ferns

Fern Phenology Pilot Project: The Sexual Reproductive Window of NC Native Ferns

In his book, The Ferns of Britain & Ireland, Christopher Nidol Page (1942-2022), reminds us that ferns and related Pteridophytes are among the oldest plants on earth. They have lived on earth three times longer than flowering plants and have survived at least four mass extinction events. It would therefore seem worthwhile to include them in our studies of environmental stressors associated with climate change today. Nevertheless, as of June 2025, none of the existing phenological databases are set up to annotate spore-bearing plants. Fortunately, the USA National Phenology Network is actively developing the terminology to do this. 

In March 2025, Walmer Woodlands began studying the sexual reproductive window of four NC native ferns and was fortunate to be invited to collaborate with the USA NPN in the development of the terminology to annotate these ancient plants. 

Species being studied

Polystichum acrostichoides (Christmas fern)

Dryopteris ludoviciana (Southern Wood fern)

Adiantum pedatum (Northern Maidenhair fern)

Phegopteris hexagonoptera (Broad Beech fern)

Protocol

In the first year, each of these ferns is visited every 2-3 weeks at the NC Botanical Garden. The ferns are photographed (whole fern, representative frond anterior and posterior), macro of sori on distal, mid and proximal fronds if present. Measurements are taken of the fern size, length of stipe, blade and length of the blade occupied by sori of 4 of the most mature fronds. It is noted whether there are signs of first growth (fiddleheads), young leaves (partially unfurled fiddleheads) and leaves. If sori are present, a representative frond is collected and stored for up to 7 days to determine if spores are released. If they are the spores are separated from the chaff and cultured following a protocol developed by Brian Aiken, American Fern Society. The length of time from spore culture to the appearance of prothalli (gametophyte) is noted and then the time to first leaves (sporophyte).

The protocol will be followed for three years and an attempt will be made to photograph the fronds weekly around the time that the sori are expected to appear.

The data is being entered into a REDCap database and the photographs are archived with iNaturalist.