This is a tale of a dying 100-year-old white ash (top rear, nearly leafless branches) and five opportunistic Norway maples (foreground, leafy green) located near a stone bridge over the Bronx River Parkway in Yonkers. Here’s a view from the interior:
Some of you may know the ash as the preferred wood of the Louisville Slugger – the once predominant bat of major leaguers and little leaguers alike. (I had a favorite Mickey Mantle Slugger that I used to hit my one and only homerun when I played the game.)
Ash Trees under Attack
Sadly, ash trees have been struck by a pestilence – the emerald borer beetle (EBB), a small metallic-green bug, that attacks ash trees’ life-support systems from the inside out. Adult beetles lay eggs in the bark’s crevices. When the larvae hatch, they bore into the tree’s inner living tissue that carries water and nutrients between the roots and the leaves. The larvae carve extensive serpentine tunnels that eventually destroy the tree’s circulatory system and starve it to death.
In only a year or two, the tree’s crown begins to thin, the bark splits, and new shoots sprout from the trunk as it struggles to survive. By the time the distinctive D-shaped exit holes of the adult beetles appear, it’s too late. Trees typically die within two to four years of infestation. Like the American chestnut and elm that came before it, the days of a healthy ash population in our forests and parks are over.
(The EBB is an invasive insect species native to Asia that was most likely introduced into North America in the early 2000s. The EBB is non-lethal to the ash trees in its native habitat because as those trees evolved, they developed natural defenses that limit the beetle’s damage, and there are also native wasps that prey on and control EBB populations.)
Invasive Maples are Bullies
Norway Maples, on the other hand, are thriving, but are no substitute for native trees like the ash, which support the health of the ecosystem. These maples are invasive bullies that cause harm.
Unlike our red, silver and sugar maples, Norways, as the name suggests, came from Europe. Introduced in the 1700s, they thrive in urban environments and were widely planted on city and suburban streets. However, in the forest, the Norway’s dense canopy casts deep shade, preventing sunlight from reaching understory plants and seedlings of native trees. Additionally, its shallow, extensive root system monopolizes water and nutrients, making it difficult for other vegetation to establish nearby.
The Norway maple has a distinct advantage over native trees because it grows quickly and has a longer growing season than native trees. Its leaves develop early in spring before the native trees and remain greener longer. This gives it a competitive advantage in the all-important battle for the sun.
Once established, Norway maples form monocultures that reduce plant diversity and alter soil chemistry, weakening native habitats and the wildlife that depend on them. It has been reported that Norways support less than 10 species of native insects, when native maples host many hundreds.
If you aren’t sure what kind of maple is growing in your neighborhood, pick a leaf and look at the sap flowing from the stem. If it runs milky white, it’s a Norway.
When I was growing up, I used to look forward to the Norway maple seeds helicoptering down to the sidewalk each summer. I loved to peel the ends apart and stick them on my nose. We called them Polly noses. Today I’m less enthused.
For three years I’ve watched the 100-year-old ash tree succumb to the borer beetles as the Norway maples prospered. It’s a shame. Soon, the Westchester County Parks Department will need to remove the dead ash before it becomes a hazard and starts to drop its limbs on the Parkway. The miserable maples will simply take its place in total victory.
This story is the fourth in a bimonthly series about trees in Yonkers. If any reader knows of a particular tree that they feel is worthy of an exposé, please contact me through the Yonkers Ledger at phil.zisman@theyonkersledger.com
