This grows anywhere it can get a foothold, and once it's established, it stays put. It's an introduced weed from Eurasia that is capable of holding its own even against our native ferns. It grows enthusiastically on rocks, in gravel, or in the cracks of cement, along stream beds or roadsides. We had it on a solid clay hillside near Mission, and I would rip out great armfuls of the stuff, only to find it growing back a week later.
It confused me at first, too. It's a geranium, related and similar to several other native and introduced weeds;
"consult technical manuals", says my Plants of Coastal BC. Herb Robert is variable; it has an "unpleasant odour", or not. It is hairy, and the hairs may be sticky. Or not. The flowers may be solid pink or purplish, or striped with white. It is quite pretty in the spring, with its fern-like leaves and shining flowers, but the whole plant turns orange-red as the summer heats up, until it is a tangled mass of straggly, hairy, red leaves and stems, with few or no flowers.
It can spray its seeds up to 20 feet. And they will sprout next spring, no matter where they landed.
Why "Robert"? Nobody seems to know. Or rather, everybody seems to know a different reason. Or even a different name; there are over 100. I like "Dragonsblood"; it describes the dry-season colour perfectly.