Frosty Facts
It’s the best time of the week: time for the phenology show! KAXE-KBXE staff phenologist John Latimer is pondering the changing weather. After last week’s plus-85-degree days, temperatures dropped to 29 degrees on Oct. 9. Temperatures under 30 degrees are considered a “hard” or “killing frost,” while temps in the 30-32 degree range are “light frosts”.
Typically, the first frost of the fall occurs around Sept. 19, and the first killing frost around Oct. 6. (In a year like this one, when the first frost is also a killing frost, both dates are the same.)
The latest hard/killing frosts in John’s 40-records are:
- Oct. 9: 2023, 1986
- Oct. 11: 1992
- Oct. 15: 1997
- Oct. 18: 2010
- Oct 19: 2013
- Oct. 20: 2016
- Oct. 21: 2021
- Oct. 24: 2019
You’ll notice that 55% of the latest first hard frosts on record were in the last decade: a sign that these hard frosts have occurred later in the year over the last 40 years. (If there had been no change, we would expect each decade to have about 25% of the latest first frosts.)
John also keeps separate records on the first frost, whether it’s a killing frost or not, and the last frost of spring. Never fear: we’re running the numbers on John’s datasets and you’ll hear more soon!
There doesn’t appear to be any relationship between the arrival of the first frost and the severity of the winter. 2022, for instance, had a very average first hard frost date (Oct. 6), but a stupendously cold and snowy winter, with snow depths at record-breaking levels in Duluth and the Twin Cities.
John is hoping that the El Niño effect will spare us from another cold and snowy winter: the last two years were both El Niñas.
Plant progression:
- Bare trees/shrubs: American hazel, beaked hazel, red maple, bur oak
- Peak color: red oaks (bronze)
- Still green: Buckthorn, northern holly, birches, aspens, willows, maidenhair fern, bristly club moss, running club moss, American yew
- Fruiting/releasing seed: Speckled alder (aka tag alder), birches (will drop seeds throughout the winter- look for them on top of new snow!)
- Flowering: Black-eyed Susan, hoary alyssum, common mullein, evenging primrose (but the hard frost likely ended the flowering)
Species spotlight:
With the hazel brush mostly bare, the forest understory is much less dense. (This is a boon for grouse hunters, who can spot their prey from further away!). However, there are still a few plants that have retained their leaves:
- Buckthorn: An invasive species, this plant holds its leaves long after many of the native plants have dropped theirs. Look for the blue-black berries, football-shaped leaves, and silver-brown bark with a metatllic sheen.
- Northern holly (aka winterberry): The red berries on these shrubs are disappearing as birds stop by for a meal. The holly bushes near John’s house have been completely cleared of berries already. To identify the winterberry, look for dark-colored bark with a chalky white coating on the tips of the branches. Another distinctive feature is that it often forms many stems at the base of the plant.
- Speckled alder (aka tag alder): These plants are close to being bare, but still have a few (John approximates 25% of the leaves remain). The key to spotting this plant is that it creates small structures that resemble pinecones- but it’s not a conifer! These little pinecone lookalikes are ripening, and will soon open to drop the seeds.
- Birches: A birch tree doesn’t look yellow until the very end of the fall. This is because it drops yellow leaves quite quickly after they turn, and the leaves don’t all change color at once: So, instead of looking more and more yellow as the season goes by, the tree just looks more and more bare. It’s only when the last 10% of the leaves remain that the tree will look yellow.
- Aspens and willows: These are the last species to lose their leaves in the fall. Aspen leaves will begin to look flecked with spots of brown or yellow, then turn completely yellow as they senesce.
- Other: Of course, other species vary in their habits and responses as much as we do. Even though peak color for the red maples was a few weeks ago now, there are still a few outlier trees in John’s yard that remain stubbornly green. In nature as in humans, there are a few weirdos in every bunch!
- Evergreens: The club mosses, which are evergreen, are a wonderful sight in the fall forest. Their green is mirrored in the American yew, which John found while on vacation at the North Shore. This plant is a favorite of deer, so it is often only found where deer are excluded or refuse to go. John found such a spot at the top of a rocky knoll!
Bird report
Large flocks of American robins are moving through the area, as well as a few remaining flickers and a few small groups of Eastern Bluebirds.
While on a walk in the woods, John flushed a ruffed grouse out of a tree. As he was recovering from the surprise (grouse are loud when they suddenly FLAPFLAPFLAP away from you!), he spotted another grouse just a few feet away! This one was a large, red-morph male that had its ruff and tail extended. It had clearly been putting on a show for the lady, which John and his dog Mila had so rudely interrupted.
After a moment’s consideration, the grouse decided that John was not an adequate replacement for his Lady of Interest, and he tucked tail (and ruff) and ran off. John, bereft, was left alone still scrambling for his camera.
Don’t you go adopting the grouse’s ways, though! Stick around and enjoy some more phenology while you’re here. (No dancing required.)
That does it for this week! For more phenology, subscribe to our Season Watch Newsletter or visit the Season Watch Facebook page.
Funding for this project was provided by the Minnesota Environment and Natural Resources Trust Fund as recommended by the Legislative-Citizen Commission on Minnesota Resources (LCCMR)
