It does not happen often. The average frequency is about ten to fifteen years. However, it occurred in both 2017 and 2019, prior to this spring. That is enough for thirty to forty-five years! The current superbloom is only now finishing locally. It may continue through most of May near the coast farther North. The best bloomers enjoy the Mediterranean climate.
Climate is the typical and seasonal weather pattern of a region. The local Mediterranean climate is typically mild and somewhat arid. Almost all rain occurs between late autumn and early spring. Rain is otherwise rare. Winters are cool but not too cold. Summers are warm but not too hot. Native and some exotic flora knows how to exploit such climates.
Some exotic flora that prefers other climates also seemed to demonstrate a superbloom. Some merely responded to the unusually cool weather last winter. They appreciate more vernalization than they typically experience here. Some species enjoyed the unusually abundant rain last winter. Some species enjoyed both extra rain and extra vernalization.
Native species and exotic species from similar Mediterranean climates are a bit different. Their superbloom happens at the same time, and is also a response to earlier weather. However, it is also a response to later weather. They know that Mediterranean climates get warm and arid through summer. They are in a rush to finish blooming while they can.
Superbloom is how many species accomplish all their annual bloom within a brief time. They begin as soon as cool and stormy wintry weather finishes. They finish before warm and dry summer weather desiccates their flowers. Of course, such bloom may not be so spectacular after typical winters. It is only superbloom after exceptionally wintry winters.
Some species that exhibit superbloom in the wild bloom later for irrigated home gardens. This includes some exotic species from similar Mediterranean climates elsewhere. Such climates are present in small portions of Australia, South America and Africa. Obviously, most Mediterranean climates are around the Mediterranean Sea. Most exotic plants that are most adaptable here are from such climates.