Phenology Report, October 18th 2022
This week begins John's 40th year on the radio! He starts with the fall colors. Thanks to a great growing season, we've had an incredibly red fall: the plants were able to produce lots of sugar and have energy left over to create the chemical compounds that turn the leaves red (and discourage predators). At this time of year, the red color starts to fade to bronze (particularly in the red oak group, which includes the Red Oak and the Northern Pin Oak).
The Pin Oak tends to be redder than the Red Oak, though individual variations exist. The younger trees tend to have more coloration. To help identify them, remember that trees in the red oak group have sharp points at the end of the leaf lobes. Then, look at the lobe depth; if the lobes cut almost to the center line of the leaf, it's a Northern Pin Oak. If the lobes aren't quite as deep (but the lobe points are evident), it's a Red Oak. White and Bur oaks, in contrast, have no points at the end of the lobes and tend to turn yellow instead of red.
Another red plant is the American Hazel (its cousin, the Beaked Hazel, turns yellow). The American Hazel in John's yard turned a deep red this fall and is still clinging to 75% of its leaves: most other hazels have already dropped their leaves. On average, hazels drop their leaves during the first week of October, so they are running a little late this year.
As the American Hazels drop their leaves, they reveal another shrub with deep red leaves. Downy Arrowwood holds its leaves longer than the American Hazel, and in the early season, it's easy to write off the red-leafed shrub as another American Hazel. Once the hazels drop their leaves, the Downy Arrowwood stands out. You can confirm your identification by looking at the leaves: Downy Arrowwood leaves are sharply toothed and feel soft (or downy!).
Asparagus plants are turning bright yellow; it's a perfect time to mark your patches of asparagus, so you know where to look for them in the spring! John uses a little flag in the ground or some flagging tape in a tree to mark his.
Just a few of John's Red Maples still have leaves. Those that do are green and yellow, without as much red coloration. The Norway and White Pine trees have dropped most of their 3-year-old needles, so they look fresh without that reddish-brown color in their branches.
Most of John's Trembling Aspens have dropped their leaves, though one remnant still has about 50% leaf cover. Bigtooth Aspens hold their leaves a week longer than Trembling Aspens and tend to be a more vibrant yellow. (Interestingly, Bigtooth Aspens also leaf out considerably later than Trembling Aspens!) As with all things in nature, there is plenty of variation: John observes one clonal group of Trembling Aspen that leafs out late each year (and drops its leaves late, too!). So, if you notice a tree near you that holds its leaves longer than its neighbors, make a note of it! It may leaf out later in the spring, as well.
One of John's Trembling Aspens hosts an eagle nest, so he tracks it carefully. His records for when it turns over 50% yellow are as follows: October 13th (2014), October 19th (2015), October 9th (2016), October 15th (2017), October 15th (2018), October 19th (2019), 9th (2020), and 24th (2021).
This time of year, many reptiles, birds, and mammals are seen for the last time before hunkering down for hibernation or migrating out of the area. John points out that you need to write down when you see these creatures: for instance, if you see a toad in your yard this week, make a note of it! If you're in the habit, you'll be able to look back at your notes and determine when you saw your last one. Keep an eye out for the season's last chipmunk, robin, and flicker! "Firsts" are a little easier to track since you only have to note them when they appear. Keep an eye out for Fox Sparrows, Tree Sparrows, and Black-eyed Juncos.
John's last note is on the plants that are still stubbornly green. Most of these are non-natives and developed phenological adaptations from regions far away from Minnesota. The triggers that prompt them to lose their leaves differ from our native plants. Some examples include lilacs (which never change color but fall off the plant still green), 'tree' willows such as the weeping and black willow, and buckthorn. Buckthorn is a particularly unwanted invasive, as it shades out many of our most desirable understory plants- think of your favorite spring ephemerals! Luckily, you can quickly identify buckthorn this time of year since their green leaves stick out in otherwise bare forests. To confirm your identification, look for their 'sub-opposite' leaves. The leaves on the left will be just a touch lower or higher than those on the right: not mirrored across the stem, but not widely separated either.
Additionally, cottonwood trees aren't native to Northern Minnesota and hold their leaves late into the fall. River Birches are also introduced, often brought in as ornamentals: they keep their leaves far longer than the native paper birch. To distinguish the two birches, remember that paper birches are a crisp, clean white with pale pink to orange underbark that comes away in scrolls. River birches have much darker bark that peels in scabby patches.
For more phenology, subscribe to our Season Watch Newsletter!