May 17, 1952 & 2002: (re)collected on this day

Both of these specimens were collected on May 17 in Highland Park– but 50 years apart. John Bright collected the specimen on the left in 1952.  Fifty years later to the day, Bonnie Isaac unknowingly recollected the same species in the same location! 
 
If you look closely, you’ll notice the 1952 specimen did not yet produce seed by mid-May, while the 2002 specimen has already started developing the characteristic maple-like seeds.  Due to increasing spring temperatures in recent decades, many plants tend to flower earlier, as shown through herbarium specimens. Botanists at the museum are studying the impacts of human-caused environmental changes over the past century by following in the footsteps of past collectors.  We are revisiting field sites on the same day to compare modern day plants to specimens collected over 100 years ago.
 
Sycamore maple (Acer pseudoplatanus) is a common forest tree in Europe, where they simply call it “sycamore” but should not be confused with our native and introduced sycamores.  Sycamore maple has been intentionally introduced across temperate regions, including the US and New Zealand.  It has since become invasive, meaning it actively spreads across the landscape and can cause ecological damage. It is less common than other invasive maples (such as Norway maple) in this region, but is invasive in several sites in the Pittsburgh area.