The Leaves Lingered

Though most trees are bare, the hilltop oaks still have leaves on 30 Nov 2021 (photo by Kate St. John)

4 December 2021

Last weekend many homeowners in Pennsylvania were annoyed that they had to rake leaves after Thanksgiving. A decade ago this would never have happened because the trees were bare by 5 November. Nowadays the leaves linger. Our warmer climate keeps them on the trees.

The delay in leaf drop has been increasing for at least a decade. In 2008-2012 most of the trees were bare by 2 or 4 November. In 2017-2021 the trees waited until 25-30 November. (*)

Meanwhile the height of fall color is later and lackluster. Twenty years ago we used to go leaf peeping on Columbus Day. This year the height of color in Schenley Park was on 13 November and not particularly breathtaking.

Fall color at Westinghouse Memorial in Schenley Park, 13 Nov 2021 (photo by Kate St. John)

Trees need a particular weather combination to trigger fall colors and leaf drop.

The timing and quality of color changes depend on a combination of temperatures, precipitation and sunlight. The best fall color displays occur after sunshine-filled days and cooler nights, following healthy doses of rain in the summer.

Washington Post: Fall foliage flopping: How climate change is dulling and delaying your leaf peeping

But it was way too warm in October. In fact it was the world’s fourth warmest on record.

U.S. Temperature Outlook for October 2021 issued 30 Sep 2021 by National Weather Service

The leaves lingered and finally by 30 November 2021 most of the trees were bare. Note that this date and all dates mentioned above are assessments of this same hillside in Schenley Park.

More than half of the trees are bare, Schenley Park, 25 Nov 2021 (photo by Kate St. John)

Read more about the disappointment of this fall’s foliage — and the economic impact — at the Washington Post: Fall foliage flopping: How climate change is dulling and delaying your leaf peeping.

(photos by Kate St. John, map from the National Weather Service)

4 thoughts on “The Leaves Lingered

  1. We visited Powdermill yesterday afternoon, after I had read this piece. On the ridges, the oak leaves are off. So it appears that there are elevation related temperature differences. I remember in the early 1980’s driving S.R. 51 between Large and Lewis Run Road, and seeing the brilliant orange, yellows and reds of maple tree leaves in October. They still do, but maybe somewhat muted. In the 1960’s, my dad liked to take landscape photos in the fall in WV and MD. The mountains were so brilliantly blanketed with the fall foliage.

    The City of Pittsburgh is a heat island.

    1. Yes, the city is warm and leaves stay on longer here. I forgot to mention in my post (but have added it now) that the leaf-dates are all from observations of the same hillside in Schenley Park, pictured in the article. The news sources (links) say the height of color is now later everywhere.

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