09 January 2021

Flowers and moths in Wisconsin in the winter

I don't hike the arboretum in winter, so the photos here are of our yard after the first heavy snowfall of the year.  But I do get newsletters from the arboretum on a regular basis, and the most recent one included some information that was new to me.
"It has long been believed that fallen pine needles acidify (reduce the pH of) the soil. This isn’t the case, however. While the fresh needles are acidic, the pH is neutralized during decomposition and they have no real effect on soil acidity. A recent study from the University of Wisconsin–River Falls looked at soil pH under older deciduous and coniferous trees, including four pine species, and found no relevant effect on soil pH caused by needle or leaf litter decomposition over time."
"Sporting fragrant, perfect flowers with four unique sulfur-yellow, strap-like petals, common witch-hazel (Hamamelis virginiana), a Wisconsin native, still displayed a few flowers in December. The common name is thought to derive from the old English wych, meaning “to bend,” in reference to the plants flexible branches, and “hazel” comes from the resemblance of the leaves to those of hazels in the genus Corylus.

Witch-haze flowers are fragrant, bear nectar, and produce abundant sticky pollen. They are not able to self-pollinate however, which indicates that they are insect pollinated. Though witch-hazel reproduction is not fully understood, research indicates that flies and fungus gnats play a role in pollinating the flowers in the fall before freezing temperatures. For flowers present during winter, owlet moths in the family Noctuidae, referred to as shivering moths, appear to play a role. These moths overwinter as adults, living under leaf litter, and have the ability to raise the temperature around their flight muscles by as much as 50°F by shivering, so they can fly in search of food during winter months."

You learn something every day.


  1. The pine needle information is interesting and contrary to what I have always believed as well. I wonder why, fewer and different species grow under my blue spruce than a few yards away from it.

    1. I was stunned as well, always having believed that needles acidified the soil. Re the lack of growth under pines, I have noticed that the pines in my yard (cedar and spruce mostly) have shallow and very extensive and aggressive root systems. In the second photo above the pine branches overlie the driveway, and a quarter-inch thick layer of needles accumulated there. When I did some cleanup and shoveled away the needles, I found a dense root mat under the needles ON TOP OF THE CONCRETE. I suppose in the warlike competition for light and water the pines are just exceptionally successful, which may be one reason for your gardening frustrations.

  2. in south coastal new england, witch hazel blooms in february and march. i am not sure how / why your WI WH would still be blooming in december?



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