Onions that came up on their own

These were in the garden, growing from seed apparently, completely unexpected:

I love it when things just "show up" in the garden.  It's such a testament to life and the perseverance of nature.  Last year our neighbors had "volunteer" tiny white pumpkins grow out of their compost.  Our cilantro self-seeds all over the place, so does our dill, and this year we have volunteer lolla rossa lettuce in our broccoli and cabbage space, growing happily among the brassicas.  But this summer these two onions were the biggest surprise.  I've had lots of trouble with trying to grown onions in the past.  I planted from seed in the basement, they were spindly little things when I planted them in the ground, and then they grew only slightly larger than a marble.  But, in true mother nature survivalist form, one must have produced seed, because yesterday, in with the wild garlic in the herb garden, we found these two onions, both bigger than golf balls.  Once again, like the wild raspberries, no fussing no tending - and here they are, bigger than anything I've actually tried to grow!  Now that's too funny!