I have a large pot of mother-in-law tongue plant that summers outside and spends the winter in the master bathroom. It hasn't been repotted for a several years, and the 12" pot was overgrown and completely full. The weather's almost warm enough to take it out to the deck again, but before I did I knew it needed some attention.
I carried the plant outside and dumped it out in the grass. It
was so root bound that it was impossible to see the soil. I turned the root ball upside down to get a better angle for pruning it and two small earthworms fell off, wiggled into the turf, and disappeared.
HOW did they get there?!?
The plant never comes close to the dirt. Each spring I put the pot on the deck (with 'feet' underneath it to raise it up off the wood). It stays there until it's time to come back inside. Because we have a walk out basement and the deck is on the same level as the family room and kitchen, it's effectively on the second story.
After giving the worms' presence a lot of thought I came up with a possible solution. Late last summer we had the deck power washed and re-stained. While the work was done I moved the plants to a concrete slab behind the garage. Either the worm entered through the drainage holes and stuck around for almost six months, or a worm entered and left an egg cocoon, which hatched this spring.
I guess, though, it will always be a mystery.