Strawberries- For the heck of it we planted four strawberry plants (bushes) just to see if we could get enough for a good desert. That was 5 years ago. One plant didn't survive the first year because I ran over it with the lawn mower. By the end of the following spring we had 9 strawberry producing plants. However as with the first year we only got to sample a few strawberries. Our local wild fauna took care of the rest!
That fauna also proved what we all learned in high school biology- animals eat the berries and deposit the seeds in various places when they shit. We now have so many strawberry plants that I haven't stopped to count them. All of the original 4 are long gone and their place is now just grass. No sign they were ever in that spot. Our neighbors have strawberry plants. There are strawberry plants by the sides of the near-by roads. And our flower garden is now also a strawberry field. The black-eyed susan population has been severely diminished. There are strawberry plants by the shed. Strawberry plants amongst the weeds.
Strawberry math: 4 strawberry plants - 1 strawberry plant + strawberry lovin' critters = strawberries plants for the neighborhood
And don't get me started on the raspberry bushes we planted...