Full flower

Somehow I thought I'd read somewhere that the full moon we had in the week just past was a blue moon, but I was (I know how difficult it is to believe) wrong. Somewhat. A friend just corrected me as follows:

If there are four full moons in a (three-month) season, the third is called a blue moon. That rarely happens (hence, "once in a blue moon"). The full moon waning just now is called a "full flower moon."

But it's much more than that: http://bit.ly/2VKkxP1

(Hint: It's also a blue moon.)