I remember the day I first discovered this attractive little wildflower in my neighbor's yard.  Since he was not a flower lover and I was, I decided to dig it up and put it in my garden, and that's what I did.  I didn't know at the time that its botanical name was Anagallis arvensis or its common names include "Scarlet Pimpernel" (the one I use) and "Poor Man's Weatherglass" because it closes its flowers in cloudy or bad weather.  I just knew it was beautiful and I had to have it.  I have heard some say it is invasive, but for me it was anything but.   I have thought about this flower for years and finally located seeds to grow it again.  Anagallis arvensis, a sprawling annual from Europe that has naturalized in North America, grows to less than six inches high and blooms in summer with tiny coral/salmon/orange flowers that appear singly, each with five petals.  It is easily identified because its color, as seen above,  is so rare in the plant world.  Through the ages, Scarlet Pimpernel has been used for treating all manner of ailments, including melancholy - and how could it not?  Sun, part shade.  Zones 7-10.