Help Save our Hemlocks!

Posted on January 13, 2023

Hemlocks are large, Christmas tree-like evergreens with gently drooping branches and lots of delicate leaves that provide dense shade. They are native trees that can be found throughout this part of Michigan, and they provide beneficial shade that keeps rivers and streams cool for cold-water fish like salmon and trout, and winter shelter from the elements for deer and other animals. Some people think their leaves when crushed smell similar to the unrelated plant poison hemlock, hence their name (rest assured, the trees are not poisonous).

Unfortunately, our hemlocks are currently under threat from a nasty invasive insect, the Hemlock Woolly Adelgid. Like most invasive species, these tiny but destructive bugs were introduced to Michigan accidentally, in this case on infested nursery stock. They latch onto the base of the hemlock’s needles and feed on the sugars the tree stores there, killing it within the space of a few years.

You can help us stop the woolly adelgid from spreading! If you have hemlocks on your property, winter (AKA right now!) is a great time to examine your trees for infestation. When the insects attach to the needles, they develop a thick, woolly white coat, about the size of a grain of rice—small, but visible. Look for them on the underside of the needles. You can see what to look for in the photo below.

Other things you can do: don’t plant hemlocks in your yard. Woolly adelgids are often transported on nursey stock. Don’t move firewood from one area to another—you may be moving the insects to a new place as well! Don’t walk near hemlock trees. The wooly adelgid might decide to take a ride with you on your clothing (and in their non-woolly form, they are so small you probably won’t see them there). Finally, use the boot brushes installed at the trailhead of all our nature preserves, and many other natural areas, to ensure there are no little hitchhikers on your shoes.

These gnarly bugs have wreaked havoc on the hemlock population in the Appalacian Mountains. Please help us keep them from doing the same here! If you think you have woolly adelgids on your hemlock trees, report it on by clicking REPORT at the top of the page. Or, if you’d like an expert to come out and check your hemlocks, reach out to SWxSW Corner Cooperative Invasive Species Management Area Coordinator Alex Florian at or 269-633-9044.