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TOPIC: Black, scarlet and northern pin (Hill's) oak
http://groups.google.com/group/entstrees/browse_thread/thread/f20b624c9d465bf8?hl=en
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== 1 of 2 ==
Date: Wed, Mar 26 2008 5:22 pm
From: doug bidlack
ENTS,
these three species have interested me for a number of years because
of the great difficulty in telling them
apart from one another. They also happen to all occur in
southeastern Michigan, particularly in Oakland
County where I grew up. Northwestern Indiana / northeastern Illinois
is also supposed to be a great
place to find all three together.
The fairly recent posts by Beth, Lee and Bob have prompted me to add
my two cents worth that I've picked
up over the years. I've been a bit slow to respond because of a new
computer and my attempt to add a link
to some photos of these three species...I sure hope it works!
I'll start with how to tell them apart.
Bark: I can't tell them apart on youngsters, but when they get older
black oak seems to have the thickest,
most deeply furrowed bark. In the classic example of black oak, at
least for me, it is often very blocky in
appearance. Hill's oak (northern pin oak) has thin, shallowly
furrowed bark. It often looks like someone
flattened the ridges into plates by pounding on them. Scarlet
oak bark usually seems to be intermediate
between black and Hill's oak. Oh, from now on I'll refer to northern
pin oak as Hill's oak. I think I
started doing this because the folks at the International Oak
Society seem to prefer this common
name. I don't know why they prefer this name, but I like it because
Hill's oak is more like black and
scarlet oak than pin oak (Q. palustris) and it also is found in dry
soil regions rather than the floodplain
areas where pin oak occurs. I also like the shorter name.
Leaves: Black oak has the largest leaves (10-20cm long) with the
shallowest lobes and Hill's oak has the
smallest leaves (7-13cm long) and perhaps the most deeply lobed.
Scarlet oak is again in the middle, but
much more like Hill's oak (8-15cm long). Black oak leaves turn some
shade of brown in fall while scarlet
oak leaves turn some shade of red in fall. Hill's oak can have
leaves that turn brown, red or anywhere in
between in fall.
Winter buds: Black oaks have the largest terminal buds (6-12mm long)
and they are ovoid to conical and
hoary-tomentose. Hill's oak has the smallest terminal buds (3-5mm
long) and they are 5-angled in cross
section and usually pubescent only toward the apex. Scarlet oaks are
very similar to Hill's oak but the
terminal buds are a little larger (4-7mm long).
Fruit: Black oak acorns are about 1.2 to 1.8cm long and the cup has
loosely fitting scales that form a
slight fringe. Hill's oak acorns are about the same size, but the
cup scales are closely appressed and
they don't form a fringe at the margin. The nuts are also often
ellipsoid in shape and they sometimes have
vertical stripes. Scarlet oak acorns are like Hill's oak acorns
except that they are a little larger (1.3
to 2.2cm long) and the nuts are not ellipsoidal. Scarlet oak acorns
also often have faint concentric
rings near the apex.
Andrew Hipp and Jaime Weber published a paper in the Proceedings of
the Fifth International Oak Conference,
Fall 2006. The title was "Taxonomy of Hill's Oak (Quercus
ellipsoidalis E.J. Hill) in the Chicago
Region: Preliminary Molecular Evidence". They found that
"Scarlet oak, Hill's oak, and black oak can be
distinguished from one another using molecular genetic data"
and that "Hill's oak and scarlet oak are
taxonomically distinct, not simply regional variants of a single,
widespread species". They also found
that "Black oak and Hill's oak are less distinct from one
another than either is from scarlet oak". This is
a little surprising, since Hill's oak appears to be more similar to
scarlet oak morphologically.
Andrew Hipp was the person that really helped me to understand the
best characters for distinguishing
black oak from the other two. Winter buds are definately the best
and the slightly fringed acorn
cups are next best. The difference between scarlet oak and Hill's
oak is more subtle. Scarlet oak has
slightly larger leaves, acorns and winter buds. In addition, the
nuts of Hill's oak are often ellipsoid
and, at least in Oakland County, Michigan, the leaves generally do
not turn bright red (I don't think this
is true for most other regions). Scarlet oak acorns also often have
concentric rings near the apex. One
more character that I didn't mention above is that Hill's oak often
have many persistent dead branches on
the lower trunk.
I have a link to 20 pictures of these three species that I took in
the Kensington Metropark / Milford,
Michigan area.
http://picasaweb.google.com/d.e.bidlack/DryRedOaks
A couple notes about some of these pictures.
Black oak #2 and Hill's oak #1 are a stones throw from one another
and wonderfully easy to separate from one
another (great representatives of their respective species).
Hill's oak #3 is fatter than the Michigan champion for this species,
but I'm not entirely certain that it is
isn't a black oak. The bark is unusually thick and deeply furrowed
for Hill's oak, but then again I've
never seen one so big around! Almost all the oaks in the vicinity
are Hill's oak. I'll have to go back and
check the winter buds and acorns sometime to verify that this is
indeed Hill's oak. As for the current
Michigan champion, it is supposed to be located in Oakland County
but I was unable to locate it last year
in November.
Scarlet oak #2 could be Hill's oak, but the leaves are on the large
side and I've never seen a Hill's oak
with leaves so red in Kensington Metropark. The tree appears to be
too young to be producing acorns yet.
The leaves are a dead ringer for scarlet oak here in southeastern
Massachusetts, but then again I've seen
plenty of pictures of the leaves of Hill's oak in other areas that
might fit those in this picture.
Doug
== 2 of 2 ==
Date: Wed, Mar 26 2008 6:11 pm
From: James Parton
Doug,
There are so many types of oak that I often find some of them hard
to
identify. Quercus is a large genus.
JP
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