Like many people, my mother kept a bowl of nuts -- with nutcracker -- in the living room as both cool-season snack and autumn decoration. Although many plants have seeds large and tasty enough to eat, few are technically “nuts.”
The fruits of seed plants are divided into categories depending on specific characteristics of the fruit. (“Fruits” are what fertilized flowers develop into.) Both fleshy fruits and dry fruits are further divided according to which part of the original flower ovary develops into what shape around the seed. As with most seeds, the part animals relish is the cache of food the plant has stored to give its own offspring a good start.
Botanically, a “nut” is a large, single-seed fruit that doesn’t split open when mature and has a very hard outer shell formed by the ovary wall. Many nuts also are partially covered by a dry or papery husk and a few are completely covered by a dry husk.
Seeds of oaks, acorns are a classic nut: a hard shell around the seed with a hard, dry husk forming a cap around it. Oregon has a handful of native oaks, with at least one species representing each of the three major groups of oak -- white, red, and live. In general, oaks are groups by the shape of the leaves. White oaks have rounded lobes on deciduous leaves. Red (or black) oaks have pointed lobes on deciduous leaves. Live oaks have toothed, not lobed, leaves that remain on the tree year-round.
White oak acorns mature in a year; red/black oak acorns, with very-tight-fitting caps, mature in two years; our live oak acorns mature in two years.
Oregon white oak is the stately oak found through the Willamette Valley and most of inland western Oregon. Several red/black oaks or live oaks grow in inland reaches of southeastern Oregon, notably California black oak and canyon live oak.
The tanoak common in our parts of southeastern Oregon is in a different genus of the oak family. The sparsely toothed leaves of tanoak look like live oak leaves with clear valleys along the leaf veins; the caps of tanoak’s acorns are armed with spines.
Another member of the oak family found throughout western Oregon, chinquapin, has rather long and pointed evergreen leaves and very spiny nut husks.
Nearly all commercial filberts grown in the US are grown in Oregon’s Willamette Valley; these are European filberts. Closely related to the commercial filbert, is Oregon’s native hazelnut, the beaked hazel, which grows in western Oregon, Washington, and northern California, and in the northeastern US, the Great Lakes, and into parts of south-central Canada. Filberts and hazelnuts are members of the birch family with a dry, papery sheath tightly wrapped around the hard-shelled seed; the papery sheath in our native hazel extends far past the nut to form a long “beak,” completely hiding the nut. (In European filberts, the end of the nut peeks out of the sheath.)
Many of edible plant parts we call “nuts” may technically be something else. “Pine nuts” are seeds, of course, but not nuts. Most botanists categorize walnuts, pecans, almonds, coconuts, and others as “dry drupes” rather than true nuts because of the fleshy or fibrous husk around the hard seed (that is generally removed before we buy them). The “nuts” of Oregon myrtle also are drupes. Peanuts are legumes (in the pea or bean family), not nuts—their pods split to release the seeds within.
The seed’s store of starch and oil is often worth the hard work it takes to get through a nut’s hard, protective shell. Although prized by other animals, most acorns are bitter enough to require significant blanching or drying before people find them palatable.
I’ll decorate with the acorns, but I’ll eat the hazelnuts.
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Questions and comments about local natural history are welcome; gift certificates are available.