Botany Detectives: Exploring the Nantucket Flora in the Off-Season

Since arriving on Nantucket in January of 2008, I’ve found that the colder months offer some of the best opportunities to check out new places and get the lay of the land. With the summer tangle of scrub oak, grape and other greenery magically absent after leaf drop, you can see a lot more detail. You don’t have to wait for spring to learn about the island’s forests and shrublands!

It’s also a good time to be a botany detective, if you’re willing to sharpen your eye and learn to identify plants by their twigs, buds, bark, and fruit. Check out the paper birch at left, that I noticed while driving down Milestone road. This tree is hidden under entangling poison ivy and screened by scrub oak in the summer, but has recently grown large enough that its outer bark has split to reveal the light colored under layers. That papery bark makes it stand out from all the other vegetation. I stopped to check it out thinking that it might be a grey birch (Betula populifolia), but was surprised to find a paper birch instead! It’s the first I’ve seen on Nantucket.

Some trees and shrubs are easier to key in on that way, giving you a chance to notice the uncommon species of the Nantucket flora. A flora is a list of plants that “belong to” a given place (whether it’s a county, island, state, or region). By “belong to,” I mean that they are able to reproduce on their own without cultivation, but are not necessarily native. For instance, sweet corn can grow here, but you won’t find wild patches of it to harvest out in the Middle Moors–it requires that humans plant the seed each year and coddle it with fertilizer and water. Some other non-native garden plants can escape and colonize new places on their own, such as Oriental bittersweet (Celastrus orbiculatus) and Morrow’s bush honeysuckle (Lonicera morrowii). While they will never be Nantucket natives, these newcomers are now part of the island flora. The more aggressive and commonly planted a species is, the more likely it will become a long-term resident, as long as the climate and soils are suitable.

Updating the Nantucket Flora

The most recent Nantucket plant list, The Vascular and Non-Vascular Flora of Nantucket, Tuckernuck, and Muskeget Islands, was published in 1996 by Sorrie and Dunwiddie. It included 1,265 vascular plant taxa (counting all of the individual species, subspecies, and varieties) as well as 99 bryophytes (mosses and liverworts) and 99 lichens. Along with that list, it described the plant communities of the island and included comments on plants that had once been present, but had not been seen in a long time. You can read a summary of the 1996 Nantucket Flora project here.

Since 1996, island botanists and conservationists have been using this plant list for our work, and we’ve been making notes when new species have been found, or those long-lost to history have been rediscovered. During that time frame, botanists have also made a lot of changes in species’ names and moved many species to different genera or families. Some plants look alike, but are actually not closely related at all. DNA evidence has helped us better understand this complex family tree and has re-shaped some of the branches. Here’s an example of a phylogenetic tree of plants showing some of these relationships:

After years of exploring and making notes about interesting plant finds on the island, last year a group of us joined forces to create an updated Nantucket Flora. Island scientists Sarah Treanor Bois of the Linda Loring Nature Foundation, Andrew Mckenna-Foster of the Maria Mitchell Association, and Kelly Omand of Nantucket Conservation Foundation teamed up with Bryan Connolly, the former Massachusetts State Botanist, now teaching at Framingham State University. The Nantucket Biodiversity Initiative (NBI) provided some grant funding for this project and it will take place over the next few years. When completed, the revised flora will give island researchers an up-to-date resource.

Field Work in the Off-season

Working on this project has given us an added incentive to get out and do some winter and spring botany detective work. Here are some of the trees and shrubs that we have found (or are interested in finding). Maybe you can help. Take a look at some of our finds:

One newcomer that had not been recorded in the Nantucket Flora until this fall was Amur cork tree (Phellodendron amurense), pictured above. We learned about this tree when it was reported by a curious NBI Conference attendee back in November. It was hard to determine what this strange tree with the huge fruits could be from a picture posted on Facebook, but checking it out in person provided several clues to its identity, and the mystery was soon solved. The large heavy fruits of this Asian tree species are noticeable in the winter, and so is the corky bark that thickens and splits as the trees age. But what clinched the identification was the bright yellow inner bark and the citrus scent of both the crushed fruit and the peeled bark. You may have noticed these “weird trees” yourself while driving by Sesachacha Pond. We’d like to know if there are more growing wild on the island. These looked like they were planted a long time ago, since they weren’t growing in a landscaped yard.

Another “new” species for the island that’s easy to spot in winter is bristly locust (Robinia hispida), a shrub in the legume or bean family. This shrub was spotted along the Polpis bike path near a section of former state forest land (now owned by the Land Bank). It’s native to the Southeastern U.S., but has been introduced in many other parts of North America — including Nantucket, apparently. The pods look like spiny edamame, but the bristles on them and on the stems are soft. Have you seen this bush growing in your neighborhood?

Some other notable recent “rediscoveries” have been made, such as an ancient grove of witch hazel (Hamamelis virginiana) at Coskata Woods that was reported by Thad Jones in 2014. Witch hazel is a common shrub on the mainland, but was only reported once on Nantucket: near Sconset Dump in 1896. This is another good species to look for in fall and winter because its yellow flowers open in late fall, and it has distinctive seed capsules that last through the winter and disperse their seeds the following year. Where else may this sneaky shrub be hiding on Nantucket? If you are passing through a tangled swamp in a forested area, you might be the next person to locate an unknown patch of this species growing wild on the island.

Some other tree and shrub species that might be easy to spot in winter — and that we would like to relocate on island — are speckled alder (Alnus incana) once found at Capaum Pond, and musclewood or American hornbeam (Carpinus caroliniana), which was reported as “rare and shrublike” by Bicknell, but without a location or pressed specimen, back in 1901.

If you are out and about this winter, keep an eye out for unusual plants hiding in plain sight, and let us know if you find something interesting!