Think Death Valley and you think desert, with an average rainfall less than two inches per year. Yet the ecosystem is surprisingly diverse, even including wildflowers. And in a year of above-average rainfall, the desert can spring to life with such a profusion of flowers it’s known as a superbloom.
Seeds can lie dormant for long periods. Wildflower seeds also have a coating so just a touch of moisture will not cause them to germinate. On the contrary, the rainfall must be adequate enough to support the plant throughout its entire life cycle. In other words, if there isn’t enough moisture for the plant to live long enough to produce another crop of seeds, the coating won’t dissolve.
Once in a great while, there is a generous rainfall, so not only do seeds close to the surface germinate, but seeds dropped years before and that have ended up much deeper also have enough water to come to life. Hence the superbloom. This happens to be one of those years.
For a more-complete explanation, watch the video: “Superbloom: How Death Valley Springs to Life” at http://www.sciencefriday.com/videos/superbloom-how-death-valley-springs-to-life/. The Science Friday podcast for April 1, 2016 provides an interview with filmmaker Christian Baker.