If you come down to California, you'll notice that there are different types of vegetation the closer you get to the ocean, and different types of vegetation on north facing, west facing, and south facing slopes. The vegetation change with elevation is also quite profound, especially on the eastern side of the mountains where there is desert. This all has to do with temperature, sunlight, elevation, and water availability. Areas near the coast are cooler and a bit more humid, so plants that love cooler temperatures and ocean influence, like sages, are found often there. Further inland, things become hotter, so plants better adapted to hot conditions thrive there.
The slope effect has the most profound and easily observable effect on California's vegetation. North-facing slopes receive the least sunlight, and consequently they are cooler and more moist. As a result, forest-type vegetation consisting of both evergreen and deciduous trees dominates:
South-facing slopes and open areas receive the most sunlight, and are consequently the driest. In Northern California, they are often grassland with the occasional oak tree, and in Southern California they are oftentimes dominated by low-growing shrubs (the rocks you see in that picture are tailings from old mining operations):
West-facing slops are sort of an intermediate between north and south facing slopes. They are often dominated by shrubs such as coyote brush and manzanita:
As you get higher up into the mountains, things get more moist, and a community of shrubs called chapparal dominates. As you get even higher, pine trees begin to emerge out of the shrubland, and eventually you have a forest of tall pine trees:
As you go down the other side of the mountain towards the east, things get increasingly dry. Due to the rain shadow effect, there is very little rainfall on the other side of the mountains. The result is scorching hot desert with much less vegetation than on the coastal side:
Generally, water is the key determining factor of what vegetation grows where in California. Even in the deserts there are lush riparian forests growing next to streams.
I'd love to check out Washington sometime too. I love the forest just like I love California's Mediterranean climate. It would be interesting to see what kinds of smaller plants are growing in the little nooks and crannies there. You guys also aren't short of water like we are.
