What's wrong with my ferns?
I'm not new to gardening but I am new to this forum. I've had ferns in my backyard for about ten or so years and I just love them. Every year for the last five, they develop this weird pattern on their leaves. I am wondering if they are diseased or if something is eating them. My husband thinks the heat gets to them but we haven't had a very hot spring here, so I don't think that's it. Our local garden center thought it could be slugs.
Any idea what the problem could be?
Thank you so much for any help!