Life of a Hickory Tree Part 1

Oak-Hickory Forest found in Eastern Iowa.  The red trees are oaks and the yellow trees Shagbark Hickory.

This is the first of a four part series on the Shagbark Hickory tree of the Oak-Hickory Forest found in the Midwestern and Eastern United States.  It is sort of a continuation of the Life of an Oak blogs posts from last fall.  

In upland Oak-Hickory forests oaks draw all the attention and excitement.  Typically, oaks are larger and more abundant, but it takes hickory trees to make an Oak-Hickory forest of course.  Hickories have very similar life histories when compared to oaks of the Eastern and Midwestern United States, and this is exactly why oaks and hickories are closely associated.  The hickory however, is more of a forest species and indicates another step in transition from prairies more common to the west, to forests more common to the east.  In the Midwest, where this prairie to forest transition takes place, the Shagbark is the most common hickory of this forest type.  When first settled in the mid-1800's the Shagbark was an extremely minor tree in oak savannas but more common in oak woodlands, especially in slightly moister areas where fires burned less frequently.  Settlers made quick use of the hickory trees, chopping them down and using them to build strong tools and for burning.  Savanna and woodland oaks however, were often too large to cut down with ordinary 1800's era tools but the smaller hickories were much easier to cut and process.  For this reason, and because they were less common in the first place, hickories vanished far before oaks did.  As a result, hickories may be in lower proportions even today in oak forests.  Today however, I have seen an abundance of young hickories in oak forests, making me think their populations are growing in some areas.  Fire suppression in the modern era may be contributing to this increase of hickories as well as a normal repopulation of areas where hickories historically were completely eliminated by logging. 

Life as a nut

For hickories, life begins with what most of us would consider a nut.  Scientists however tell us that hickory nuts are not in-fact nuts, rather they are fruit.  Let me explain.  First of all, a fruit is any plant structure that contains seed.  Nuts on the other hand are simply a large dry seed enclosed in a dry shell.  While the hickory does have a large dry seed enclosed in a dry shell, early in its life this nut is enclosed in fleshy, or should I say fruity, plant material.  As the seed matures this fleshy container hardens into a dense woody shell that even the most pesky of squirrels can't penetrate.  Traditional ideas of succulent sweet fruit does not fit the hickory nut fruit.  This dense husk like flesh protects the hickory seed extremely well as it grows on the tree through summer.  However, as if to say, "you can eat me when I'm ready," the thick husk begins to split into four sections once maturity is reached in early fall.  Breaking of the husk happens as the fruit dries out, just before or just after it falls from the tree.  Once the husk splits, the hickory seed, or nut, is no longer safe.  For our purposes here, we will refer to the hickory fruit as a nut.  Which despite what scientists say, still seems to make the most sense.

Some Hickory fruits, or nuts.

In a similar way to the upland oak, the upland hickory begins its life as a nut.  Mother hickories send their progeny off with a simple quick drop from canopy to forest floor.  Once on the ground with the husk split open, hickory nuts don't move much except for maybe a short roll downhill.  Here, the nuts become a coveted food source.  In most years, these predators will quickly find and consume nearly every nut produced by the mother hickory.  However, every few years or so, such an abundance of nuts are produced that there are many left over.  In these years of abundant mast (nut) production predators are overwhelmed but still typically locate nearly all the seeds that fall from the tree.  However, instead of consuming the nuts immediately, certain forest creatures cache the abundance throughout the forest.  Deer, turkey, and bears all immediately eat hickory nuts in hopes of fattening up for winter.  Other predators such as squirrels, chipmunks, Bluejays, and woodpeckers will gather seeds, hiding them in caches throughout the forest and new locations outside of the forest.  These caches of nuts are then to be consumed later in winter when other food sources are scarce.  Woodpeckers will most often cache large amounts of seeds in tree cavities where they will easily be relocated.  Squirrels, jays, and chipmunks will hide seeds by burying them in many caches just below the soil surface, then attempt to relocate them later in the winter.  Amazingly, most of these hidden caches will be relocated and eaten.  A very tiny percentage of nuts actually survive the initial scavenging of forest creatures.  In good mast production years many however, will be lost and never be recovered.  Then, once lost, nuts find themselves in an ideal location, hidden away from predators, protected from the elements, planted and ready for germination.

Blue Jays commonly cache large seeds including the hickory nut.