New Tree Species Discovered in Illinois, by Me! (Sort of)

This is history for this blog.  I have discovered a population of a tree species that theoretically does not exist in Illinois.  I visited Starved Rock State Park in LaSalle County recently.   For those unaware of Starved Rock State Park, it's a series of canyons and bluffs along the Illinois River likely carved by a massive flood many thousands of years ago.  The rolling topography is unusual for Illinois, and reminiscent of the Blue Ridge Mountains that I visited last spring.  The leaves have fallen mostly off the trees.  This makes all the white pines (Pinus strobus), eastern red ceders (Juniperus virginiana), and white cedars (Thuja occidentalis) present very visible. I found something else that looked a lot like a hemlock tree.  However, Tsuga canadensis, the Eastern Hemlock, is not recorded from Illinois since 1962. The record was found on the Illinois State Museum's herbarium website. The Illinois State Museum records are rather hazy and it's unclear whether naturalized trees were used or not.  Conditions change a lot, and it seems that this record of the plant has been lost in the depths of the Illinois State Museum's herbarium.  Tsuga canadensis is not listed as a threatened or endangered species in Illinois, it's just not listed at all according to Illinois Department of Natural Resources or essentially all Illinois wildflower related sites.  For all practical purposes, eastern hemlocks do not grow wild in Illinois.

This picture contains two suspected hemlock trees in the center and on the left.

I took a hike today along St. Louis Canyon in the park. This is a fairly popular trail, with people visiting all year long... and yet, most people seem to only record the waterfall present.  Notable plants in the area include the aforementioned white pine and white cedar, as well as forbs like harebells (Campulana rotundifolia), all of which are rare in Illinois.  Starved Rock also has a third of Illinois' fern species, and I saw at least seven there even after several frosts had already come through.   So it is a very biodiverse area.  The canyon was cool and damp all year round, just the way hemlocks like it.  So seeing about a dozen of them, with a few more growing up in moist crevices along the cliffs, was unsurprising.   I positively identified the plant  with two biology professors as witnesses.  I fully expected to come home and see that eastern hemlocks are a threatened species in Illinois.  It took a full half-hour to find out that they have even been recorded in the state once, albeit 50 years ago.  Below is the Bonap range map of eastern hemlocks.  Note how they come close to Illinois in Indiana and Wisconsin, but never into Illinois.  I have seen hemlocks at Shades and Turkey Run State Parks in Indiana, which contain environments nearly identical to Starved Rock.  (North-facing heavily wooded canyons, cool, damp canyon floors, exposed upland bluffs, large populations of disjunct species, etc.  The differences are actually very minor in climate and ecosystem The four yellow-shaded counties in western Indiana represent the hemlock populations in those two state parks)



Here's an interesting fact,  Canada Yew, Taxus canadensis, is recorded from Starved Rock, and I have never seen it there.  Superficially, at least, Canada yews and hemlocks look fairly similar.  However, Canada yews lack the upright habit of the trees I saw today, and the trees I saw today have needles about half an inch long at the most.  Canada yews have needles roughly an inch long.   Could hemlocks be misidentified as Canada yews?  Possibly.  I suspect Canada yews are also found in Starved Rock, however, as I saw Canada yews for certain in Shades State Park in Indiana and Canada yews are more common in other parts of  northern Illinois as well.

Below are a few other pictures.  I forgot to get a close up, which would have been much more helpful.  The lighting in the canyon was also very bad, so I am unable to present crisp and clear photos.  I feel not unlike a Loch Ness monster photographer, except trees are immobile and easier to locate.

After all this, I have drawn the conclusion that eastern hemlock trees do in fact exist in the wild in Illinois.  A  population grows in St. Louis Canyon, and at least one other hemlock was spotted in Kaskaskia Canyon later on the same day.  Therefore, it is likely that Illinois has a new record, at least, for a tree species, and possibly a new tree species for the state entirely.   I'm extremely excited to be the one to find it.

UPDATE:  It's been over a year since I made this discovery, and I have since learned that the Eastern Hemlocks discussed above are an introduced, nonnative population.