like a feather), straight and reach all the way to the edge. At least the staminate flowers are in drooping catkins.  Other WI genera in the birch family -- birch (Betula), alder (Alnus), ironwood (Ostrya), musclewood (Carpinus)
  • Origin of the name: Corylus and cornuta both from the Greek, kornu.  The genus taken from the meaning “helmet”, for the shape and hardness of the shells; the species epithet from the meaning “having a horn or antler”
  • Range:  Northern N. Amer. , s. to ND, MI, and the Coastal Plain south to GA
  • WI Range:  Northern two-thirds of the State, south to Sauk and Sheboygan Counties
  • Common associates:  oaks, pines, aspens, spruce
  • Wetland Indicator Status: UPL
  • Coefficient of Conservatism:  WI, 5; MI, 5; Chicago Region, 10 (presumed extirpated)
     
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