The bloom shapes don't look like any of my Watsonia - perhaps it's Crocosmia.

Very probably Crocosmia - and is easily moved by running water. Particularly the corms. They happily grow in shingle on river banks.

The corms are like a string of beads in the ground and be quite hard to dig out as they can go down for at least six inches.

Watsonias tend to clump more and have bigger flowers. The leaves can reach 36" long. More likely to flower in spring. Crocosmia is more likely to flower in summer and autumn for us. (Currently flowering here - late Feb - and it's late summer.)

I found it! I was perusing a Van Bourgondien catalogue, and there was a picture of the plant I was trying to identify! I looked it up, and you are correct - it is a wild crocosmia called crocosmia mansonorum. It is really blooming right now - all over our town, in almost every vacant lot and next to the street everywhere, where I assume the bulbs were washed by water going down the gutters. This makes sense, as our climate is Mediterranean, which I assume is similar to its native climate in South Africa. Mine had already spread in that bed to two other places, so I dug them up and just left the original patch. I am sure next year there will be more of them! I like them because here they bloom in the very early Spring - mine started at the end of Feb, and continued through all of March and is still blooming now in the middle of April.

Jackie

Chasmanthe floribunda

Chasmanthe? Can be invasive.