I'll admit, I checked GameFAQs too for runey info. It's rather confusing in-game (runeys eat other runeys? sometimes runeys are added for no apparent reason? sometimes they DON'T eat each other? what???), and not explained well. And yeah, I did read about them in the stupid library. What did I come away with? "Runeys make stuff grow, so watch out!" Lame.
It IS worth it to watch out for them, though. All my crops grow faster, even in dungeons. Heck, I have strawberries every day. Harvest them, water the plants, and next day they're back. That's twice as fast, or double your income if you harvest them every day.
Unfortunately, with no way to grow them in winter, all my areas took fairly major hits. Now that it's spring again, Operation Runey "Runewal" is beginning in earnest.
Also, I've logged... slightly embarrassed... nearly 100 hours in this game. =o It's basically all I've played since I got it several months ago. That's value, folks!