Nasty but fascinating. That's the stinkhorn. Jutting from mulch dyed an unnatural burnt sienna, these strange mushrooms provided a bizarre counterpoint to the mundane ornamental hostas growing in this flowerbed. There are three of the stinkhorns in our neck of the woods, and this one, I believe, is Phallus ravenelii, or Ravenel's Stinkhorn.
The stalk of the stinkhorn is called a receptaculum, and the sticky malodorous spores are borne on that terminal cap, which looks a bit like melted chocolate. I could smell these from at least ten feet away; stinkhorns exude a foul, carrionlike odor to attract flies and other flesh-eating critters in the hopes that they'll spread the spores.
I would imagine your average, prim, sunhat-wearing trowel-wielding gardner would gasp in shock and horror to find such aberrations thrusting forth from the petunias. Their disgust would only be compounded by the olfactory asssault waged by glutinous spore masses putting off an odor only a Turkey Vulture would love.
But leave the stinkhorns be, say I. They're certainly an odd twist to otherwise boring mulch beds.