No one planted these cosmos, at least not on purpose.
Their parent plants weren't even in that area -- they were about twenty feet away on the back bank. But seeds were shed onto the pool deck, and subsequently swept, along with redwood needles (top right) and a euonymus leaf (top center) to a plantless little place down at the far end of the pool under the grapevine.
Through the dry autumn and winter, there was nothing growing there. But one rain storm, and here are little survivors venturing into the sun, green and already sending secondary leaves out.
I cleared the weeds in that part of the garden, leaving all the cosmos and all the California poppy sprouts. And I just happen to have a spare emitter from my irrigation system that will reach them.
I can't wait to see them blossom pink above the poppy orange.