Hi Marydean

I have been using MB for six months now but do not use it all that often, I have never ever seen 'ferns', when I got my +OPK I did it the next morning and the whole lens was covered in a pattern that I had never seen before but was definately not ferning.
Can't really answer your question though, maybe just try doing different things, more saliva, less saliva, maybe even lick the lens instead of smearing it on.
Goodluck Marydean, hope you get your BFP soon.

Julia