i have ferns that came from forest in my area. they stay outdoors in winter, in late summer they produce thick dark fronds. is this natural?
Some ferns have sterile (green) leaves and produce central fertile leaves in summer. These may be brown, as in the case of the cinnamon fern. Forest ferns (and it is illegal to remove plants from government lands) must have consistent moisture and shade or they will dry out, turn brown and go dormant. You need to check the ID websites and find out which fern you have. There are thousands of them!