It is impossible to say how long native wildflowers have adorned the natural landscape of California. Various lupines, California poppy and evening primrose had always been the most colorful wildflowers locally until they began to be displaced by exotic (non-native) plants only in the past two centuries or so. Although natives are remarkably resilient to dry summers and occasional wildfires, they are not very competitive with more aggressive and prolific invaders. What the natives and exotics have in common though is that they are so well adapted to local environmental conditions that they are able to perpetuate without much help.
Lupines, poppies and evening primrose, as well as native yarrow, godetia, and fleabane, may unfortunately need a bit of help if exotics want to move into their territory. In areas that are regularly or even only sometimes watered, weeding to remove more aggressive exotic plants helps the natives stay in control. They should otherwise do well on their own. Although without irrigation their growing season is much shorter, natives are slower to be displaced, since so many of the otherwise competitive exotics are not adapted to dry summers.
Many exotic flowering annuals are prolific enough to almost become naturalized, but are not quite aggressive or adaptable enough to get very far from cultivated landscapes. Cosmos, nasturtium, alyssum, catchfly (silene), four o’clock, gaura and foxglove self sow so readily that they are considered by some to be invasive. Some of us instead consider them to be ‘reliable’. They can be useful for unrefined parts of the garden that we do not mind watering, but otherwise do not want to put much effort into.
However, foxglove and even nasturtium can actually become noxious weeds in coastal areas not too far from here. I think that forget-me-not, feverfew, baby tears and English daisy can be problematic anywhere that they get enough water. Also, most annuals eventually revert to more genetically stable forms; which is why all varieties of dwarf nasturtium eventually bloom with the same yellow or orange single flowers. Yet, if we can distinguish between the plants that we can appreciate for their reliability and those that can be too invasive, native and exotic wildflowers and not so wild flowers can make gardening a bit easier.