Nature Notes: A Month’s Growth (Timelapse of a Leaf)
For this #FloraFriday, witness the miraculous month-long growth spurt of a leaf (yes, one leaf) of a beloved neighbor of the woods, the white ash tree (Fraxinus americana). We start on May 20th, when the large leaf bud has just opened. In the following days, we see many compound leaves start to emerge.
A compound leaf is a trickster; though it looks like a group of leaves, it’s actually one leaf made up of multiple leaflets. For example, as the days go on, we see that this one white ash leaf has seven leaflets. To determine if you’re looking at a leaflet or a leaf, look at where it attaches to the stem; if you find a bud hiding there, you’ve found a leaf. If there’s no bud, you’re looking at a leaflet.
On June 5th, the same day the leaf suffers the indignity of being adorned with a splotch of white bird poop, we see small spots start to appear, especially on the terminal (ending) leaflet. In a matter of days, they’ve swollen to their full size. We suspect it’s the work of the ash bullet gall midge (Dasineura pellex), which according to Pete Woods, an ecologist for the Pennsylvania Natural Heritage Program (PNHP), “lays its eggs in ash leaves, and the eggs and larvae coax the leaf into growing galls that both feed and protect the larvae until they mature.” Though it causes unsightly bumps, the insect doesn’t damage the overall health of the tree.
The same can’t be said for the emerald ash borer (Agrilus planipennis), an invasive beetle originally from Asia that arrived here likely on cargo twenty or more years ago. Since then, it has killed hundreds of millions of ash trees in North America, including some here in Vermont. The female beetles lay their eggs in the cracks and crevices of the tree’s bark, and once hatched, the new larvae burrow into the tree and feed on the inner bark, disrupting its ability to transport water and nutrients. Infected trees die within ten years.
As sad as it’d be to lose ash trees, we’d also lose all of the invertebrates that depend on ash trees for their survival; according to Pete Woods, there are more than 98 such species in North America. Among those is the aforementioned ash bullet gall midge and the great ash sphinx (Sphinx chersis), a large moth that Woods calls the “nocturnal equivalent of hummingbirds,” because of their tendency to hover in front of flowers while sipping the nectar.
As we root for the scientists working to save the ash trees, we remind ourselves to take the time to pause, to say hello, and to get to know them, our longstanding neighbors, while they’re still here.