Q: We have a Macho fern that we bought last summer and it was doing great in a pot on the front porch, we brought it inside for the winter and it did very well. Now for the spring we decided to place it in the ground because it was getting really big and we needed the pot for a new fern we purchased. Ever since it has been placed in the ground it has been slightly turning brown.
A: I think it’s sunburn damage.
The light levels you had the plant under indoors are ten times weaker than those outdoors.
When the sun hit the fronds, it fried the tender plant cells and they turned brown.
The fern may recover and send out new foliage but I wouldn’t hold my breath.