Open door policy

It was a turbulent day as a blustery wind swirled around the house and threshed the trees about like a terrier shakes a rat.Now in fullest leaf, their heavy branches swooshed and billowed in the onslaught. On such days I go down into the valley rather than risk the coast. There wasn't much to see and the woods are difficult to negotiate in this season of maximum undergrowth. 

This plant interested me because I couldn't immediately identify it and when I looked at the photograph I found the flowers, enlarged, were curiously attractive. It's common hemp nettle known as a pioneer plant, because  it's one of those 'weeds' that are quick to colonize newly-broken ground, getting in there early before slower species take hold. Once they do, hemp nettle moves on. Accordingly, although it's a native of the Old World, since reaching North America it has spread itself, unwelcomed, across the prairies.

These flowers measure only a centimetre or so but the cropped image reveals the distinctive patterning on the flower's lip, spelling out a message to foraging bees 'Refreshment here!' (The four stamens above are located to catch any pollen carried by the visitors.)
 I would imagine that bees react instinctively to the signal just as most of our own species can recognize MacDonalds' golden arches or the green and white livery of Starbucks without requiring any extra information. Every flower bears its own logo.