In Search of Long Island Rare Plants 1 – Silverweed

From Steve Young – NY Natural Heritage Program

Earlier in June I travelled down to the South Fork of Long Island where, with funding from The Nature Conservancy, I explored various natural areas in search of rare plant populations that have not been seen in 20 years or more. My first stop was a salt marsh on Peconic Bay where I was on the lookout for Silverweed (rare plants should never have weed in their name) Argentina egedii ssp. groenlandica that had been documented in the mid ’80s (this used to be called Potentilla anserina).

The marsh had an extensive ring of Phragmites around it (not mentioned on the form from the ’80s) and I was sure the plants had been overrun by it.

Phragmites around the marsh.

I searched and searched and was on my way out of the marsh when lo and behold there was a small patch of Silverweed hanging on where the Phragmites was not so thick.  Its bright yellow flowers were calling out to say, “I’m still here!”

Its leaves are green on the top and white hairy on the undersides.

In the Napeague area I looked for another old record in the saltmarsh but it was not to be found.  The marsh was beautiful in the late day sun.

The mosquito ditches were evident here as in almost every saltmarsh on Long Island.

One of the uncommon plants of the saltmarsh I saw was saltmarsh arrow-grass, Triglochin maritima with its tall spike of flowers and small tepals. It is the only genus in the Arrow-grass family, Juncaginaceae, a monocot family that has one other species in NY, Triglochin palustre, a rare plant of calcareous fens.

On the dunes surrounding the marsh are plants of pine-barren sandwort, Minuartia caroliniana, an uncommon plant on the Heritage watch list along with two other sandworts, Minuartia groenlandica of the alpine summits and Minuartia glabra of the Shawangunks. Its white showy flowers are hard to miss.

My last stop was a saltmarsh along the northwest side of Napeague Bay to look for a small population of Silverweed that had boats sitting on top of it in 1985. Again, the dreaded Phragmites has moved in and taken over almost all of the marsh except for a few small areas that had yellow thistle. To my surprise I discovered a new population of the rare slender blue flag, Iris prismatica, just hanging on in the same area as the thistle.  One rare plant lost but another gained.  That leaves about seven populations of the Silverweed remaining on Long Island and Fishers Island.

A plant of yellow thistle.

The yellow flower heads with long bracts.

Iris prismatica still stands!

More about the iris in a future post along with searches for white-edge sedge, Carex debilis var. debilis (sedge searches can be fun!) and the two varieties of southern arrowwood, Viburnum dentatum.

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Explore posts in the same categories: Rare Plant Surveys

2 Comments on “In Search of Long Island Rare Plants 1 – Silverweed”

  1. Penni Sharp Says:

    A friend sent me the link to this. We have thriving populations of both silverweed and Iris prismatica on Fishers Island. I’ll have to look for Carex debilis and some of the others. I believe you have been to the island in the past and, of course we would welcome your return visit if you are interested!

    • nyflora Says:

      Actually I have never been to the island but have catalogued many of the rare plants found there by Gordon Tucker. I would love to come out sometime and look at the rare plants but probably not until next summer. Thanks for the invitation!


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