The Carlisle Mosquito Online

Friday, December 3, 2004


Sensitive Fern

(Photo by Kay Fairweather)

Name: Onoclea sensibilis or Sensitive Fern, a.k.a. Bead Fern. The genus name is made up of the Greek words onos meaning a vessel and kleio meaning to close, and refers to the tightly rolled fertile fronds. The species name, sensibilis, is Latin for sensitive and refers to the fact that the green leafy sterile fronds die back quickly with the first frost.

When and where seen: Can be seen all around town throughout the year. It is not one of our evergreen ferns, but the spore-bearing fronds which remain through the winter are quite distinctive and are easily noticed when there is some snow cover. The photo of these fertile fronds sticking up through the snow was taken at the Benfield land last winter.
(Photo by Kay Fairweather)

Distinguishing characteristics: This fern has two types of fronds - sterile leafy fronds and fertile fronds which are specialized for spore-bearing. The leafy fronds can be up to two feet tall and have around 12 pairs of nearly opposite leaflets with conspicuous veins in a net formation. The leaflets are not finely divided, or lacy, or particularly fernlike. The fertile fronds are shorter than the leafy fronds, about one foot tall, and the spore cases are inside little hardened dark brown beadlike structures. The young fiddleheads are pale red.

Habitat: The Sensitive fern prefers shade but will grow in sun as long as there is plenty of moisture. It is found in wet meadows, along streams and on river banks. It is seldom found in heavily wooded areas. It can be used in natural woodland gardens and as a ground cover in shaded areas. It has a creeping rootstock and spreads and forms colonies. Despite its name, it can survive quite tough climatic conditions and is hardy to zone 3.

Poisonous: I wouldn't recommend eating fiddleheads from the sensitive fern. (Edible fiddleheads come from the ostrich fern.) Sensitive fern has been implicated in the poisoning of horses that graze in low, wet areas. I also found the fern at a veterinary web site in a list of plants toxic to cats.

Reference: Boughton Cobb, A Field Guide to Ferns, published by Houghton Mifflin.

Submissions for the Biodiversity Corner are encouraged from everyone. You can write the column or tell me what you saw and I will write it. The only requirements are that the species exists in the wild and was seen in Carlisle. Send a note to Kay Fairweather at 392 School Street, Carlisle MA 01741 or to

2004 The Carlisle Mosquito