Ferns in Winter
One does not think of looking of ferns in the winter. However, there are several species in New England that are green all year long. Collectively these ferns are known as evergreen ferns (formerly wintergreen). This not a taxonomic designation, it is a trait designation.
Three of the most common evergreen ferns are Christmas Fern (Polystichum acrostichoides), Evergreen Woodfern (Dryopteris intermedia), and Princess Pine (Lycopodium obscurum). The last, Princess Pine is not a 'true' fern, but a lycophyte.
Christmas Fern (Polystichum acrostichoides) does not look as 'robust' in the winter. The fronds lay down on the ground. They develop brown spots, but they do stay green.
Evergreen Woodfern (Dryopteris intermedia) is very healthy during the winter. It is also a good time to find out exactly which Dryopteris species one is looking at. The other wood ferns that can be confused with Evergreen Woodfern are not evergreen.
Princess Pine (Lycopodium obscurum) sticks out of light snow fall, looking like miniature Christmas trees. Easy to spot. Still bright green and healthy.
Stems and Fertile Fronds
There will be brown stems from ferns that have withered in the fall. A few species will still have their fertile fronds standing high above the leaf litter.
Sensitive Fern (Onocelea sensibilis) and Ostrich Fern (Matteuccia struthiopteris) both have fertile fronds that winter over. These fronds both stand about 1-2 feet, 25-60cm above the ground. The fronds are distinct so there is no confusing one for the other. They are a definite sign that one will find healthy ferns in this location in the summer.
Tufts and Other Signs
After not finding evergreen ferns, or fertile fronds, there are still signs that ferns will appear at a location in the spring. Look for tufts with brown stems. The tufts are the surface signs of the rhizomes. Some tufts are very dense, others are loose. If one finds tufts there will definitely be healthy ferns in the spring.