Did a quick research dig, and it's not good news, I'm afraid. There's an old study published in Lancet (1998 I think?) that says these little gizmos aren't terribly useful.

The idea, as far as I can follow it...not my field, is that there's a burst of oestrogen just before ovulation. Increases in blood oestrogen levels DO correlate with incraesed levels of oestrogen in saliva.....the presence of oestrogen does cause these salt crystal trees to form more easily in dried samples. So they're not making up the science of it. The problem is that the results just aren't consistent. Not from woman to woman, in any way...which makes these little toys pretty much useless. What I found kind of amusing was that the study included both post menopausal women and some men as controls...and all the men, as well as some of the women who certainly weren't ovulating had positive ferning. So there are obviously ways to get screaming false positives using this sort of test. Better yet, women who were verifyed to be ovulating (other tests, including basal temperature....that one really is a good predictor of ovulation) showed no ferning fully half the time. So false positives all over the place, and half the time the gizmos miss the real signal. Pretty pointless.

But not entirely pointless, in one very specific and potentially unhelpful way. If you track your ferning pattern over a couple of months, it should stay consistent FOR YOU. You won't know necessarily from that when you're ovulating...but if you find your ovulation pattern with body temp or something else, you might be able to map one pattern onto the other....and then use ferning as your personal road map. But that's just a guess on my part...I'm no fertility expert.

I'm sorry to be the bearer of debunking news....still, everything I read suggested that basal body temp really does tell you something. You might try that?

Best of luck in any case...wish I could do more.

G