Pioneer Valley Fern Society

A Rare Fern

Cryptogramma stelleri

Randy and I are always looking for the unusual or rare ferns that are supposed to be in our area of western MA. It is very helpful to be able to see one in person somewhere, so we have a better search image out in the field. Our photo here is of Cryptogramma stelleri, or Fragile or Slender Rockbrake. It was shown to us by a friend of a friend, in Vermont. It was exciting to see it in person, and it is so pretty! According to the new edition (2023) of Northeast Ferns by Steve Chadde, it is considered endangered in MA, but is listed as being found (at least once!) in Franklin and Berkshire counties. It is generally found growing on shaded, moist calcareous rock ledges and crevices at higher elevations. These were seen in an abandoned limestone quarry.

They are not evergreen, and usually have dried up by now, but the rainy weather has helped them last a little longer this year. The fronds are dimorphic, and you can see both in this photo. The sterile fronds are shorter and rounder, more like wall rue. The longer thinner fronds in the photo forefront are the fertile ones. The sori or fruit dots are hidden on the underside of the fertile fronds in a rolled edge, called a false indusium. You may have noticed similar structures on the back of the Maidenhair ferns. The Maidenhair ferns are in the same family (Pteridaceae) as these Rockbrakes, and the Purple-stem Cliffbrake (Pellaea atropurpurea) some of you have seen. These three species have a false indusium covering the sori on the back of the fronds.

Needless to say, if you see Cryptogramma stelleri in western MA, we would love to see it too. Most importantly, you should report the occurence to the MA Natural Heritage & Endangered Species Program.

We had a couple cancellations of planned fern walks or talks in July because of the stormy weather. The MACC workshop in Sunderland has been rescheduled for Friday August 18th. We have a free public presentation for the Athol Bird & Nature Club this Sunday August 6th at the Millers River Environmental Center. Check our August calendar of events for details. We will plan a free public fern hike in our area this month too.