Your last chance to see a blue moon until 2015 was Friday. Hope you didn't expect an azure hue in the sky.In fact, "blue moon" refers not to color, but to rarity. Blue moons are defined as either the fourth full moon in a season or, more recently, as the second full moon in a month. It's the second definition that covers August's blue moon; the month's first full moon was on August 1st. I was looking at my "red" calendar I get from City National every year trying to figure out when the best time was to wean my filly by the signs and thought there was a misprint. I had forgotten about blue moons.Blue moons happen because our calendar months don't precisely sync with the moon's orbit. It takes the moon 29.5 days to wax and wane from full to new to full again. With the exception of February, months are longer than that, meaning that once in a while, the timing works out so there are two full moons in one month.Blue moons are best known from the phrase "once in a blue moon" (http:lifeslittlemysteries.com/2776-blue-moon-phrase.html), meant to refer to something extremely rare. Two blue moons in a month aren't all that unusual, however; they occur 2.7 years apart on average, though not with great regularity. The last blue moon occurred on December 31, 2009. That "New Year's Eve Blue Moon" also coincided with a partial lunar eclipse for viewers in Europe, Asia, Africa and some parts of Alaska.Another truly rare event is a year with two blue moons. The last time a single year had two months with two full moons was in 1999. The next time double blue moons will occur is in 2018.All of these dates are based on a new definition of a "blue moon", however. In traditional folklore, blue moons were defined as the third full moon in a season with four (three being the norm). That definition shifted in 1946, when a writer for Sky and Telescope magazine simplified the definition (or got it wrong, depending on your perspective) to the two-in-a-month phenomenon. The simpler definition caught on.If you missed it, the next blue moon will occur on July 31, 2015.Someone was talking about Eryngo over on the Old Mason Road. I have called it many things (some unprintable!), but it's nice to know the real name. Tony from over that way thinks it is gorgeous and it is one of his favorite natives. I can remember my mother drying it. The purple color stuck around all winter. It seems regal somehow, don't ask me why. Maybe it's that crown on top?The clammy weed in the river bed is stunning right now. With the setting sun behind it showing off the red finery, it becomes magical. The goldenrod is starting to bloom. This year seemed to bring an abundance of black widows. I've never encountered so many. It's funny how you don't think that you can identify spiders just by their webs, but a black widow's web is distinctive and everybody recognizes the argiope spider's zig-zag stitching.The deer seem healthy. Some pretty impressive groups of bucks are hanging out together. That will change with the first cold snap, like boys in junior high suddenly discovering that girls aren't so bad after all. I have been seeing turkey flocks, so they are on the move. The abundant grasshoppers should help both these birds put on some layers of fat to help them through the winter months.The Texas persimmons have started to ripen. Delicious! And that's not just my opinion. Every varmint, deer, bovine and bird in the woods seems to have their head stuck in or under a persimmon bush. I thought my dog was trailing something really intriguing under those bushes the other day until I figured out she was eating the fruit.Also the tunas on the prickly pear are ripening. You will have to look quickly though, because the hogs love them. It took me awhile to figure out that sound when traipsing through the brush to come upon feral pigs feasting on tunas. It's something like an episode from "My Big Redneck Thanksgiving Dinner".Things are happening in the Hill Country so go outside and play!