Trees of Henderson part 1: the Mighty OaksI am beginning a series of articles about the many grand trees that are
native to the Minnesota River Valley near Henderson. Henderson is known for
its bird watching, and I'd like to let people know about the diversity of
trees as well. Maybe we could promote "tree watching" in the area, and I'm
sure those birders might like to know more about the many trees that provide
cover, nesting habitat, and food for our feathered friends.
Situated in the Minnesota River basin, and harboring some of the richest
soils in the world, the Henderson area is so dense with trees at times it
feels like a jungle (especially with the mosquitoes this year). I have
chosen the oaks to kick off my series of essays about trees, as they are one
of the dominant tree groups around here, and recognizable by most. I'd like
to share with you some of the natural features and uses by humans of the
trees we love to see grow and flourish every year.
One can find 6 species of Oaks in the area, although only two are common
enough to be seen regularly. Oaks are generally divided into two
categories, the red oaks and the white oaks. These two groups are very
quickly defined by the lobes of their leaves: red oaks have sharply-tipped
lobes, while the white oaks have rounded or smooth lobes.
White Oak branch and leaves - note the scaly bark and evenly lobed leaves. 
Bur Oak Leaves.The white oaks are represented by three species around here, the Bur Oak
(
Quercus macrocarpa), the White Oak (
Quercus alba), and the Swamp White Oak
(
Quercus bicolor). By far, the bur oak is the most common. In fact, what
most people call "white oak" around here is actually the Bur Oak. If you've
ever picked up an acorn in the fall with a fuzzy cap (looks like many stiff
hairs growing from the cap), you've found the seeds of a bur oak. They are
found on the bluffs and in meadows, and prefer well-drained soils. They
make great shade trees because of their wide crown and long horizontal
branches.
A very large Bur Oak tree in a meadow.The shape of the Bur Oak varies greatly depending on their habitat, from a
tall skinny tree in deep woods to a shorter but very wide tree on the open
meadow. Their bark is very rough and furrowed, and sometimes looks smooth
and whitish close to the ground where a fungus has destroyed the outer layer
of bark. This does not kill the tree, and makes it a little easier to
distinguish it from other white oaks.
A rare native White Oak.The White Oak and Swamp White Oak are sparse around here, but I suspect the
White Oak used to be more common before it was lumbered due to its
incredibly valuable wood. There are slight differences in the leaves and
bark, but the best way to distinguish the white oak from the Bur Oak is the
lack of the fuzzy acorn caps. The only pre-settlement White Oak I have
found around here is in a big woods remnant patch at the Ney Nature Center,
but I know there are more. Large Bur Oaks can be found almost anywhere
trees grow, in the city or county parks, and surrounding of hilltop school,
the ball field, bus garage, and housing developments.
White Oak lumber has been prized for centuries for cabinets and furniture,
ship-building (such as the USS Constitution), barrel-making, structural
timbers, and fence posts. It has a natural ability to resist rot, decay,
and insects, hence the whiskey barrels and ships. I have restored a number
of old hand-hewn log homes in the area, and in every case the sill log
(makes contact with the ground or foundation) is of White Oak. Same goes
for the sill beams in barns and houses, and floor joists or timbers in old
outbuildings. Anywhere the wood was going to be in contact with moisture
regularly, White Oak was used. It was the "treated lumber" of yesteryear,
due to its cellular structure in cross-section.
If anyone has an antique piece of furniture that features "quarter sawn" or
"tiger-striping" veneer, that's White Oak too. It far exceeds other native
hardwoods in structural strength, and stays straight under the years of use
in an old barn. The true White Oak is an amazing lumber tree, and like I
said before, that's probably why we don't see it around here anymore. The
Bur Oak is a good substitute, but it's hard to find a straight length of it,
and its knots, twists, and burls make it commercially undesirable. However,
if you have an old oak fence on your farm, it's probably Bur Oak, and has
probably been there for many many years. I know of no better firewood
around here than Bur Oak.
On to the Red Oak group. You will find Northern Red Oak (
Quercus rubra)
nearly everywhere you go around Henderson, and Northern Pin Oak (Quercus
ellipsoidalis) can be seen often. Black Oak (
Quercus velutina) might make
its rare appearance in the river valley, but is mostly limited to extreme
southeastern MN. Go up to Allanson's park in Henderson and you will see
some of the largest Red Oak trees in the area.
A stand of Red Oaks deep in the woods.Both the Red Oak and Pin Oak (also known as Jack Oak) grow straight and tall
and their leaves have sharply tipped lobes. Their leaves are a waxy dark
green, and by autumn they turn a range from brown to orange to a deep
scarlet, offering the fall colors on a hillside a splash of red. By
comparison, the Bur Oak must be too modest for showy colors and goes
straight from green to a crispy dry brown in the fall.
The red oak group often keeps their brown leaves on all winter long, making
them easy to identify after the leaves are gone. The Red Oak and Pin Oak
are sometimes difficult to differentiate, but the pin oak has waxier leaves,
deeper lobes, needs a lot of sunlight, and is a smaller tree. The Red Oak
grows in deeper woods and can grow to be a very large tree. There are many
subtle differences between the two, and I would suggest consulting a good
tree book or knowledgeable person if you find a mystery red oak. The lumber
from these trees is virtually the same, and is probably not sorted when
loggers send it to the mill.
Northern Red Oak leaves - sharp tips, more common than pin oak. 
Northern Pin Oak Leaves - note the waxy surface and deeper lobes.Red Oak is one of the most commonly lumbered trees in the U.S., and your oak
kitchen cabinets and oak hardwood floors are almost certainly Red Oak. It
does not offer the quality of rot-resistance, because the cut ends of the
logs have tiny straw-like cells that actually suck up moisture, rather than
resisting it as in the White Oak. However, its straight grain, freedom from
lumber defects, stability, and color make it ideal for woodworking.
Red Oak splits very cleanly, and was used by settlers for rail fences and
roofing shakes (before Western Red Cedar came from the Rockies on the rail
road). Does anyone have an old froe lying around in the barn or tool shed?
This bladed tool was used along with a mallet to do the final splitting
after a beetle and gluts (older wooden versions of a steel maul and
splitting wedge) did most of the work. I've heard from some old-timers that
if you char the end of a red oak post, it will last just as long in the
ground as White Oak. It is fine for above-ground use in buildings, and if
allowed the chance to stay dry, will last indefinitely.
The Red Oak's acorns are abundant, large, and smooth. I know that good
flour can be ground from its acorns, and made into bread for those who like
wild edibles. The acorns are also a very important food source for local
squirrels, turkeys, and deer, carrying them through the deepest winters.
In the next couple of months I will talk about the Elms, Poplars, Maples,
Ash, Cherries, Willows, Birch, Ironwood, and more of the countless small
trees and shrubs that make up the density of our woodlands, ravines, and
bottoms in this Henderson jungle. I will try to write more often than
bi-monthly, I think this tree series may take a while.
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