Sporangia are confluent and parallel to the midrib. Deer fern reproduces from spores and by sprouting from rhizomes. It is an indicator of hypermaritime to maritime subalpine boreal and summer-wet cool mesothermal climates. Disturbance in these cool, wet forests is generally from windthrow or logging. Along the west coast of Vancouver Island, British Columbia, deer fern may be present in young seral stands in floodplain succession.
Fire is infrequent in the cool, wet forests in which deer fern is found.
Fire intervals are estimated to be several hundred years. Deer fern may colonize sites after small patch fires by spores or the spread of rhizomes from adjacent unburned areas. Deer fern is probably top-killed by fire. Rhizomes may survive light surface fires. Information on the response of deer fern to fire is sparse.