A noxious weed.

This is a noxious weed, indeed.  And the bane of the Vinodogs.  The spines on the fruit of the puncturevine (Tribulus terrestris) are apparently tough enough to puncture bicycle tyres, not to mention the soft little pawsies of my girls.  This wretchedly, sneaky weed has a prostrate growing habit, so I often don't notice it until a Vinodog comes to an abrupt halt whilst on a walk, pathetically offering up an afflicted paw for help.  Each fruit separates into 5 vile, wedge-shaped burrs and it is the spikes on these that are so treacherous.  Although the burrs may look somewhat like a botanical mace, the weed does not wield them like the medieval weapon, but rather uses them as a device by which to disperse seeds - in tyres, on clothing, or on the Vinodogs.  Ouch!  
In summer these weeds are nuisance enough.  But even in winter, after the plant has died, these nasty little burrs remain on the dried stems, or on the surface of the soil, lying in wait for some poor, unsuspecting soul.  Or at least they were.  Vinomaker was kind enough to don a pair of heavy duty gloves and pull out a few puncturevines he found by our mailbox.  The Vinodogs, and I, thank you!