I've been dealing with Azolla caroliniana for decades, either growing it or trying not to grow it, but this is a new one on me! I have some in a large outdoor aquarium which is part of my rainwater storage set up that I grow water plants and breed fish in over the summer. I often use the water from the tank to water other plants in my collection, including a few that are kept in a birdbath which acts like a water tray. I just noticed these strange looking clumps growing in my Bog Lily pot, and at first thought they were a Liverwort. Upon closer inspection it turns out to be the Azolla. I never knew it would grow terrestrially, but a bit or research confirmed it.