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Stiltgrass, Swallowtails & Sweet Coltsfoot, Oh My!

A field season filled with invasive species and their complex relationships with biodiversity.

Every year there are new species are added to our long list of invasive plants and animals. These range from very hungry caterpillars defoliating trees to water chestnut overtaking our waterways. While this can leave a sense of gloom and doom for the future, our natural areas can also be a source of wonder when you look beyond the surface. Through an internship this summer, I explored the complex nature of our environment: a mix of common and rare native plants, non-native plants, and invasive pests - and the complicated relationships between them.

Native plant finds from Summer 2023, left to right: American spikenard (Aralia racemosa), cardinal flower (Lobelia cardinalis), and gamma grass (Tripsacum dactyloides) - Erin Norton

This summer I had an internship through the New York State Department of Environmental Conservation surveying for invasive species in Steuben and Allegany counties. The goal was to fill data gaps in these areas in the iMapInvasives database, and to better understand the distribution and potential impacts of invasives in the Southern Tier. I took a holistic approach, mapping under-reported common invasive species, emerging and early detection species, forest health issues, as well as rare native plant species.

I have always had an appreciation for knowing more about the species where I live, but I gained a new understanding this summer through numerous field surveys. I hope you enjoy this overview of my survey experiences and are inspired to explore and document the species in your area too!

Forest Health Surveys:

Elm leaf damaged by elm zigzag sawfly - Erin Norton, Summer 2023

Through my forest health surveys I was also able to better understand and appreciate the trees that makeup our forests. Elm species have long been declining due to several factors including Dutch Elm Disease. Recently, the Elm Zig Zag Sawfly (EZS) has begun spreading through the state defoliating the leaves of elm trees. I went to elm stands in Steuben and Allegany to check for EZS by looking for the signature zigzags munched out of the leaves.

I found the insects themselves were often were hiding in the zig zag patterns. The first survey I did, I did not notice until looking at my photos afterward that the larvae had photo bombed (the little guy was hiding on the side of the leaf!).

Beech leaf showing signs of Beech Leaf Disease - Erin Norton, Summer 2023

The other main forest health issue I examined was Beech Leaf Disease, which is caused by a non-native nematode. The telltale sign is the appearance of dark bands in between the leaf veins. We still don’t know exactly how it spreads, but it is on the rise in New York. Similar to EZS, this is just one of many issues already attacking these trees, adding to existing stress.

I often found larger trees with Beech Bark Disease, too, setting these trees over the edge. Beech is one of the main native plants that likes to grow in the understory, meaning its absence would mark a huge change in New York forests.

Some other examples of forest health issues I sampled were oak wilt and white pine decline.

Aquatic Surveys:

Native aquatic plant findings from rake toss surveys - Erin Norton, Summer 2023

Aquatic surveys were among the other cool surveys I did this summer. It’s important that we understand not just what is happening on land, but in the water too; they both impact one another. I performed rake tosses to see what aquatic plants lived in a waterbody. This involves throwing a rake attached to a rope into the water, and pulling it back along the pond bed. I also kept an eye out for health hazards like harmful blue-green algae.

One of the ways I learned about aquatic surveys was through my local PRISM, Finger Lakes PRISM, which has a volunteer macrophyte survey program. I hope this encourages you to check out your local organizations and see what volunteer programs they have, too!

What else is hiding in the woods?

With such enormous issue like invasive species and climate change, it may seem hopeless sometimes. However, there is so much more than just invasive species in the woods, and our native biodiversity is resilient! While I was doing my surveys, I came across many native plants worth documenting too, using platforms like iNaturalist. How can we conserve the native species in a forest without knowing what is there first?

Part of what makes Steuben and Allegany counties special is they are at the edge of ranges for many northern species as well as mid-Atlantic and southeastern species. Along my hikes I came across plants like Sassafras, with their mitten shaped and lemon scented leaves, and the native plants photographed at the beginning of this blog

One of the other surprises for me was how much pollinators seem to love invasives. Butterflies like swallowtails were constantly getting nectar from plants like autumn olive (Eleagnus umbellata) and honeysuckle (Lonicera spp.). Sadly, this does mean less opportunities for native species pollen to be dispersed.

Wild hydrangea (Hydrangea arborescens, rare), Sweet Coltsfoot (Petastites frigidus var. palmatus, rare), and a native swallowtail butterfly drinking nectar from invasive Autumn Olive (Eleagnus umbellata)

I also searched for two rare plants this summer, the endangered sweet coltsfoot (Petastites frigidus var. palmatus), and threatened wild hydrangea (Hydrangea arborescens). This was a very exciting experience for me to get a taste of the unique biodiversity my home state has to offer.

Finding the wild hydrangea was challenging at first, since it likes to grow in steep rocky areas. I had to look straight up a slope to notice the hydrangea, growing on a steep incline at the roadside edge of a forest. I soon realized that the hydrangea population I found was living right alongside invasives like knotweed (Reynoutria spp.) and Japanese stilt grass (Microstegium vimineum), which could threaten the hydrangea in the future.

The sweet coltsfoot proved to be even more challenging - I surveyed a natural area where it was last observed in 1996; one of only three locations in New York where the plant has been documented in the past few decades. When I first got to the edge of the creek where it was last seen, it seemed that this rare plant may not have persisted.

However, I was determined to find it, and so I continued up the creek to expand my search. Since the plant likes to grow in wet areas, I figured it wouldn’t hurt to check the surrounding wetland area. About 15 minutes later, I noticed an unusual looking leaf which I thought might belong the very plant I was looking for. I had some reference photos on hand, but it was still difficult to tell so I took several clear photos.

Once I noticed the first, I realized there were quite a few of these peculiar plants in the area, mixed in with native plants like marsh violet and lesser purple fringed orchid. I also looked for invasive species in the vicinity, but fortunately I only found native ones! Afterward, I reported my finding and the NYNHP botanist was able to verify the sweet coltsfoot from my photo, meaning we now have the first documentation of this species in the past 20 years for the state!

How can you help?

We can always use more trained eyes on the ground! Check out the links below for resources on invasive, native, and rare species.


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