I’m uncertain if Colchicum, sometimes called autumn crocus (Colchicum autumnale), spreads readily from seed, but that would explain a small clump several feet downhill from ones that I most definitely planted. It’s possible that I planted the scattered few. I cannot be expected to remember everything I’ve planted, but if I did, the skimpy result is disappointing. I think these are hard to kill, so probably the scattered flowers have resulted from seed.
The autumn flowering Colchicum is a short lived bloom, as is the late winter flowering Crocus, and though the appearance and briefness of the flowers are similar, the bulbs are not related. I plant only a few of the winter bloomers since squirrels carry most of them off, but from my limited experience the flowers of autumn Colchicum are considerably larger. Also, in case you are tempted to nibble, Colchicum is poisonous, so squirrels and deer will not be to blame if they disappear.
The flowers are a delight, even if they don’t stay around long, and if the few lonely blooms have come from seed, better still.
Happily, there are many other seedlings in this garden. Dozens of hellebores have been transplanted, as have toad lilies. At any time, there are dozens, many dozens of Japanese maple seedlings of varying leaf colors and shapes to be found. Most are discarded or the garden would be overrun, but some have been dug out and potted, and in time I’ll see if a worthwhile tree develops.

Many ferns have sprouted, mostly from Japanese Painted and Ghost ferns, but also native Sensitive fern. These don’t get in the way except for the few that grow between stepping stones, so most are left to grow on, and only a few are transplanted. I can mostly recall ones that started as seedlings (or sporelings for ferns) from ones that I planted, though ones from seed (or spores) are most likely to have sprouted in advantageous spots.