According to park signs, this and other prairies in the south Puget Sound area formed after glacial meltwater, from the ending of the Ice Ages, washed up a lot of rocks and created some areas of very rocky soil that don't hold water relatively well. Later, during a warm period (10,000ya-4,000ya according to the park) prairie plants established themselves. After that, a wetter and cooler climate occurred, but the prairies were already there and maintained by local Native Americans, who burned the prairies to preserve camas habitat (the bulbs are edible).
Maintaining a native environment like this takes work, particularly in the wake of human disturbance and introduced species. While I was there, I saw volunteers yanking invasive plants out of the ground. Signs described how, in 2009, some Douglas firs were removed to allow Garry oaks to grow. Even before white settlement, native residents burned many prairies regularly to keep forest from encroaching.
There were a few camas blooming, though most of those flowers have yet to bloom in the park.
The real highlights were the shooting star flowers blooming all over the park. Here are the best pictures I took of them. Like camas flowers, these shooting star were too short for the use of my tripod; therefore, all of the pictures you see (in fact, all of the pictures I took at the preserve) were handheld.I was also able to use my wide-angle lens for a shot. There is a little patch of dandelions growing along one of the trails in the middle of the park. Given how bright the sky was, it turned out better-defined than I had expected. I used an apterture of f/16 to get everything in focus. Were I to edit it, I would probably brighten up the foreground a bit.
There are also a lot of early blue violet (Viola adunca) blooming. Some of the flowers looked a bit motley - they seemed to already have been blooming for a while - but I found some nice ones. I'm finding more and more that I have to be very picky with the flowers I photograph close-up. I took a couple of camas pictures on Saturday, but ended up displeased with them. One of the flowers only had five petals (instead of the normal six). The other flower had all six petals, but some of them had holes and bites out of them. Everything "worked" in those pictures' technical respects, but the characteristics of the flowers themselves ruined the images.