Seen This Week

Bluets, Knob Hill Community Park, 14 April 2023 (photo by Kate St. John)

15 April 2023

More flowers bloomed and more trees leafed out as hot summer weather continued this week.

I saw a few bluets (Houstonia) and spring beauty (Claytonia) at Knob Hill Community Park yesterday.

Spring beauty, Knob Hill Community Park, 14 April 2023 (photo by Kate St. John)

In Frick Park on Thursday this box elder (Acer negundo) was blooming and leafing out at the same time.

Box elder flowers and leafout, Frick Park, 13 April 2023 (photo by Kate St. John)

But many native trees still looked bare, such as the oaks on this hillside.

Progress of leafout at Frick Park, 13 April 2023 (photo by Kate St. John)

The slowness of native trees made last weekend the perfect time to see the invasive extent of Callery pears (Pyrus calleryana). Native white-flowering trees, such as serviceberry and wild cherry, were not blooming yet so the only white trees in the landscape were the Callery pears.

On 8 April at the Ridge Road interchange on the Parkway West (I-376) I found thick stands of Callery pears as far as the eye could see (first 2 slides below). The trees gained a foothold in disturbed soil after construction of the Ridge Road interchange in 2006 and Settlers Ridge shopping center in 2009. The third slide shows Callery pears in the woods at Wingfield Pines.

Callery pears were banned in PA in 2021. As you can see, we “locked the barn door after the horse got out.”

p.s. This weekend the downy serviceberries are blooming (white) and the Callery pears are growing leaves (white+green) so it’s no longer possible to pinpoint the invasive species.

(photos by Kate St. John)

2 thoughts on “Seen This Week

  1. Great information! I did not know the name of the Callery pear trees, when seeing them as the first bloomers along the parkway west, moving out into Beaver County. How and why are they invasive? We tried to determine how they were placed in such inaccessible spots. Had they existed there before they began blooming?

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